Hearing you talk about that GM "151" cam made me smile, It was my number 1 choice for my pump gas street engines in the early 70`s. In the early 90`s I used the 292H Comp cams for that lumpy idle the guys liked and it run strong in a 350. One of the old guys I worked with when I was a pup told me to assemble the long block on the stand put a starter on it and starting at straight up take a compression check then advance the cam and take another compresion check and stop when you got the highest reading, it worked surprizsngly well. Them old boys know there stuff.
I spent my whole life around drag racing and build blown fuel engines for a living. This is really really good content. Touching on things most enthusiasts don’t understand 🤘🏽
It never occurred to me that the cam would directly affect compression, but thinking about it it makes total sense. Many years ago (1985), I had a 1972 Oldsmobile with a 455 that appeared to be stock. It had plenty of torque and was fairly good on gas. I always ran Sunoco Ultra which at the time was 93 octane and it ran great on it. I did cranking compression test on it and got between 185 and 205 psi. It also had nice idle and the stock GA heads typical for ‘72 455s. Thanks for the great presentation, you got me thinking.
I ran well over 13:1 on pump gas. I did not build this engine to run on pump gas. I purchased a used 406 short block and was going to put my top end on it which consisted of a set of AFR210's and a port matched Victor Jr. with a Race Demon 835. The 406 turned out to be junk and I already had a camshaft made for it for nitrous. The compression of this 357 smallblock was well over 13:1. The pistons were Ross 91461 with a 15.2cc dome, it was zero decked, the chamber size of the heads was 66cc and the head gasket was 0.040" thick. The cam was 268/274 @ 0.050" with a 108ICL, 112LSA and 630" lift. I ran it on the street and raced it on the track with nitrous. After running it for a while I did a cold compression check and it came in at 195-205. This was lower than my previous 355 so I ran it on 91 octane pump gas while on the street and race gas when I took it to the track. Race weight was 3,420 and it ran 11.20's at 120 on the motor and Ten teens at 132 on a 175 shot.
I remember reading an article in a Chevy Hi Performance magazine where some automotive school was tasked with trying to make 700 ft lbs of torque on 87 octane. They ALMOST succeeded except for a mechanical problem with a spiroloc missing. The build was a 502 BBC with hypereutectic pistons having a CR of 12.5:1 and the engine having a special flat tappet grind and including Feuling aluminum peanut port heads with small chambers. I believe they used a Holley street ram efi setup along with an aluminum radiator filled with Evans NPG coolant. The motor ran fine until the wrist pin on one cylinder worked its way into the side of the cylinder. I recall being amazed that such a high CR could be utilized on 87 octane. I wish these greedy petroleum companies would produce just one street octane of like 95 or thereabouts. Europe only does one octane to my understanding. Thanks for a great video.
It is a Chevy engine, my respects; I’m mopar small block, but you explain it so simple I respect you, and every one no matter what brand!!! The knowledge you have some humans don’t understand that did not grow on roses over a few nights!!! Thank you so much for this serious and true information!!
Its bc all pushrod v8s are very similar... So things I say about an ls or sbc I can say about a Windsor mopar Pontiac Olds to a lesser extent hemis and semis
I don’t think most consumers and average enthusiasts understand that dynamic compression is what matters and yet all you hear about is static. Great video!
Like yourself, I am a student of David Vizard. I believe you are spot on with everything that you have stated. I’m currently building a 400 sbc for a ‘70 Camaro using a lot of David Vizard’s principles. I thoroughly enjoy your videos, so keep them coming please! Thanks for all your efforts.👍🏻
In about 1992 I had a 68 Camaro daily driver with a .30 over 454. I had a .250 domed piston, with a Comp Cams 292 Magnum cam. 244 at 50 and .556 lift. The cranking compression was 225 lbs. on average! I used a stock converter, Turbo 400 trans., and a 4:10 12 bolt rear end. I drove the car on premium fuel at 91 octane. I had to dial back the timing to stop detonation. It wasn't an ideal combo for the street, but it was a beast! The widest tire you can run on a 68 Camaro is 11.5 inches. That's what I ran and the Hoosier Quik Time street tires couldn't hook! It was a ball to drive!
Thanks Rick. That would be a beast for sure. You were definitely pushing the limits of pump gas and also it makes me think i am being conservative with my 180PSI target for street engines. AG
@@goldsgarage8236 Less compression and or more duration on the cam would have been better for a daily driver. The car ran a best of 12:31 at 114 m.p.h. at the track. My best 60 ft. time was a terrible 2:19, because of loss of traction! I never did run it on slicks. In 4 years of street racing I only lost 3 times, and all 3 cars were running either nitrous or blowers! I never lost on the motor only. I was the only true daily driver racing at the time. The Camaro was my only car.
Aiming for the 160 psi cranking compression mark compared to the 180-200 mark depends on a lot of factors. Having extra leeway for detonation resistance is a good thing but it trades off a bit of power. The person that might not have the knowledge to monitor that they might be more prone to engine damage in certain circumstances (like a particularly hot day), should probably have a bit more leeway for their car. The vehicle it's going in plays a roll too; lighter cars with shorter gears are going to be less prone to detonation too. Then there's also the little things in the build; like smoothing out edges in the combustion chamber, quench, piston style etc. All great information. Great video
Thank Troy, the problem I have with building engines for others is that i have no control over these things once it is off the dyno. i worry about them all. Thanks for your input. AG
Thanks for throwing this information together in such a concise video. I've always known a cam, or cams have direct influence on dynamic compression, but the point you brought up about how quickly the cam acts vs the duration is interesting. I like how you broke it to a ratio. Simple. Subscribed.
Thank you for explaining that so easily and precisely. As an Automotive machinist, I have tried many different engine combinations with compression ratios, from using frquencied inlet manifolds to boost low and midrange torque, to camshaft s with various duration and split etc etc. Yes you can run 12:1 + on pump gas and still have a great performance with the benefit of great fuel mileage to boot.
I’ve watched a few of your videos and I like your approach to things. I don’t always agree, BUT, at the end game I understand your position. When you dropped the David Vizard bomb, I was like …. ok… we’re on the same plane and path! I’ve been a Smokey Yunick guy from the mid sixties on. I would bet most us from that time, that he had an influence on us, regardless of the brand. Really like the channel, well done.
I ended up getting 9 years out of a comp extreme 4x4 cam and Rotella oil. I used the truck for daily driver and off road adventures. At the 9 year mark it started chewing up a lobe on #4 and I had to sell the truck as I had no $ to fix and it was no longer practical for me. Thanks for the no flare no bs info, when you said thats fine we don't have to agree you got me.
The late, great Joe Sherman once said if it pumps under 200psi, it'll run on pump gas. I've ran 13-1 engines on 93 octane on the street, of course I used racing fuel at the track.
My 1998cc Alfa Romeo Spyder (mechanical direct injected) is running 16.5:1 corrected CR on unleaded premium (92 octane 100% gasoline) pump swill and has been for 41 years. It is a Hemi head and it turns 16,000 RPM (peak HP at 12,600 RPM) , but Alfa was building engines that turned 10,000 RPM RELIABLY before WWI! BTW, the Alfa engine has NO valve springs-it uses desdemonic valves with followers (forks) that push open and pull the valves closed. It also has a Magneto Marelli magneto and surface electrode spark plugs that whines like a turbo, driven by the crankshaft. The clock is showing 180,000 Km and it doesn't use any more oil than when new (about a liter between changes, normal by the owner's manual). The four-banger holds 7 liters of oil WITHOUT filter or nearly 9 with filter (big oil cooler built-in).
Big American engines with long strokes cannot reliably turn over about 6000 rpms in somewhat stock configuration. I have no idea what affect extremely high engins revs have on pre-ignition. Most stock engines sold in North America are around 89mm stroke. A $40,000 full custom race engine for circle track use will usually be 6.7 to 7.6 liters, roughly, and they are usually around 100mm in stroke. These engines will run several thousand laps in a year, and they will have acceptable reliability at around 9000 rpm maximum rotation speed.
@@kevinkelley3657 i have a 427 that I run it at 8500 rpms it's a aftermarket Dart aluminum block and 12/1 compression I run M1 methanol and a 98mm forced Inductions turbo point being you can build à reliable engine to turn rpm mine is a small block but that's all that I will give out Openly on here I still race so I'm just saying you can you just have to get the right parts and engine builders I go to tkm there the best in the country.
@@Wardaddy1124 I said in my comment that "custom engines" could turn 9000 rpms reliably in a circle track engine, for one year...........I said that these engines were usually around 100mm in stroke. If you disagree with me, what is your exact argument? I have a VERY good friend who is THE machinist to use in this are........I also understand what aftermarket heads are capable of doing. I am not sure that I understand your argument, but if you have $10k to 15K to spend in parts, you can absolutey build a 9000 rpm chevy based engine that should live for 40 races on a round track under 1/2 mile in length.
If did the calculations correctly (as you say at the end of your video) then, my Comp Cams "Low Shock" cams on the cam card are showing an Advertised duration of 276*/282* and 246*/252* shows 1.12 for the Intake and 1.11 for the Exhaust and according to what is being explained in this video it sounds like my cams have very aggressive ramp speeds which I told them I DID NOT WANT---I specifically told the tech from Comp Cams that I wanted their "Low Shock" cam profile design with easy, smooth, non-aggressive ramps. I guess they didn't get the memo!!! I will send them back! Thank you for your video and detailed explanation.
I agree 180 compression minimum. I target between 185 to 200. But that's not written in stone. All kinds of factors, cast iron heads, aluminum heads. Cast heads static lower. Duration @.050, gears, tire size. And finally, the customers ability to tune the combination. Conservative is good always. But pushing the envelope requires knowledge and experience, not guessing. And I have not even got into carburetors and Fuel Injection. Pump gas, compression up, timing back. Like I said, not written in stone. And a learning curve, always. Great topic. Thanks for sharing. Take care, Ed.
I was loking at the comments and failed to see anything negative or disrespectful so my respects to everyone who chimed in. I totally understood everything you spoke on; however, I am going listen again another time or two. My theory is akin to reading a book, one learns stuff that was missed during the first read, or perhaps something becomes more clear. Thank you for making this video. By the way, the GM Duntov or 30-30 cam was my favorite cam. I would set the lash at 26-28 for more low end torque.
Makes sense. I’ve never looked at it like that so it’s a new concept of thinking. I’m always building drag engines with no vacuum and making all the power up top.
I respect what he just said about David Vizard. And that's the way it should be, he sees a lot of points and recognize that David knows a lot of stuff, however we all have different ways We've Come To What We do. I've been building high performance engines for over 20 years and I still learn and listen to different people. And just because I don't exactly agree doesn't mean they are necessarily wrong. We're too busy trying to show up each other and sound like we all know what we're talking about and are complete experts that we're not open to other opinions. Sometimes two people can have different ways to get to the same end result. And to become better at our craft the things we all love to is having our ears open and listening to others who also know what they're doing. You'll learn and take the best of each thing and then with actual application of your own you learn yourself what works the best for you
Answer to your final question, while I'm only guessing, I'd say low speed and load maybe, depending on many variables. But as RPM increases the addition cylinder filling would send cylinder pressures way beyond what 87 could resist. I built an 11.6 to 1 408 small block with cranking pressure of 217. It's a tight quench motor with aluminum heads. While it runs very well on the primaries, 93 octane (tunnel ram) it does rattle @ W.O.T unless I use race gas. I think it's because of the same reasons stated above. Backing timing low does not help. My W.O.T AFR is fat as well @11 to 1 so i don't think it's a lean induced rattle. Although I can not rule out poor cylinder to cylinder AFR. Love the tech by the way. I'm always looking to learn more, thanks.
Thanks Bobby, you are braver than me but it sounds like a very nice engine. I am planning to address the points you mentioned on a follow up video so thanks for the input. AG
The old GM solid lifter cams had the valve timing and overlap to manage DCR. By closing the intake valve later it allows the SCR ie 11.00-1+ to bleed off cylinder pressure at low-mid rpm when the engine is more susceptible to detonation. Intake valve closing event is a huge factor in engines running 12.00-1 on pump “Premium” by lowering the DCR. Aluminum heads, rule on max DCR for 93 octane is 8.70-1… but many push it to the edge at 9.00-1 but be warned.😉 Iron Heads the max DCR for 93 octane has to be below 8.70-1, I haven’t found any data to share but I’d think less than 8.50-1 DCR
Thanks Headflowinc. I am planning a follow up video on this subject. Thanks for reminding me to include the issue that engines are more vulnerable to detonation at low speeds. I have researched info in this subject.
My 2018 F150 with the 5.0L has 12:1 . It can be run on 87, but I run 93., previous owner of 67 GTA fairlane 390, 70 cougar, 351W & 79 Mercury Capri with 351W with 289 heads ... Did Not like anything less than 101 octane. Ultimately the engine died from pre-ignition. Great video Sir.
On a 350 Cid truck engine with 422 442 cam 204 214 at 050 dur. 112 lsa. Would a 194 intake valve size be a better choice for velocity and low speed torque. I want to buy some Brodix 180 heads but maybe that's a little too big and I want good mpg. Flat tops .020 down. Quadrojet with factory aluminum manifold.
Thanks for your question Jacqueline. I don't think the Brodix heads will hurt, but they are more than you need to work with the rest of your parts. If cost isn't an issue you could use them but there are less expensive heads that will work well. Hope this helps. Good luck with your build. AG
I sent my cam in to a custom grind shop. Im building a stock FE 428 stock dish 4.13 pistons. After I got the cam back he said to keep compression lower than 9 to 1 and use a stall 2500 converter. Putting it in my 72 f250. Just now learning about cams. Just got my new pistons. Im seeing on my cam info card that intake V Closes at 38 ABDC. I need to assemble the rods n pistons to see what comp height is this week. I think the cam he sent me would raise the compression up if i understand correctly. My heads are 72 cc and gasket .o42. This is my first home built short block.
Thanks Ed, looks like that cam IVC is a good match for 9:1 CR. After you determine the deck height, you will have enough info to calculate the dynamic compression and cranking pressure. The Wallace racing on line calculator works pretty well. Good luck and let us know how it turns out. AG
Thank You. Oregon Cam here in Washington has been building cams for ever. After I do some measuring I will send him another core. I have quite a few here.
My 467 has 10:1 static compression, and 200psi cranking compression. It runs on 91 octane with 36 degrees of timing locked out. No pinging ever. Also, I recently tested Shell 93 octane. It had 7% ethanol. And I also contacted Shell Canada about ethanol content in their 91 and 93 octane fuel. They replied just today that their 91 and 93 now contain up to 10% ethanol.
That is good information Pockets, Here, there was a sticker on pump saying that 91 contains no ethanol. I will check again. Thanks for the comment, please keep watching. AG
Years ago I rebuilt an LT1 in my 70 Z28, although at the time I was led down a path of lowering the CR, I think stock was 11 or 11.5:1. When we were done I think I was around 9.5:1 and at the same time the GM performance handbook on LT1's listed a offroad cam for the engine, at the time Crane built one to that spec so I installed it. The engine never ran right so I called Crane and the first question "what CR are you running?" He said you need a minimum of 11.5:1 to run it. So I had to pull out that cam and replace it with a lower duration hydraulic. Now for my question; I am about to embark on a Ford 351w build with a brand new 4 bolt block. I am also making it a stroker 408ci. I do not want the high HP but I prefer a high torque motor, it's going in my '85 Jeep CJ7. Two things I would like to know; If I run E85 or 91/2 octane what CR should I shoot for? Also what off the shelf roller cam should I pick? Thanks in advance!
Thanks for the question Dave. With a roller cam, you need less duration, but you have lots of stroke so duration in the range of 210-220 degrees @.050". With 91 octane fuel, 10:1 CR with cast iron heads and 10.5: with aluminum heads. Design for a max cranking compression of 175-180psi. you can find on line calculators for static and dynamic CR and cranking pressure. I don't have any experience with E85 but I think you could run higher CR and cranking PSI. Hope this helps. AG
Great video. I run a w30 4spd cam in one of my 455s and it has 329 duration they are lazy cams compared to todays grinds because of the ramps. But are easy on valve train.
I have a fast ramp cam and heavy springs in my olds 455 and it beats the tar out of the valvetrain especially those ridiculously long pushrods are definitely bowing.
Combustion chamber shape has large impact. One extreme example is the Jag HE V12 engine, has a pocket in the combustion chamber that's 11.5 to 1 on pump gas back in the 80's. Also today's modern heart shaped tight quench wedge shaped chambers are more resistant to detonation. Also good spark control off the crank shaft helps. This is a particular problem on the SBC with it's dist far back and at the end of the cam... that make the spark bounce around, that's no good and that variation can cause erratic spark and trigger detonation. Crank triggers are a must with high compression.
I struggle with small block mopars trying to make them run smooth. I put on a set of "fast burn" heads, heart shaped modern design and Wow, what a change. Best small block Mopar I have ever seen.
Having quench rather than open heads has huge impact on how much compression you can run. In Australia our standard 430hp 351c, which I still have in an XE ESP runs flat tops, 302c heads opened up to 66cc’s, F246 cam, Weiand excelerator, 750dp, good extractors straight thru mufflers which make 430hp at 200psi dynamic compression. No pinging but low gears and light car has a big impact on how much compression you can get away with using pump fuel.
@ Hi, The highest we have which used to be 100octane but now can only get 98, but equals around 94/5 in USA. I have 3.5 diff gears weigh around 1750kgs and top loader box.
OEMs (and those of us working on emissions reductions in hot rods) have other tools as well. The decrease in fuel mileage you mentioned can be combated with variable valve timing, EGR, and even Atkinson-Miller via valve timing. The tough part (which is what I’m working on) is variable duration as well, in order to maximize power when using race gas. There are other tools I’m also working on, but these are proprietary (my goals for my 4.6 liter Ford Mustang are 450 hp / 45 mpg on pump gas - not at the same time of course).
@@johngregory4801 3 valve. I chose 3 valve because I’m removing the camshaft (and all the junk in the middle related to the lash adjusters) and replacing it with a pneumatic valve actuating system. 3 valves gives about the same performance as 4 but requires less compressed air for the pneumatic system. The pneumatic actuators are electronically controlled so i have COMPLETE freedom of valve timing specs.
@@ehb403 COOL! Who's it from? I've seen pneumatic valve spring systems before, but not pneumatic actuation for valves. Talk about being able to optimize timing for all revs and all conditions!
@@goldsgarage8236 The engine is from a Mustang, but it’s going in my Ford Fusion…mainly because my wife nixed putting it in the Lincoln MKZ (same car with nicer options and accessories) since it already has a 400 HP engine in it from the factory.
This is a late comment but you also have to consider if the engine has iron heads or aluminum heads. You need more static compression for aluminum heads because the aluminum will act like a big heat sink and wick away all that heat, iron heads will retain more heat and build more pressure. Heat builds pressure, pressure builds power.
Just as dynamic compression, set by the camshaft events greatly influences cranking cyl pressure, a running engine has variables that determining the octane requirements. A high compression race engine with over 14:1 calculated compression ratio with a relatively short duration cam could reliably run on 87 octane gas no problem, if the torque load was kept minimal. This would require a throttle opening to maintain relatively high intake vacuum. In this case, the engine can't develop high combustion pressures/temps associated with detonation. There's a ton of other factors at play, combustion chamber temp and efficiency, total ign. timing requirements, accuracy of maintaining proper fuel distribution and ratio evenly across all engine loads and cyl to cyl, etc... Short answer, in an old school carbureted muscle car era engine, I would agree with your assessment on taking a close look at cranking compression pressure as a good overall indicator of detonation resistance. Unless someone was willing to spend a ton of money to modernize all the development shortcomings due to age of these old engines, and taking the owners dedication and ability to monitor for signs of detonation, I'd say anything over 10:1 would really be pushing it when combined with a typical hot-rod street camshaft.
I have an L72 with fresh .030 over bore and 11:1 forged pistons using stock cast iron heads with oversize exhaust valves. A concours nut and bolt restoration was completed in 2019. The car overheats and I am unable to drive it. I installed a new DeWitt radiator to help with the cooling but to no avail. I then checked compression and found it to be 250 psi all cylinders. The original cam was reground to stock specs during the restoration. The intake is a factory 2 plane (5069) and the pistons are TRW. Everything on this car is new or reconditioned and now has less than 300 miles. I am using straight 104 leaded. The timing is whatever Corvette Specialties set it to. I am using stock exhaust manifolds w/2 1/2" exhaust pipes and stock 355 rear end. The car is very difficult to take off in and between that and the overheating is not much fun to drive. Do you think that the compression is the cause for the high temperature? Any advice would b much appreciated. Thank you.
Thanks for the question David. According to the GM manual, the cranking pressure for an L72 425HP 427 is 150PSI, even though it was 11.0:1 Static CR. I suggest we start by recalculating or verifying your static CR. The bore is 4.25 and the stroke is 3.76. You need to know your combustion chamber volume, head gasket thickness and piston dome volume. If any of those things were changed during the rebuild, machining the heads or block surfaces, thinner head gasket etc, they may have increased your static CR. To determine your dynamic CR and cranking pressure you will also need the connecting rod length, 6.135" and the IVCP (Intake valve closing point) of your camshaft. Unless you already know this or the engine is accessible to degree the cam, it is unlikely you will have this information. Since your cranking compression is so far off, and the engine also does not run well, I am suspicious that something is wrong with the assembly. For example of the timing chain/gears were aligned incorrectly, (camshaft advanced a link or two) , that would close your intake valve even sooner, trapping more compression. Similarly if there were mistakes in the camshaft regrinding, same result. This would be an interesting project. Do you have the cam specifications? degreeing the cam would determine if either of these things were true. That would mean determining the centerline of the intake valve and then closing point. IVCP I would start with degreeing the cam. The engine has to be out of the car to do this. Let me know if this is helpful. AG
Looking at my response from last night. Two other possible causes of your condition could be ignition timing or a vacuum leak. Your timing should be about 36 degrees total at 3000 RPM with the vacuum advance disconnected. You should be using vacuum advance connected to manifold vacuum below the throttle plates. (not port vacuum) Also check for vacuum leaks. There is a large vacuum port at the back of your carburetor below the float bowl, hard to see it and I have seen this left open before. That would cause extreme lean condition, overheating and terrible running. This still doesn't explain 250 PSI which is too much. AG
Check your thermostat in boiling water to make sure it opens when it should I found most of them don't work nowadays or when they should at least The most accurate ones I found are the Edelbrock thermostats
We run over 16 to 1 on Pump Gas with Cranking comp of 220 we also don't go near Peak TQ or load it going down the road and chance to Race gas at the tracks. There is lot of work goes into being able to do this but it can be done.
@@goldsgarage8236 it’s a 712 inch all billet semi Hemi from Todd Goodwin it makes over 1300 hp. We Run Sick Week and Hot Rods Drsg Week. N/A it’s going 7.71 at 174 1.11 60 ft. Not to many people understand pumping losses from lift and duration, ramp design effects on it. Good information overall
Direct injection is the key to running on pump gas with high CR. My 2023 F-150’s 5.0L V8 engine is running a 12:1 compression from the factory and can run 87 octane up through E-85. On 91 octane the crank ratings are 400 HP/410 LB FT from the factory. On E-85 it’s 420 HP/430 LB FT (also from showroom floor). It actually uses dual PFDI injection (One DI and one PI injector per cylinder.
Yep this is correct and if you if you follow his 61 versus the 81 after bottom dead center that's where he gets it back on the right now yep and I believe that will and his destination is going to make it to the definition for gas cuz that's what we're going to do run pump gas and see if I can do it with 13 to 1 or 3:27
FYI the Mercedes M276 DE35 is a factory 12.2:1 compression ratio. I run mine on E15-88 , pump gas is no problem with high compression if the motor is built correctly to reduce hot spots in the combustion chamber that can trigger pre-ignition/detonation
225psi cranking compression, and pump fuel for my street daily driver 379ci standard 4" bore 4 bolt main small block combo. Have run as high as 250psi with a Holden 6 on pump fuel. The other street strip daily driver combo of mine is a 327 2 bolt main 14:1 compression combo
@@dennisrobinson8008 How many times do you ask for forgiveness at night knowing you have 14:1 on a 2 bolt? Just kidding but still, goes all against the 1970's tradition of dissing the 2 bolt.
VERY WELL PRESENTED. ALSO LOBE SEPERATION ANGLE. L88 WAS 114. TIGHTER LIKE MOST COMP CAM STREET CAMS ON 110 MAKE MORE CYLNDER PRESSURE WHICH EQUEALS MORE POWER. ALUMINUM HEADS ALOW 1 POINT MORE COMPRESSION ON SAME OCTANE..180 TO 200 PSI ON A PERFORMANCE STREET MOTOR RUNS NICE. BUT NOT SO MUCH FOR TOWING BECAUSE OF HEAT GENERATED LONG TERM
I think You should be able to run off of 87 with this compression ratio! Here are the reason why: 1. Rod ration is a factor; the higher the better; 2. Combustion chamber design/efficiency; 3. Piston design/quench; 4. Constant cooling temp and adequate cooling system/components; 5. Good fuel quality/low ethanol content/low moisture; 6. Precision fuel metering/A F Ratio; 7. Vehicle weight; 8. Gearing and Transmission; 9. Appropriate Cam selection/Timing; 10. Properly machined and set-up Cast Iron head; 11. Correct Aluminum intake manifold! I also think a good oil and standard volume oil pump would be the right choice for a street application. 12. Properly sized exhaust system should complete the total package..
What is not considered is why the intake closing is delayed. CCP does not consider actual running engine at higher engine speeds. The late closing allows inertial to better fill the cylinders so even though the engine degrees of duration with a closed valve is reduced on compression the cylinder has packed in a larger mode dense charge. The bleed off that is seen at low speeds and cranking is now negated. Dynamic cylinder fill takes over and the demand for higher octane prevails.
I worked in a building that one business unit did QC for refineries and stored aviation samples from plane crashes for testing. One thing today is its not really fair to call fuel octane still, it's blends of multiple carbon chains, many lower than octane, i remember as a kid my dad burning bush piles with purple and when the match was in the air you were heading the opposite direction and the whup went through you, today sometimes you can't barely get a fire to lite
My static is 10.2:1 ish. I have a comp XE266HR12. Warm cranking compression is between 162-165 on all holes at 5200’ elevation above sea level. Adjusted to sea level 192 cranking compression. 4000+ lb manual Bronco. Runs great on 91 @ 32 degrees
I had a 64 Chevy II that had the “140” (last 3 numbers) cam and 12.6:1 compression ratio according to the guy that owned the car before me. The car had a 4 speed and 4:56 gears. It ran on the street fine but would really wake up at 5,000 +!
Thank you for your wisdom....I've watch David Vizard and many others...I want to switch to BBC after a life time of being a 327 fan. I appreciate the fact that you guys are willing to share your knowledge...my next project is a 1968 El Camino with 4 speed 373 gears and red line of 6,000 RPM. This is a street car that i want to be strong as i can get with a 454 bored to 60 over or maybe a 496 stroker with iron heads....any advise would be greatly appreciated. Keep up the good work.
Thanks Michael. I recently built a 427 that is very similar to the ZZ427 GM Crate motor. There are videos about it and another one that I built on my channel. I will be installing this engine in a 1966 El Camino in two weeks or so. I will be making videos about the conversion from a SM. Watch for it.
Hal's dad gave him a 67 SS El Camino with a 396 4 speed GM 21 muncie . It was black and was amazing . the boboso traded it for a 1969 Triump 650 motorcycle . We all told him he f up .
We ran our 482 big block Chevrolet with 12.5:1 on 91, for YEARS in a boat. Kept the timing at about 36 never had an issue. My current engine with 11.8:1 runs great on 91 with 34 degrees, been in the car since 2008 with EFI controlling the fuel.
i was wondering why you don't use Brass freeze plugs, i enjoy listening to your video's as we are never to old to learn what you have to say even tho, I am 80 yrs old and still enjoy hot rods. I have a running project 1940 ford cp. with a 327 with a tir power carbs setup and a new 5spd TKX tranny with a dodge 8.3/4' & it's has a 4.10 rear axle ratio. I'm using 80's 350 truck heads with the angle spark plugs to lower the compression to about 130 psi so, I run 87 octane pump gas. .
Wow, 80 and still digging, I hope to do the same. That will be a cool rod with the tri power 327. Actually i usually do use brass frost plugs and i am installing them on my current build for Will Casey. I just happened to have the steel (galvanized) ones . Steel plugs will outlast us but brass looks cooler for sure. AG
good info probably should also mention how cams with large overlap will effect cranking compression. Mine makes only around 90 psi cranking pressure but has a large overlap and duration. Effectively pushing combustion out intake port at low speed. The compression ratios is around 9.5:1 engine is turbo charged and makes 700 hp from 2.4 liters at 8500 rpm.
Overlap effects idle quality. Intake closing effects cranking pressure. More overlap will actually increase low to midrange cylinder filling and that is why dirt track guys run a 107 or 106 lsa cam instead of 110 or 112. The 106 - 107 will pull a lot harder off the corners but the idle quality will be horrible. If you are pulling up past 7k rpm the higher lsa 110-112 would probably be better because of better higher rpm cylinder filling.
Thanks Jim. That depends on a lot of things. Generally speaking 95 octane should be safe for 10:1 CR for cast heads and 10.5:1 for aluminum heads, however camshaft timing and even the pounds of car / ratio to cubic inch and gear ratio is a factor. My rule of thumb is 160-180PSI cranking pressure which verifies your DCR. Hope this helps. AG
great video, the thing that NO one ever talks about is how many BUMPS on the comp gauge is required to get the needle to 150PSI? Hydraulic lifters give mushy valve action when cold so thats why we test at operation temps. Ive done 100s of comp tests at GM on thier dynos in australia and the SLOWEST comp needle movement was from the LS series of engines, they required 8 comp bumps to get to the desired 150PSI with a 10.4:1 engine! But when we took out the corvette cam & installed a 5.3 truck cam the comp was now 165psi & it only took 4 bumps on the gauge! testing on the truck cam bought peak torque and horsepower down the RPM line about 1000rpm. My boat has a 351c with 302c heads & laid back chambers to give a measured 10.2:1 comp, with a 218 cam. comp gauge reads 165psi in 2 bumps on the gauge and it just likes 95 ron fuel ( your equivelent 91 octane)... I really enjoyed your video, keep up the good work.
Thanks Wayne from Australia. Did you know, the number 1 city in terms of clicks on my site is Milbourn Australia and many other cities in Australia are right up there so thank you for the great support. I think the Wallace Racing guideline is 7 bumps but for the reasons you mentioned I think you should keep going until the pressure reading stops going up. Usually that is about 4 bumps. 91 fuel should handle 165psi easily. Hope this helps. AG
you mean MELBOURNE. Thats where im from. We have some smart people in the aftermarket head and manifold design. CHI heads ,AUSSIESPEED manifolds YELLATERRA heads& valve train SCOTT COOK cleveland heads , to name just a few.@@goldsgarage8236
I worked at a Chevy dealer in the 1960s, I did alot of tune ups, and we always performed a compression test. most cars fell into that 150 psi range. I worked on alot of Corvettes and some of the HP engines would push the psi well over 200 some as high as 250
Very interesting Monty. In the 1968 GM manual specifications, the highest cranking pressure for any engine is 160PSI, except the Z28 is 190PSI. Do you think carbon build up could be a factor?, or where these engines modified? Thanks for your comment, we are learning from your experience. AG
12.5:1 SCR on pump gas? Absolutely! Even with steel rims. Yep! Seen it done many times actually. Definitely premium gas, 93 octane from my experience. Can't comment about anything lower, but I have heard it can. I remember a time I believed in some of the stereotypes, and at the time they seemed correct because it typically came from people who seem to know what they were talking about, however I kept going back to the first time I seen very high compression with steel heads on pump gas. And that would be the engine my stepfather built. He was running 12.5 to 1 static compression ratio, Steelheads and ran 93 in it. No problems. Regardless this is when I was first starting out and learning everything. Buy my mid-teens my brother and I were already doing engine swaps in manual transmission conversions etc etc, and we were building what was considered high performance engines at the time, in the early 90s 400 or 500 horsepower was extreme horsepower, lol! Anyways what has seen my stepfather and others do always nagged at me when I heard the so-called experts on compression Now many many years later, when forced induction is in its prime, I continue to hear misconceptions about compression. People have this idea that when you use the force induction you have to go with extremely low compression which is not accurate. I am running 11.0:1 SCR with twin turbos. My brother 10.5:1 with a turbo. On premium pump gas. Don't get me wrong, we have Holley EFI systems which help with tuning and getting the best out of everything, however really is more based on putting the correct components together. Too many people look at the individual parts and or maybe a couple of them together. For instance you may look at the camshaft with cylinder heads or something like that when in fact it is everything all together and even as this guy has stated which is very important, is the intended use. Many people don't consider the load, factors that play such a big role in what you are doing
I think you can run 87 with a 12.5 compression motor if the cam has plenty of overlap, reduced spark timing, and running only at lower RPMs with light throttle. Didn’t Crower cams offer cams to run high compression engines on pump gas?
Thx for putting up such Rare & Helpful info on a very hot topic for us hp factory iron guys....It really Is a comparison & engine Octane fueling Dilemma because the popular 0.050" lifter spec cams & the typical solid lifter 0.020" cam card timing data Is Way Different from the factory 0.006" lift SAE valve timing specs......Even using Long ramp Bleedoff cam timing, Chevy Did affix Octane Warning stickers to factory Iron head, L88 engine that Minimum rated Octane was Ron 103 & Mon 95, with Mon rated fuel Preferred.....Why would Chevy bother with that warning If Lower Octane Was Not a Problem ?? ....Looks like Chevy Didn't put much faith in the DCR effect ??.....With U.S. Pump gas 92 AKI (R+M)/2 rated at 88 MON, how is that supposed to work with factory Stock shim head gasket & Internals ?? ......Around engine Max Torque Rpm range, the cylinder Does fill Beyond the IVC point, nearly to Full BDC cylinder capacity & Nullifies the Lower calculated Dynamic CR is Probably why.....Maybe the clever use of "Squish" optimized Aluminium heads & smart ECU Detonation sensor designed ignition system can let the Stock engines run flat out Again on the current pump gas Octane problem.......
Well, it's quite possible it could. I'm at 3500 ft elevation, so a hot street engine in most cases needed 11.5 static compression and depending on the cams intake closing, it could definitely run great on pump. Good cylinder head chambers, and proper quench are also important. It's also worth mentioning that today's Ethanol blended fuels have a different Stoic ratio, it's not 14.7 to 1, it's 14.01 to 1, so a proper tune will need to be richer that most people think. And it won't require alot of timing because the fuel burns quicker. If you tune a high compression engine as If it was forced induction, it will be fine....
Thanks for the info Duane. We are 753 feet above sea level so that s not an issue here. Thanks for the info about stoic ratio. We tune for results on the dyno, usually about 13:1
@duanedahl8856 point is correct regarding the difference in air/fuel mixtures between straight gas and gasohol. Inherently today's engines don't make any less power on modern, alcohol-blended fuels versus gasoline from the "old days"; they just burn more of the new stuff to do it. In fact, modern fuels with higher alcohol content can actually help to enable greater power because the charge cooling affect of the alcohol permits more dynamic compression and/or timing (i.e., higher cylinder pressures without detonation).
The issue with cranking compression is the rpm the engine cranks at. Street engines with higher tension rings tend to turn over slower than a comparable engine with low drag rings. Higher compression can cause a slower cranking RPM if the plugs are left in the other cylinders. I typically remove all the plugs. This gives a better picture of the condition on the cylinder being tested. Sizing cams is an art. Bore to stroke ratio does come into play and it's opposite of what I thought it would be. The longer stroke engines appear to be more fickle with duration than shorter stroke engines. This is for racing applications and may not matter for street applications.
Those are all good points Brad. It is good practice to remove all the plugs and have good cranking speed when taking a compression test. Thanks for your input. AG
Can you explain the benefits of hi compression motors? Can you use less fuel and more air? How are direct injection gas motors making safe hi compression motors on reg fuel ?
Thanks for the question Taras. That is a great suggestion, you just gave me an idea for future video on this subject. Watch for it and let me know if I answered your question. AG
11:7:1 guy told me colder plug no issues They changed cam during bottom end upgrade it took way too much vacum idles fine worried about detonations. Vacum canister or pump he does not know where my original cam is. I wouldnt buy a flat tappet now with issues. Old was 1600 to 7k rpms new is 3k through 7k sounds great taking it cross country
I'd push 11.5 1 with fast swirl aluminum heads and the right dur cam. The higher a cam lobe lifts the valve off the seat it does hold the valve open a little longer. But few cams are streetable past using a 285 dur cam.
I have to chuckle, watched my first video of yours and asked a question to then refresh my computer to land on my second video of yours that looks like its going to answer my question lol.
12.5:1 on pump gas, is doable depending on what ignition timing one is running, depending on altitude, and how hot and humid the place is. Also how hard you're running the motor.
So I see this conversation come up quite a bit with regards to making power on Coyote applications where people are trying to make 750-800 plus hp on boosted setups on pump 93. Can it be done? Yes, but they don’t like it when you tell them that it isn’t a great idea and it likely won’t last very long without adding octane additives or switching to E85 or race fuel.
I once ran a 327 sbc with 10.5:1 compression with ported camel back heads, a pretty hot cam, headers, a Holley 600 (tuned) with a Mallory Unilite ignition. Ran very well for several years on 91 octane gas (NO pinging). Good aluminum heads might be better for more compression. I was probably putting out around 375-400 hp. Only reason I was "slow" was because I had a 3.42 open rear end in a 1972 Camaro. If I had a 3:73 posi, I would have been MUCH faster, especially with really good tires.
Thanks Hans. Gearing helps. I installed a 4.88:1 gear in my Camaro in 1969 and it was still there when i bought it back. Lot's of fun on the street. Sounds like you built a nice SBC. AG
Would you know perhaps what would be a better camshaft than factory on the vw 2 litre air cooled kombi, I think torque would be more advantageous, unless you think original cam is still a good choice. Thanks buddy 😊
Thanks for your question Harry but I don't have much experience with this engine and don't know enough about the application. Consider the end use, daily use vs. race, weight ratio, lb./cu. in. gear ratio, type of transmission, RPM range where you will need the performance etc. Hope this helps a bit anyway and thanks for watching. AG
First calculate your static CR with the Summit on line calculator, just google it. Then google Dynamic CR, a Wallace Dynamic calculator should come up. Just fill in the required information and you will get your DCR and cranking pressure. Hope this helps. AG
It does. Thank you. I was getting a very low pressure when using a different calculator on Wallace. The dynamic compression ratio calculator on Wallace is the correct one to use as you say. That calculation also includes the dynamic pressure calculation along with the dynamic compression ratio. Thank you sir for clearing that up.
Thank you for the video. I'm learning all I can about this stuff. I'm about to take a healthy 6.0 and put a cam, springs, lifters, etc in it. I like that you are conservative. So, I have two questions. First, this LQ4 engine comes with 317 heads. The engine has a 9.4 to 1 ratio stock. I also have 706 heads from a 5.3. Everyone is telling me to use those. They would boost my compression to around 10.5 to 1. Do you think I would still run fine on 87 octane? Second, what cam would you run for daily driver, a bit more power, and mileage?
Thanks for the question Dylan. I am not as well informed on LS engines, however if you are building high compression, I would use the best pump fuel you can get. As for cams, the LS engines doe not need as much duration as the GEN 1 engines partly because they are all roller and can accelerate the valve faster on the ramp. Check the IVCP and calculate your DC and cranking pressure before you decide. The final result depends on many factors, the power/weight ratio of your car, gear ratios etc. Hope this helps. AG
I had a 427/ L88 and was out one night and needed gas to get home and only could get my hands on 87 octane I had to back off the timing big time to get home without pinging every time I touched the gas.
So my stroker 427 sbc has a cranking compression of 210 psi. The builder said it has a dynamic comp of 11.1 to 1 he recomended i run a minimum of 100 octane i so so by adding an octaine addative. To no ethanol 91. Cam has 272 duration at 0. And a 109lsa on exhaust 112 on intake. Is he out of line or could i run 91 octane without ehanol. I believe that fuel is non oxygenated as well.
Great question Boss. Let me try to explain. Air and fuel mixture has mass and so it also has inertia. The inertia is proportional to speed (RPM) of the engine. At low RPM the air fuel mixture has very little inertia so after BDC the piston is able to push it back into the intake plenum until the intake valve closes, usually about 40-65 degrees ABDC. This reduces dynamic compression as nothing is compressed until the intake valve closes. This is called reversion and is what causes the rough idle and poor low RPM performance with long duration cams. At high RPM however, the mixture is entering the plenum at a high velocity and actually compresses against the closed intake valve. At the overlap TDC when the intake is opening and the exhaust is closing, that inertia purges out the exhaust gases until the exhaust valve closes, then rams into the cylinder until the intake valve closes, almost a supercharged condition. A long duration cam has more overlap at TDC which helps high RPM performance, and a late closing point for the intake valve which reduces detonation. If you have lots of (static) compression, you need a high duration cam and vice versa. I hope this helps, please let me know. AG
@@goldsgarage8236so if you have a cam with shorter duration with a smooth idle i think I'm saying that correctly you would need higher octane fuel ? Thanks in advance .
150psig @ sea level is 10:1 compression ratio, and the higher you go the worse that is Direct injection & advanced engine electronics is how my turbo 4 runs an OEM 13:1CR on 87 octane gas in Buffalo NY
Good question Topgun. I don't think it would make much difference on anything aluminum but a sharp edge or rough surface on cast iron could potentially glow and cause pre-ignition. AG
i think of it this way. The Pontiac i am building now has about 10.4:1CR with steel heads. The dynamic CR and cranking pressure are more important. It will have under 180PSI cranking pressure. You can calculate all this using on line calculators, Summit for CR, Wallace for DCR. Your camshaft IVCP ABDC is a big factor in this calculation. If you aim for these levels use the best pump fuel you can find, manage your ignition timing, keep operating temperatures under control
Good point Scorpion. VE at high RPM will increase peak pressure and MEP, which is the average cylinder pressure during the complete down stroke. Typical MEP would be 10-15 times atmospheric pressure. AG
Great Video!! 22r (2.4 liter solid cam) street driven Weber 32/36, dual plane, stage 2 cnc’d heads with +1mm valves all port matched, ~9.8:1 , mid length header with 2.25” exhaust. Currently have a Crower (EFI stage 2) 216/220 @ .050”, advertised 270/276 with 430/430 lift and 114* LSA, which was obviously not the LSA I thought I needed, but I like the specs of the rest of the cam! Crower has the stage 1 Carb version (same specs as efi stage 2) with a 108* LSA, which I currently plan to buy to hopefully run 87 and get 25+ mpg city (with 3.73 gears eventually, 3.07 now). Your time is appreciated, and your thoughts greatly appreciated. Without dynamic compression measured, is ~10:1 on 87 octane likely, or is my head still in the clouds? Rare to find someone that tailors to street driven vehicles, so I’ll be checking out your other videos for tricks before I pull my motor back out. Currently have 9:1 pistons with 114* lsa cam and bought KB’s 9.7:1 hypereutectic and shopping for a better cam. If it won’t run well enough to stick with 87, it won’t stop me, but don’t want to ‘tune myself to death’ trying to accomplish the impossible if I just need another octane point. They have a stage 2 cam with 226/236, 286/290, .429/.443 with 108* lsa (which might be too big for low end desires and possibly too much dynamic compression to risk detonation but recommended upgrades of engine requirements align but they project a 3,000-7,000 power band versus 2,200-6200 for the stage 1) or another option is having them custom grind one similar to these specs, maybe more exhaust lift and/or tighter LSA. Thanks again for the video!
@@johnsheetz6639 every 22r owner that has spent a lot of money will tell you they won’t make much hp but the torque is pretty decent. I’m $3,000+ invested in the motor and with manual steering and electric fan (less parasitic loss than clutch fan) and 9:1, I maybe freed up 115-125 hp to the wheels. It’s not a very satisfying engine to sink money into but can expect to see 200,000 miles, it appears. They are described as tractor engines and I agree, so depending on what you want to use it for, you’re probably better off with any other engine in the world for hp unless you boost it… and even then, there’s probably a better alternative.
@@johnsheetz6639 as for the 20r head, they have a hemispherical combustion chamber and a straighter path for air to flow in the ports for better velocity, so depending on your build, they could be a bolt on bunch of fun. They are also rare to find, which drives the price up.
@@Dube7666 that's what I heard before and the Jeep 4 L is one that's kind of the same. They both remain two of my favorite bulletproof engines though. They are engineering perfection for getting you there and back!😎
@@johnsheetz6639 I always like the jeep cherokee and thought a low rev turbo with a straight 6 would have a lot of torque… but the Jeep emblem cost on every part adds up before it even begins.
Interesting Camshaft comparison at video 13:41....Are Both Camshafts Actually Measured using Exactly the Same measuring Method or is Any of the IVC° data Estimated or Equivalent Computed as this is 1 OEM Solid compared to Aftermarket Hydraulic cam ? ...... Exactly did Chevy Measure their Solid lifter cam IVC° & Intake Duration ? .....I don't think 0.050" or 0.020" at Lifter Check Height was used.....Anyone know for sure ??
Good question Tom. I calculated the effective IVC based on the other known factors. It would be impossible to measure with a degree wheel because of the soft ramps. Pretty sure the .050" measurement was not common then. We just degreed to the centerline. Thanks for contributing. AG
Thx so much for responding....I'm really Interested in this topic as I have a Mopar build going on with a solid FT Cam & concerned about same Expected octane issues....My error on the L79 OEM Solid lifter spec, I know it's Hydraulic also....Why not Compare both cams Measuring at SAE 0.006" Lifter Check height (using a solid lifter) Similar to what Factory spec was for the DCR calculator input value ? .....I'm real interested in what's Actually happening at between 0.006" & 0.050" valve lift & think the 0.006" lift point would More validate the OEM extended lobe ramp effect issue on Actual IVC° point.....Thx again,...Tom..
Your video was excellent! I am in the process of selecting an engine builder to build a new 421ci small block Chevrolet using a Dart SHP block with a 6-71 blower and AFR195cc heads with a 75CC combustion chamber. One of the items we are discussion about is camshaft profile and piston dish selection. He is proposing a 36cc dish piston (off the shelf), and a 255/239 .600/.580 114LSA hydraulic roller camshaft. What do you think about this combination?
Thanks for the question 331. Looks like a nice very high end build with all good parts. You might calculate your static and dynamic CR and cranking pressure to see if it works with the blower. Is this a pump gas or race fuel engine? What % boost are you planning with the blower? Your blower will increase the dynamic compression pressure and MEP, (Mean effective Pressure) That is how it makes power but there is a limit before the risk of detonation on pump gas. Bill Little, if you are watching, can you comment please as you have experience with blowers? AG
@@goldsgarage8236 thank you very much for the response. This is a pump gas street driven vehicle, with between 7-10lbs of boost (to be tweaked on the dyno with the pulley setup).
Good point Alonzo. Here is how it works. The valve timing bleeds off compression at low RPM only. The fuel air mixture has mass. At high RPM the mixture is travelling at 200-400 RPM so it also has inertia. This helps to fill the cylinder on the compression stroke and purge the mixture on the overlap cycle. Dynamically you will have lots of compression. Engines are more less vulnerable to detonation at high speed because the flame travel takes time and the piston is moving rapidly. Hope this helps. AG
Alonzo, I just caught a mistake in the comment above, the fuel air mixture is travelling at 200-400 MPH, not 200-400 RPM. Engines are LESS vulnerable to detonation at high RPM. AG
Good question John. Cranking pressure is simply compression pressure that you can measure with an inexpensive compression gage that you can buy from any auto parts store. it screws into the spark plug hole, (disable the ignition) then crank the engine over a few revolutions or until it stops climbing. For a street engine on pump gas I like to see 160-180PSI (pounds per square inch). Compression makes power but if you have too much you can cause detonation which can damage the engine. To calculate it on a build, first determine the static CR. You can use the Summit on line Calculator. You need to know your bore and stroke, combustion chamber volume, piston dome volume, deck height and head gasket thickness. For street, aim for 10:1 for steel heads and 10.5:1 for aluminum heads. Then you can use the Wallace Dynamic Compression On Line Calculator. Now you also need to know the connecting rod length and the IVCP (Intake Valve Closing Point) of your camshaft. The result will be your dynamic CR and cranking pressure. Hope this helps. Let me know. AG
Thanks Bryan. Generally bigger cams don't make a lot more torque, they just raise the RPM where that torque is made. HP= torque x RPM/5252. So if you use a cam that produces torque at higher RPM, you need gearing that raises your RPM and takes advantage of it. So as the operating range of the cam increases, the gear ratio should increase proportionately. Hope this helps. AG
Hi, just a quick question. My 406 pontiac has 190 psi on 6 out of 8 cylinders and 210/215 on the other 2. Wet compression test yields another +30 to + 40 psi ranging from 220-250. i have an excel file of exact measurements I'd like to email for a 2nd opinion but just curious if what I've written leads you to believe the rings are probably toast. Dynamic compression test next while it runs coming up. Leak down % #'s are from from 8% to 17%. TY
@@ubethejudge69 I’m travelling right now so responding from my phone. Don’t over react. Your leak down numbers are not bad so I think the rings are ok. Higher compression in two cylinders could be carbon, or in accurate reading. Run it and check again. Even 190 is high for the street. How does the engine run?
@@goldsgarage8236 Appreciate reply while travelling. I didn't think of carbon - good point. I have some pics of pistons from scope - maybe some seafoam would clear that up. I just want to rule out all test's before giving up on fixing whatever has been missed. troubleshooting performance issue for last 15 + years. Engine runs fine , no valve float. Just the power has never been restored. No shop or anyone would know anything is wrong with this engine. Even though a shop tore it right down 15+ years ago and put it back together from scratch - it has never ran how it did when i first bought this car. - no mechanic/ engine builder / shop has been able to truly say this reason a) or b) . They say ... let me build you another engine. dynamic compression coming soon
Are you sure you have the tune correct? With 190psi, you have to be careful about timing and detonation. How about camshaft or camshaft timing? What are the cam specs? AG
@@goldsgarage8236 Thanks again AG! 02 sensor installed while back, good idle and WOT safe #'s, plugs - light tan . Never heard detonation since owning it (1992). Realize doesn't mean it isn't happening. Initial timing 18/Mechanical 18. I do not know camshaft initial installed degree measurements (1992) as car was bought site unseen. A shop rebuilt it in 2000 when that cam went flat, same cam chosen-284h-crane degreed the 230/230 .480/.480 LSA 112 on ICL 107. Just a list of things changed last 20 years - distributors/carb's/springs/rockers/torque converter/ intake's. Dynamic idle #'s 110-130 psi / Snap 165-180 psi. Any other tests you might have let me know . I really don't see anything wrong with these #'s , I don't see anything happening with the heads to warrant them being pulled to inspect. It looks like rings are good? My only clue was cranking compression prior to rebuild was 165 , they shaved the heads .10 thou and cam was far advanced more than usual 4 degrees. I can only think of bringing cam to 112 ICL straight up or even 114 - 2+ retarded ? Maybe that magically restores the top end rush seat of pants back. Incidentally the pop up pistons in this engine have swirl marks on the top which could be casting swirls or hidden detonation? How would i even test that theory if somehow the pistons were the culprit.
@@goldsgarage8236 Oh hey, just wanted to circle back. Hope you had great trip. Thanks again for your help. I don't think there is a problem health wise engine as it relates to rings / heads. I think you would agree. From the internet. My only course of action is to run cam straight up with no advance and see what it does.
In the USA octane in the 60's I believe was motor octane and today it is an average of motor and research octane number (R+M/2). RON is tested on a special engine that can vary the compression ratio at idle and MON is tested on a special variable compression engine at higher loads and speeds. I think that I have read that many other countries at least once upon a time used only the MON rating which could be a different number than we use in the USA. I haven't thought about it in years so I don't know if that is still true since things are always changing. I'm not sure but I think race fuel in the USA is MON only.
Generally speaking, and negating the hundreds of other factors that effect engine power, will more timing with higher octane usually have more power ? As an example, if we had a typical 500 HP BBC street beast running great on 93 octane, with say a 10:1 CR, and 30* total timing, gain more power simply by changing to a 103 octane and bumping timing to say 36* ?
Thank you, great video. I am a new subscriber, and of course I have some questions. I think you are in Canada so maybe fuels are different than US but I was born in 1969 in Connecticut. Until around 1990 we had 87 unleaded, 93 unleaded and 89 leaded. After 1990 no more leaded but it remained 89 octane. We currently still have those three choices of unleaded. You talked about 1968 with high compression Motors. I guess there was no unleaded yet but regular was 87 octane leaded and what was the octane of the high-test leaded? And was there two or three choices of pump gas octane? That 100 octane fuel you mentioned, was that race fuel or pump gas? And today I see we're up to 12 and a half 1 compression again but with 87 octane and I guess that's due to direct injection?
Thanks for the question Not Me. Sunoco had multiple choices, the highest was 260 with 100 octane right at the pump, not exactly sure of the other blends but I assume it was down to 87 or so. You are correct about direct injection, as the piston is only compressing air until just before ignition. Let me know if I answered your question and thanks for supporting my channel. AG
@@goldsgarage8236 well done, thanks for the answer. Yes I was confused because it seems like the name of the gas is 260 but the octane is 100. That was just slightly before my time so I missed out on that. But it must have been great to get 100 octane leaded fuel for pennies a gallon. Thanks Daryl Florida
I would like some advice on cam selection. 5000 lb 4x4, ford 400cid engine, 10.8:1 static compression ratio, ELEVATION 6000 to 8000 feet, C6 auto transmission, 3.50 gears with 34" tires, TFS heads. Elevation totally messes up my cranking compression ratios. I would like a 170 to 180 psi cranking pressure at my elevation. What cam specifications should I be looking at? RPM range 2000 to 4500.
My main issue is elevation. I would like to have a camshaft that will make pressure at 7000 ft as if it were at sea level. 160 psi at sea level is only 128 psi up here. Off the shelf RV cams do not factor in elevations like I deal with.
Bleeding off is only effective at low RPM when the engine is vulnerable to detonation. At high RPM, the mass and intertia of the FA mixture fills the chamber. AG
Hearing you talk about that GM "151" cam made me smile, It was my number 1 choice for my pump gas street engines in the early 70`s. In the early 90`s I used the 292H Comp cams for that lumpy idle the guys liked and it run strong in a 350. One of the old guys I worked with when I was a pup told me to assemble the long block on the stand put a starter on it and starting at straight up take a compression check then advance the cam and take another compresion check and stop when you got the highest reading, it worked surprizsngly well. Them old boys know there stuff.
Thanks for sharing your knowledge and experience Ed. That is a good method. AG
Mr. David vizard is great! There’s only like 4 guys that I know of that can explain it really well!
My respects to all of you’
Nice compliment Roger. Thanks so much. AG
I wish one of them could not take 20 mins to say what should take 2 mins.
I spent my whole life around drag racing and build blown fuel engines for a living. This is really really good content. Touching on things most enthusiasts don’t understand 🤘🏽
Thanks Groom. Nice compliment coming from someone with your credentials. AG
It never occurred to me that the cam would directly affect compression, but thinking about it it makes total sense. Many years ago (1985), I had a 1972 Oldsmobile with a 455 that appeared to be stock. It had plenty of torque and was fairly good on gas. I always ran Sunoco Ultra which at the time was 93 octane and it ran great on it. I did cranking compression test on it and got between 185 and 205 psi. It also had nice idle and the stock GA heads typical for ‘72 455s. Thanks for the great presentation, you got me thinking.
Thanks for the info Steve. We are always learning. Your compression pressure explains your good torque and mileage. AG
I ran well over 13:1 on pump gas. I did not build this engine to run on pump gas. I purchased a used 406 short block and was going to put my top end on it which consisted of a set of AFR210's and a port matched Victor Jr. with a Race Demon 835. The 406 turned out to be junk and I already had a camshaft made for it for nitrous. The compression of this 357 smallblock was well over 13:1. The pistons were Ross 91461 with a 15.2cc dome, it was zero decked, the chamber size of the heads was 66cc and the head gasket was 0.040" thick. The cam was 268/274 @ 0.050" with a 108ICL, 112LSA and 630" lift. I ran it on the street and raced it on the track with nitrous. After running it for a while I did a cold compression check and it came in at 195-205. This was lower than my previous 355 so I ran it on 91 octane pump gas while on the street and race gas when I took it to the track. Race weight was 3,420 and it ran 11.20's at 120 on the motor and Ten teens at 132 on a 175 shot.
Thanks Steve for sharing your knowledge and experience. Confirmation for me. AG
I remember reading an article in a Chevy Hi Performance magazine where some automotive school was tasked with trying to make 700 ft lbs of torque on 87 octane. They ALMOST succeeded except for a mechanical problem with a spiroloc missing. The build was a 502 BBC with hypereutectic pistons having a CR of 12.5:1 and the engine having a special flat tappet grind and including Feuling aluminum peanut port heads with small chambers. I believe they used a Holley street ram efi setup along with an aluminum radiator filled with Evans NPG coolant. The motor ran fine until the wrist pin on one cylinder worked its way into the side of the cylinder. I recall being amazed that such a high CR could be utilized on 87 octane. I wish these greedy petroleum companies would produce just one street octane of like 95 or thereabouts. Europe only does one octane to my understanding. Thanks for a great video.
Thanks Racer, that is a stretch for sure. AG
It is a Chevy engine, my respects; I’m mopar small block, but you explain it so simple I respect you, and every one no matter what brand!!!
The knowledge you have some humans don’t understand that did not grow on roses over a few nights!!!
Thank you so much for this serious and true information!!
Thanks again Roger. We will have a 340 Mopar on the stand as soon as I get these Pontiac's done. AG
Its bc all pushrod v8s are very similar... So things I say about an ls or sbc I can say about a Windsor mopar Pontiac Olds to a lesser extent hemis and semis
I don’t think most consumers and average enthusiasts understand that dynamic compression is what matters and yet all you hear about is static. Great video!
Thank you very much Jet. AG
Like yourself, I am a student of David Vizard.
I believe you are spot on with everything that you have stated.
I’m currently building a 400 sbc for a ‘70 Camaro using a lot of David Vizard’s principles.
I thoroughly enjoy your videos, so keep them coming please!
Thanks for all your efforts.👍🏻
Thank you Leo. I will also be building a 406 for my son's circle track car soon. Watch for it. AG
In about 1992 I had a 68 Camaro daily driver with a .30 over 454. I had a .250 domed piston, with a Comp Cams 292 Magnum cam. 244 at 50 and .556 lift. The cranking compression was 225 lbs. on average! I used a stock converter, Turbo 400 trans., and a 4:10 12 bolt rear end. I drove the car on premium fuel at 91 octane. I had to dial back the timing to stop detonation. It wasn't an ideal combo for the street, but it was a beast! The widest tire you can run on a 68 Camaro is 11.5 inches. That's what I ran and the Hoosier Quik Time street tires couldn't hook! It was a ball to drive!
Thanks Rick. That would be a beast for sure. You were definitely pushing the limits of pump gas and also it makes me think i am being conservative with my 180PSI target for street engines. AG
@@goldsgarage8236 Less compression and or more duration on the cam would have been better for a daily driver. The car ran a best of 12:31 at 114 m.p.h. at the track. My best 60 ft. time was a terrible 2:19, because of loss of traction! I never did run it on slicks. In 4 years of street racing I only lost 3 times, and all 3 cars were running either nitrous or blowers! I never lost on the motor only. I was the only true daily driver racing at the time. The Camaro was my only car.
Aiming for the 160 psi cranking compression mark compared to the 180-200 mark depends on a lot of factors. Having extra leeway for detonation resistance is a good thing but it trades off a bit of power. The person that might not have the knowledge to monitor that they might be more prone to engine damage in certain circumstances (like a particularly hot day), should probably have a bit more leeway for their car. The vehicle it's going in plays a roll too; lighter cars with shorter gears are going to be less prone to detonation too. Then there's also the little things in the build; like smoothing out edges in the combustion chamber, quench, piston style etc.
All great information. Great video
Thank Troy, the problem I have with building engines for others is that i have no control over these things once it is off the dyno. i worry about them all. Thanks for your input. AG
@@goldsgarage8236can 93 be ran in a 12:9:1 compression 408
Thanks for throwing this information together in such a concise video. I've always known a cam, or cams have direct influence on dynamic compression, but the point you brought up about how quickly the cam acts vs the duration is interesting. I like how you broke it to a ratio. Simple. Subscribed.
Thanks for commenting and subscribing Danielle. AG
@@goldsgarage8236 You are welcome. Just for the record I identify as a man and my name is Daniel.
Thank you for explaining that so easily and precisely.
As an Automotive machinist, I have tried many different engine combinations with compression ratios, from using frquencied inlet manifolds to boost low and midrange torque, to camshaft s with various duration and split etc etc.
Yes you can run 12:1 + on pump gas and still have a great performance with the benefit of great fuel mileage to boot.
good points, thanks for your comment Dean. AG
I’ve watched a few of your videos and I like your approach to things. I don’t always agree, BUT, at the end game I understand your position.
When you dropped the David Vizard bomb, I was like …. ok… we’re on the same plane and path!
I’ve been a Smokey Yunick guy from the mid sixties on. I would bet most us from that time, that he had an influence on us, regardless of the brand.
Really like the channel, well done.
I ended up getting 9 years out of a comp extreme 4x4 cam and Rotella oil. I used the truck for daily driver and off road adventures. At the 9 year mark it started chewing up a lobe on #4 and I had to sell the truck as I had no $ to fix and it was no longer practical for me. Thanks for the no flare no bs info, when you said thats fine we don't have to agree you got me.
Thanks Kris, good info and very nice compliment, appreciate it! AG
The late, great Joe Sherman once said if it pumps under 200psi, it'll run on pump gas. I've ran 13-1 engines on 93 octane on the street, of course I used racing fuel at the track.
You are talking about that cheating bastard, he was great at that for sure.
Thanks for the info.
A man could learn alot from Joe Sherman. Shame he passed away.
Sport bikes commonly run 13+:1 on 93. Of course they have 3D air and fuel tables and huge development budgets.
What changes did you make to your tune to switch between fuels?
My 1998cc Alfa Romeo Spyder (mechanical direct injected) is running 16.5:1 corrected CR on unleaded premium (92 octane 100% gasoline) pump swill and has been for 41 years. It is a Hemi head and it turns 16,000 RPM (peak HP at 12,600 RPM) , but Alfa was building engines that turned 10,000 RPM RELIABLY before WWI! BTW, the Alfa engine has NO valve springs-it uses desdemonic valves with followers (forks) that push open and pull the valves closed. It also has a Magneto Marelli magneto and surface electrode spark plugs that whines like a turbo, driven by the crankshaft. The clock is showing 180,000 Km and it doesn't use any more oil than when new (about a liter between changes, normal by the owner's manual). The four-banger holds 7 liters of oil WITHOUT filter or nearly 9 with filter (big oil cooler built-in).
Very cool Ricky, must sound great at 16,000RPM. Different world than Detroit muscle.
Cool very interesting. I'd like to see the valve train
Big American engines with long strokes cannot reliably turn over about 6000 rpms in somewhat stock configuration. I have no idea what affect extremely high engins revs have on pre-ignition. Most stock engines sold in North America are around 89mm stroke. A $40,000 full custom race engine for circle track use will usually be 6.7 to 7.6 liters, roughly, and they are usually around 100mm in stroke. These engines will run several thousand laps in a year, and they will have acceptable reliability at around 9000 rpm maximum rotation speed.
@@kevinkelley3657 i have a 427 that I run it at 8500 rpms it's a aftermarket Dart aluminum block and 12/1 compression I run M1 methanol and a 98mm forced Inductions turbo point being you can build à reliable engine to turn rpm mine is a small block but that's all that I will give out Openly on here I still race so I'm just saying you can you just have to get the right parts and engine builders I go to tkm there the best in the country.
@@Wardaddy1124 I said in my comment that "custom engines" could turn 9000 rpms reliably in a circle track engine, for one year...........I said that these engines were usually around 100mm in stroke. If you disagree with me, what is your exact argument? I have a VERY good friend who is THE machinist to use in this are........I also understand what aftermarket heads are capable of doing. I am not sure that I understand your argument, but if you have $10k to 15K to spend in parts, you can absolutey build a 9000 rpm chevy based engine that should live for 40 races on a round track under 1/2 mile in length.
If did the calculations correctly (as you say at the end of your video) then, my Comp Cams "Low Shock" cams on the cam card are showing an Advertised duration of 276*/282* and 246*/252* shows 1.12 for the Intake and 1.11 for the Exhaust and according to what is being explained in this video it sounds like my cams have very aggressive ramp speeds which I told them I DID NOT WANT---I specifically told the tech from Comp Cams that I wanted their "Low Shock" cam profile design with easy, smooth, non-aggressive ramps. I guess they didn't get the memo!!! I will send them back! Thank you for your video and detailed explanation.
Thanks Dune, glad you found the information helpful. AG
I agree 180 compression minimum.
I target between 185 to 200.
But that's not written in stone.
All kinds of factors, cast iron heads, aluminum heads.
Cast heads static lower.
Duration @.050, gears, tire size.
And finally, the customers ability to tune the combination.
Conservative is good always.
But pushing the envelope requires knowledge and experience, not guessing.
And I have not even got into carburetors and Fuel Injection.
Pump gas, compression up, timing back.
Like I said, not written in stone.
And a learning curve, always.
Great topic.
Thanks for sharing.
Take care, Ed.
That is correct Ed. I will have more about that in my next video. Please keep watching.
I was loking at the comments and failed to see anything negative or disrespectful so my respects to everyone who chimed in.
I totally understood everything you spoke on; however, I am going listen again another time or two.
My theory is akin to reading a book, one learns stuff that was missed during the first read, or perhaps something becomes more clear.
Thank you for making this video.
By the way, the GM Duntov or 30-30 cam was my favorite cam.
I would set the lash at 26-28 for more low end torque.
Thanks you for the nice comments. AG
Makes sense. I’ve never looked at it like that so it’s a new concept of thinking. I’m always building drag engines with no vacuum and making all the power up top.
Thanks James, If you are racing, that is what you need. I am going to discuss this further in my next video. Thanks for watching. AG
I respect what he just said about David Vizard. And that's the way it should be, he sees a lot of points and recognize that David knows a lot of stuff, however we all have different ways We've Come To What We do. I've been building high performance engines for over 20 years and I still learn and listen to different people. And just because I don't exactly agree doesn't mean they are necessarily wrong. We're too busy trying to show up each other and sound like we all know what we're talking about and are complete experts that we're not open to other opinions. Sometimes two people can have different ways to get to the same end result. And to become better at our craft the things we all love to is having our ears open and listening to others who also know what they're doing. You'll learn and take the best of each thing and then with actual application of your own you learn yourself what works the best for you
All good points, thanks for your comments Corvette. AG
Answer to your final question, while I'm only guessing, I'd say low speed and load maybe, depending on many variables. But as RPM increases the addition cylinder filling would send cylinder pressures way beyond what 87 could resist. I built an 11.6 to 1 408 small block with cranking pressure of 217. It's a tight quench motor with aluminum heads. While it runs very well on the primaries, 93 octane (tunnel ram) it does rattle @ W.O.T unless I use race gas. I think it's because of the same reasons stated above. Backing timing low does not help. My W.O.T AFR is fat as well @11 to 1 so i don't think it's a lean induced rattle. Although I can not rule out poor cylinder to cylinder AFR. Love the tech by the way. I'm always looking to learn more, thanks.
Thanks Bobby, you are braver than me but it sounds like a very nice engine. I am planning to address the points you mentioned on a follow up video so thanks for the input. AG
@@goldsgarage8236 Looking forward to it!
The old GM solid lifter cams had the valve timing and overlap to manage DCR. By closing the intake valve later it allows the SCR ie 11.00-1+ to bleed off cylinder pressure at low-mid rpm when the engine is more susceptible to detonation.
Intake valve closing event is a huge factor in engines running 12.00-1 on pump “Premium” by lowering the DCR.
Aluminum heads, rule on max DCR for 93 octane is 8.70-1… but many push it to the edge at 9.00-1 but be warned.😉
Iron Heads the max DCR for 93 octane has to be below 8.70-1, I haven’t found any data to share but I’d think less than 8.50-1 DCR
Well said. Sir
Thanks Headflowinc. I am planning a follow up video on this subject. Thanks for reminding me to include the issue that engines are more vulnerable to detonation at low speeds. I have researched info in this subject.
My 2018 F150 with the 5.0L has 12:1 . It can be run on 87, but I run 93., previous owner of 67 GTA fairlane 390, 70 cougar, 351W & 79 Mercury Capri with 351W with 289 heads ... Did Not like anything less than 101 octane.
Ultimately the engine died from pre-ignition. Great video Sir.
Thank you Gunny for your comment and sharing your experience. AG
On a 350 Cid truck engine with 422 442 cam 204 214 at 050 dur. 112 lsa. Would a 194 intake valve size be a better choice for velocity and low speed torque. I want to buy some Brodix 180 heads but maybe that's a little too big and I want good mpg. Flat tops .020 down. Quadrojet with factory aluminum manifold.
Thanks for your question Jacqueline. I don't think the Brodix heads will hurt, but they are more than you need to work with the rest of your parts. If cost isn't an issue you could use them but there are less expensive heads that will work well. Hope this helps. Good luck with your build. AG
I sent my cam in to a custom grind shop. Im building a stock FE 428 stock dish 4.13 pistons. After I got the cam back he said to keep compression lower than 9 to 1 and use a stall 2500 converter. Putting it in my 72 f250. Just now learning about cams. Just got my new pistons. Im seeing on my cam info card that intake V Closes at 38 ABDC. I need to assemble the rods n pistons to see what comp height is this week. I think the cam he sent me would raise the compression up if i understand correctly. My heads are 72 cc and gasket .o42. This is my first home built short block.
Thanks Ed, looks like that cam IVC is a good match for 9:1 CR. After you determine the deck height, you will have enough info to calculate the dynamic compression and cranking pressure. The Wallace racing on line calculator works pretty well. Good luck and let us know how it turns out. AG
Thank You. Oregon Cam here in Washington has been building cams for ever. After I do some measuring I will send him another core. I have quite a few here.
My 467 has 10:1 static compression, and 200psi cranking compression. It runs on 91 octane with 36 degrees of timing locked out. No pinging ever.
Also, I recently tested Shell 93 octane. It had 7% ethanol. And I also contacted Shell Canada about ethanol content in their 91 and 93 octane fuel.
They replied just today that their 91 and 93 now contain up to 10% ethanol.
That is good information Pockets, Here, there was a sticker on pump saying that 91 contains no ethanol. I will check again. Thanks for the comment, please keep watching. AG
Try E-85, wow !
I have a 302(5.0 coyote) with 12.5:1 compression and about 180 psi cranking pressure which I run on 91/93
235/237 duration
~535 crank HP
Well then your fuel mixture is below 12.8. There’s got to be a trade off somewhere.
Years ago I rebuilt an LT1 in my 70 Z28, although at the time I was led down a path of lowering the CR, I think stock was 11 or 11.5:1. When we were done I think I was around 9.5:1 and at the same time the GM performance handbook on LT1's listed a offroad cam for the engine, at the time Crane built one to that spec so I installed it. The engine never ran right so I called Crane and the first question "what CR are you running?" He said you need a minimum of 11.5:1 to run it. So I had to pull out that cam and replace it with a lower duration hydraulic. Now for my question; I am about to embark on a Ford 351w build with a brand new 4 bolt block. I am also making it a stroker 408ci. I do not want the high HP but I prefer a high torque motor, it's going in my '85 Jeep CJ7. Two things I would like to know; If I run E85 or 91/2 octane what CR should I shoot for? Also what off the shelf roller cam should I pick? Thanks in advance!
Thanks for the question Dave. With a roller cam, you need less duration, but you have lots of stroke so duration in the range of 210-220 degrees @.050". With 91 octane fuel, 10:1 CR with cast iron heads and 10.5: with aluminum heads. Design for a max cranking compression of 175-180psi. you can find on line calculators for static and dynamic CR and cranking pressure. I don't have any experience with E85 but I think you could run higher CR and cranking PSI. Hope this helps. AG
Great video. I run a w30 4spd cam in one of my 455s and it has 329 duration they are lazy cams compared to todays grinds because of the ramps. But are easy on valve train.
Thanks for sharing Wildrose.
I have a fast ramp cam and heavy springs in my olds 455 and it beats the tar out of the valvetrain especially those ridiculously long pushrods are definitely bowing.
Combustion chamber shape has large impact. One extreme example is the Jag HE V12 engine, has a pocket in the combustion chamber that's 11.5 to 1 on pump gas back in the 80's. Also today's modern heart shaped tight quench wedge shaped chambers are more resistant to detonation. Also good spark control off the crank shaft helps. This is a particular problem on the SBC with it's dist far back and at the end of the cam... that make the spark bounce around, that's no good and that variation can cause erratic spark and trigger detonation. Crank triggers are a must with high compression.
Thanks for the comment John. You have deep knowledge on this subject and giving us something else to think about. AG
I struggle with small block mopars trying to make them run smooth. I put on a set of "fast burn" heads, heart shaped modern design and Wow, what a change. Best small block Mopar I have ever seen.
Always look forward to listening to your channel.... 'down under Oz' 🇦🇺
Thanks RJD, thanks for tuning in and look for more on the subject. Allan Gold
Having quench rather than open heads has huge impact on how much compression you can run.
In Australia our standard 430hp 351c, which I still have in an XE ESP runs flat tops, 302c heads opened up to 66cc’s, F246 cam, Weiand excelerator, 750dp, good extractors straight thru mufflers which make 430hp at 200psi dynamic compression.
No pinging but low gears and light car has a big impact on how much compression you can get away with using pump fuel.
Forgot to add it’s a long rod 351c, which also lowers dynamic compression, uses a 302c 6” rod rather than 351c 5.78” rod, has modified pistons.
Hello Chris from Australia. Those are good numbers for a 351 and 200psi. What octane fuel are you using? AG
@ Hi, The highest we have which used to be 100octane but now can only get 98, but equals around 94/5 in USA. I have 3.5 diff gears weigh around 1750kgs and top loader box.
OEMs (and those of us working on emissions reductions in hot rods) have other tools as well. The decrease in fuel mileage you mentioned can be combated with variable valve timing, EGR, and even Atkinson-Miller via valve timing. The tough part (which is what I’m working on) is variable duration as well, in order to maximize power when using race gas. There are other tools I’m also working on, but these are proprietary (my goals for my 4.6 liter Ford Mustang are 450 hp / 45 mpg on pump gas - not at the same time of course).
Thanks Ed. those are all good technologies. Let us know how your Mustang build goes. AG
2, 3 or 4 valve heads?
@@johngregory4801 3 valve. I chose 3 valve because I’m removing the camshaft (and all the junk in the middle related to the lash adjusters) and replacing it with a pneumatic valve actuating system. 3 valves gives about the same performance as 4 but requires less compressed air for the pneumatic system. The pneumatic actuators are electronically controlled so i have COMPLETE freedom of valve timing specs.
@@ehb403 COOL! Who's it from? I've seen pneumatic valve spring systems before, but not pneumatic actuation for valves. Talk about being able to optimize timing for all revs and all conditions!
@@goldsgarage8236 The engine is from a Mustang, but it’s going in my Ford Fusion…mainly because my wife nixed putting it in the Lincoln MKZ (same car with nicer options and accessories) since it already has a 400 HP engine in it from the factory.
Thank you for all the information you put out sir, I always learn something new every time 🙏🏼
Thanks Gabe, you are motivating me to keep digging. Watch for more coming soon! AG
This is a late comment but you also have to consider if the engine has iron heads or aluminum heads. You need more static compression for aluminum heads because the aluminum will act like a big heat sink and wick away all that heat, iron heads will retain more heat and build more pressure. Heat builds pressure, pressure builds power.
Good info, thanks for commenting Jeffrey. AG
Just as dynamic compression, set by the camshaft events greatly influences cranking cyl pressure, a running engine has variables that determining the octane requirements. A high compression race engine with over 14:1 calculated compression ratio with a relatively short duration cam could reliably run on 87 octane gas no problem, if the torque load was kept minimal. This would require a throttle opening to maintain relatively high intake vacuum. In this case, the engine can't develop high combustion pressures/temps associated with detonation. There's a ton of other factors at play, combustion chamber temp and efficiency, total ign. timing requirements, accuracy of maintaining proper fuel distribution and ratio evenly across all engine loads and cyl to cyl, etc...
Short answer, in an old school carbureted muscle car era engine, I would agree with your assessment on taking a close look at cranking compression pressure as a good overall indicator of detonation resistance. Unless someone was willing to spend a ton of money to modernize all the development shortcomings due to age of these old engines, and taking the owners dedication and ability to monitor for signs of detonation, I'd say anything over 10:1 would really be pushing it when combined with a typical hot-rod street camshaft.
Thanks for the input Jeff. AG Look for future videos on this subject.
Eric Weingartner's Videos on camshafts and cylinder heads is pretty informative.
Thanks for the tip Jonathon. I watch Eric also. AG
I have an L72 with fresh .030 over bore and 11:1 forged pistons using stock cast iron heads with oversize exhaust valves. A concours nut and bolt restoration was completed in 2019. The car overheats and I am unable to drive it. I installed a new DeWitt radiator to help with the cooling but to no avail. I then checked compression and found it to be 250 psi all cylinders. The original cam was reground to stock specs during the restoration. The intake is a factory 2 plane (5069) and the pistons are TRW. Everything on this car is new or reconditioned and now has less than 300 miles. I am using straight 104 leaded. The timing is whatever Corvette Specialties set it to. I am using stock exhaust manifolds w/2 1/2" exhaust pipes and stock 355 rear end. The car is very difficult to take off in and between that and the overheating is not much fun to drive. Do you think that the compression is the cause for the high temperature? Any advice would b much appreciated. Thank you.
Thanks for the question David. According to the GM manual, the cranking pressure for an L72 425HP 427 is 150PSI, even though it was 11.0:1 Static CR.
I suggest we start by recalculating or verifying your static CR. The bore is 4.25 and the stroke is 3.76. You need to know your combustion chamber volume, head gasket thickness and piston dome volume. If any of those things were changed during the rebuild, machining the heads or block surfaces, thinner head gasket etc, they may have increased your static CR.
To determine your dynamic CR and cranking pressure you will also need the connecting rod length, 6.135" and the IVCP (Intake valve closing point) of your camshaft. Unless you already know this or the engine is accessible to degree the cam, it is unlikely you will have this information.
Since your cranking compression is so far off, and the engine also does not run well, I am suspicious that something is wrong with the assembly. For example of the timing chain/gears were aligned incorrectly, (camshaft advanced a link or two) , that would close your intake valve even sooner, trapping more compression. Similarly if there were mistakes in the camshaft regrinding, same result.
This would be an interesting project.
Do you have the cam specifications? degreeing the cam would determine if either of these things were true. That would mean determining the centerline of the intake valve and then closing point. IVCP
I would start with degreeing the cam. The engine has to be out of the car to do this.
Let me know if this is helpful. AG
Looking at my response from last night. Two other possible causes of your condition could be ignition timing or a vacuum leak. Your timing should be about 36 degrees total at 3000 RPM with the vacuum advance disconnected. You should be using vacuum advance connected to manifold vacuum below the throttle plates. (not port vacuum) Also check for vacuum leaks. There is a large vacuum port at the back of your carburetor below the float bowl, hard to see it and I have seen this left open before. That would cause extreme lean condition, overheating and terrible running. This still doesn't explain 250 PSI which is too much. AG
Check your thermostat in boiling water to make sure it opens when it should I found most of them don't work nowadays or when they should at least The most accurate ones I found are the Edelbrock thermostats
We run over 16 to 1 on Pump Gas with Cranking comp of 220 we also don't go near Peak TQ or load it going down the road and chance to Race gas at the tracks. There is lot of work goes into being able to do this but it can be done.
Thanks Jeff, I don't even know how you would get 16:1? AG
@@goldsgarage8236 it’s a 712 inch all billet semi Hemi from Todd Goodwin it makes over 1300 hp. We Run Sick Week and Hot Rods Drsg Week. N/A it’s going 7.71 at 174 1.11 60 ft. Not to many people understand pumping losses from lift and duration, ramp design effects on it. Good information overall
Direct injection is the key to running on pump gas with high CR. My 2023 F-150’s 5.0L V8 engine is running a 12:1 compression from the factory and can run 87 octane up through E-85. On 91 octane the crank ratings are 400 HP/410 LB FT from the factory. On E-85 it’s 420 HP/430 LB FT (also from showroom floor). It actually uses dual PFDI injection (One DI and one PI injector per cylinder.
Thanks for taking time to share your comment James. AG
Yep this is correct and if you if you follow his 61 versus the 81 after bottom dead center that's where he gets it back on the right now yep and I believe that will and his destination is going to make it to the definition for gas cuz that's what we're going to do run pump gas and see if I can do it with 13 to 1 or 3:27
Thanks for your comments. AG
FYI the Mercedes M276 DE35 is a factory 12.2:1 compression ratio. I run mine on E15-88 , pump gas is no problem with high compression if the motor is built correctly to reduce hot spots in the combustion chamber that can trigger pre-ignition/detonation
Thanks for the info 100. AG
225psi cranking compression, and pump fuel for my street daily driver 379ci standard 4" bore 4 bolt main small block combo. Have run as high as 250psi with a Holden 6 on pump fuel. The other street strip daily driver combo of mine is a 327 2 bolt main 14:1 compression combo
Thanks Brendon, Are you in Australia?
What kind of dyno numbers does something with that much cranking compression make?
@@dennisrobinson8008 How many times do you ask for forgiveness at night knowing you have 14:1 on a 2 bolt? Just kidding but still, goes all against the 1970's tradition of dissing the 2 bolt.
VERY WELL PRESENTED. ALSO LOBE SEPERATION ANGLE. L88 WAS 114. TIGHTER LIKE MOST COMP CAM STREET CAMS ON 110 MAKE MORE CYLNDER PRESSURE WHICH EQUEALS MORE POWER. ALUMINUM HEADS ALOW 1 POINT MORE COMPRESSION ON SAME OCTANE..180 TO 200 PSI ON A PERFORMANCE STREET MOTOR RUNS NICE. BUT NOT SO MUCH FOR TOWING BECAUSE OF HEAT GENERATED LONG TERM
All good points Hank, thanks for contributing. I will be making more videos on this subject, watch for it.
Definitely good content I have that dilemma now with a 400
Thanks for watching and commenting BB. AG
I think You should be able to run off of 87 with this compression ratio! Here are the reason why: 1. Rod ration is a factor; the higher the better; 2. Combustion chamber design/efficiency; 3. Piston design/quench; 4. Constant cooling temp and adequate cooling system/components; 5. Good fuel quality/low ethanol content/low moisture; 6. Precision fuel metering/A F Ratio; 7. Vehicle weight; 8. Gearing and Transmission; 9. Appropriate Cam selection/Timing; 10. Properly machined and set-up Cast Iron head; 11. Correct Aluminum intake manifold! I also think a good oil and standard volume oil pump would be the right choice for a street application. 12. Properly sized exhaust system should complete the total package..
Thanks rjordanar, lots of thought, thanks for your input. I am planning a follow up video to address this soon. Please keep watching. AG
What is not considered is why the intake closing is delayed. CCP does not consider actual running engine at higher engine speeds. The late closing allows inertial to better fill the cylinders so even though the engine degrees of duration with a closed valve is reduced on compression the cylinder has packed in a larger mode dense charge. The bleed off that is seen at low speeds and cranking is now negated. Dynamic cylinder fill takes over and the demand for higher octane prevails.
Very good point Don and so high speed detonation may occur. The difference is that at high RPM, detonation doesn't have as much time to do damage. AG
I worked in a building that one business unit did QC for refineries and stored aviation samples from plane crashes for testing. One thing today is its not really fair to call fuel octane still, it's blends of multiple carbon chains, many lower than octane, i remember as a kid my dad burning bush piles with purple and when the match was in the air you were heading the opposite direction and the whup went through you, today sometimes you can't barely get a fire to lite
interesting point, thanks for the comment hardtail. AG
My static is 10.2:1 ish. I have a comp XE266HR12. Warm cranking compression is between 162-165 on all holes at 5200’ elevation above sea level. Adjusted to sea level 192 cranking compression. 4000+ lb manual Bronco. Runs great on 91 @ 32 degrees
Thanks Piercer, where are you 5200' above sea level? AG
@@goldsgarage8236 Los Padres National Forest an hour north of Los Angeles.
I had a 64 Chevy II that had the “140” (last 3 numbers) cam and 12.6:1 compression ratio according to the guy that owned the car before me. The car had a 4 speed and 4:56 gears. It ran on the street fine but would really wake up at 5,000 +!
Sounds like a fun ride, Thanks for sharing. AG
Thank you for your wisdom....I've watch David Vizard and many others...I want to switch to BBC after a life time of being a 327 fan. I appreciate the fact that you guys are willing to share your knowledge...my next project is a 1968 El Camino with 4 speed 373 gears and red line of 6,000 RPM. This is a street car that i want to be strong as i can get with a 454 bored to 60 over or maybe a 496 stroker with iron heads....any advise would be greatly appreciated. Keep up the good work.
Thanks Michael. I recently built a 427 that is very similar to the ZZ427 GM Crate motor. There are videos about it and another one that I built on my channel. I will be installing this engine in a 1966 El Camino in two weeks or so. I will be making videos about the conversion from a SM. Watch for it.
Hal's dad gave him a 67 SS El Camino with a 396 4 speed GM 21 muncie . It was black and was amazing . the boboso traded it for a 1969 Triump 650 motorcycle . We all told him he f up .
@@jimmywilkinson9190
IDK... if it was a clean Bonneville, I'd take it over the El Co. Big money for old Triumphs. J.S.
We ran our 482 big block Chevrolet with 12.5:1 on 91, for YEARS in a boat. Kept the timing at about 36 never had an issue. My current engine with 11.8:1 runs great on 91 with 34 degrees, been in the car since 2008 with EFI controlling the fuel.
Good reference info bigblock. EFI will help for sure. Thanks for sharing. AG
What temperature engine ran in boat ?
i was wondering why you don't use Brass freeze plugs, i enjoy listening to your video's as we are never to old to learn what you have to say even tho, I am 80 yrs old and still enjoy hot rods.
I have a running project 1940 ford cp. with a 327 with a tir power carbs setup and a new 5spd TKX tranny with a dodge 8.3/4' & it's has a 4.10 rear axle ratio. I'm using 80's 350 truck heads with the angle spark plugs to lower the compression to about 130 psi so, I run 87 octane pump gas.
.
Wow, 80 and still digging, I hope to do the same.
That will be a cool rod with the tri power 327. Actually i usually do use brass frost plugs and i am installing them on my current build for Will Casey. I just happened to have the steel (galvanized) ones . Steel plugs will outlast us but brass looks cooler for sure. AG
good info probably should also mention how cams with large overlap will effect cranking compression. Mine makes only around 90 psi cranking pressure but has a large overlap and duration. Effectively pushing combustion out intake port at low speed. The compression ratios is around 9.5:1 engine is turbo charged and makes 700 hp from 2.4 liters at 8500 rpm.
Thanks for your input, onefasthatch, That is a big cam! I am going to discuss this further on my next video, I hope you watch for it. AG
Overlap effects idle quality. Intake closing effects cranking pressure. More overlap will actually increase low to midrange cylinder filling and that is why dirt track guys run a 107 or 106 lsa cam instead of 110 or 112. The 106 - 107 will pull a lot harder off the corners but the idle quality will be horrible. If you are pulling up past 7k rpm the higher lsa 110-112 would probably be better because of better higher rpm cylinder filling.
3rd gen mini cooper S has 11:1 comp (250 psi cranking spec ) and requires at least 89 octane. From the factory also running 8-9 psi of boost
Here in Australia we have at the pumps 91, 95, 98. What is max compression for using 95 ? in a 5 .0 V8 on a carb.
Thanks Jim. That depends on a lot of things. Generally speaking 95 octane should be safe for 10:1 CR for cast heads and 10.5:1 for aluminum heads, however camshaft timing and even the pounds of car / ratio to cubic inch and gear ratio is a factor.
My rule of thumb is 160-180PSI cranking pressure which verifies your DCR.
Hope this helps. AG
great video, the thing that NO one ever talks about is how many BUMPS on the comp gauge is required to get the needle to 150PSI? Hydraulic lifters give mushy valve action when cold so thats why we test at operation temps. Ive done 100s of comp tests at GM on thier dynos in australia and the SLOWEST comp needle movement was from the LS series of engines, they required 8 comp bumps to get to the desired 150PSI with a 10.4:1 engine! But when we took out the corvette cam & installed a 5.3 truck cam the comp was now 165psi & it only took 4 bumps on the gauge! testing on the truck cam bought peak torque and horsepower down the RPM line about 1000rpm. My boat has a 351c with 302c heads & laid back chambers to give a measured 10.2:1 comp, with a 218 cam. comp gauge reads 165psi in 2 bumps on the gauge and it just likes 95 ron fuel ( your equivelent 91 octane)... I really enjoyed your video, keep up the good work.
Thanks Wayne from Australia. Did you know, the number 1 city in terms of clicks on my site is Milbourn Australia and many other cities in Australia are right up there so thank you for the great support. I think the Wallace Racing guideline is 7 bumps but for the reasons you mentioned I think you should keep going until the pressure reading stops going up. Usually that is about 4 bumps. 91 fuel should handle 165psi easily. Hope this helps. AG
What kind of exhaust manifolds on the cleveland in the boat ?
you mean MELBOURNE. Thats where im from. We have some smart people in the aftermarket head and manifold design. CHI heads ,AUSSIESPEED manifolds YELLATERRA heads& valve train SCOTT COOK cleveland heads , to name just a few.@@goldsgarage8236
I worked at a Chevy dealer in the 1960s, I did alot of tune ups, and we always performed a compression test. most cars fell into that 150 psi range. I worked on alot of Corvettes and some of the HP engines would push the psi well over 200 some as high as 250
Very interesting Monty. In the 1968 GM manual specifications, the highest cranking pressure for any engine is 160PSI, except the Z28 is 190PSI. Do you think carbon build up could be a factor?, or where these engines modified? Thanks for your comment, we are learning from your experience. AG
FYI i built a 383 sbc that was run on the dyno it made 437hp on pump gas , cranking comp. was 195 psi.
Thanks jiggsman, that is a good number for a street 383. There is a video on my channel of Tom Winkler's 383 that made about the same. AG
12.5:1 SCR on pump gas? Absolutely! Even with steel rims. Yep! Seen it done many times actually.
Definitely premium gas, 93 octane from my experience. Can't comment about anything lower, but I have heard it can.
I remember a time I believed in some of the stereotypes, and at the time they seemed correct because it typically came from people who seem to know what they were talking about, however I kept going back to the first time I seen very high compression with steel heads on pump gas. And that would be the engine my stepfather built. He was running 12.5 to 1 static compression ratio, Steelheads and ran 93 in it. No problems.
Regardless this is when I was first starting out and learning everything. Buy my mid-teens my brother and I were already doing engine swaps in manual transmission conversions etc etc, and we were building what was considered high performance engines at the time, in the early 90s 400 or 500 horsepower was extreme horsepower, lol!
Anyways what has seen my stepfather and others do always nagged at me when I heard the so-called experts on compression
Now many many years later, when forced induction is in its prime, I continue to hear misconceptions about compression. People have this idea that when you use the force induction you have to go with extremely low compression which is not accurate. I am running 11.0:1 SCR with twin turbos. My brother 10.5:1 with a turbo. On premium pump gas.
Don't get me wrong, we have Holley EFI systems which help with tuning and getting the best out of everything, however really is more based on putting the correct components together. Too many people look at the individual parts and or maybe a couple of them together. For instance you may look at the camshaft with cylinder heads or something like that when in fact it is everything all together and even as this guy has stated which is very important, is the intended use. Many people don't consider the load, factors that play such a big role in what you are doing
Good comments, you have given this subject a lot of thought. Thanks Corvette. AG
I think you can run 87 with a 12.5 compression motor if the cam has plenty of overlap, reduced spark timing, and running only at lower RPMs with light throttle. Didn’t Crower cams offer cams to run high compression engines on pump gas?
Thanks Scott. Cams with lots of overlap also have a late IVCP which bleeds off compression at low speed. AG
Thx for putting up such Rare & Helpful info on a very hot topic for us hp factory iron guys....It really Is a comparison & engine Octane fueling Dilemma because the popular 0.050" lifter spec cams & the typical solid lifter 0.020" cam card timing data Is Way Different from the factory 0.006" lift SAE valve timing specs......Even using Long ramp Bleedoff cam timing, Chevy Did affix Octane Warning stickers to factory Iron head, L88 engine that Minimum rated Octane was Ron 103 & Mon 95, with Mon rated fuel Preferred.....Why would Chevy bother with that warning If Lower Octane Was Not a Problem ?? ....Looks like Chevy Didn't put much faith in the DCR effect ??.....With U.S. Pump gas 92 AKI (R+M)/2 rated at 88 MON, how is that supposed to work with factory Stock shim head gasket & Internals ?? ......Around engine Max Torque Rpm range, the cylinder Does fill Beyond the IVC point, nearly to Full BDC cylinder capacity & Nullifies the Lower calculated Dynamic CR is Probably why.....Maybe the clever use of "Squish" optimized Aluminium heads & smart ECU Detonation sensor designed ignition system can let the Stock engines run flat out Again on the current pump gas Octane problem.......
Lots of info, thanks for sharing Tom. AG
Well, it's quite possible it could. I'm at 3500 ft elevation, so a hot street engine in most cases needed 11.5 static compression and depending on the cams intake closing, it could definitely run great on pump. Good cylinder head chambers, and proper quench are also important.
It's also worth mentioning that today's Ethanol blended fuels have a different Stoic ratio, it's not 14.7 to 1, it's 14.01 to 1, so a proper tune will need to be richer that most people think. And it won't require alot of timing because the fuel burns quicker. If you tune a high compression engine as If it was forced induction, it will be fine....
Thanks for the info Duane. We are 753 feet above sea level so that s not an issue here. Thanks for the info about stoic ratio. We tune for results on the dyno, usually about 13:1
@duanedahl8856 point is correct regarding the difference in air/fuel mixtures between straight gas and gasohol. Inherently today's engines don't make any less power on modern, alcohol-blended fuels versus gasoline from the "old days"; they just burn more of the new stuff to do it. In fact, modern fuels with higher alcohol content can actually help to enable greater power because the charge cooling affect of the alcohol permits more dynamic compression and/or timing (i.e., higher cylinder pressures without detonation).
The issue with cranking compression is the rpm the engine cranks at. Street engines with higher tension rings tend to turn over slower than a comparable engine with low drag rings. Higher compression can cause a slower cranking RPM if the plugs are left in the other cylinders. I typically remove all the plugs. This gives a better picture of the condition on the cylinder being tested.
Sizing cams is an art. Bore to stroke ratio does come into play and it's opposite of what I thought it would be. The longer stroke engines appear to be more fickle with duration than shorter stroke engines. This is for racing applications and may not matter for street applications.
Those are all good points Brad. It is good practice to remove all the plugs and have good cranking speed when taking a compression test. Thanks for your input. AG
Can you explain the benefits of hi compression motors? Can you use less fuel and more air? How are direct injection gas motors making safe hi compression motors on reg fuel ?
Thanks for the question Taras. That is a great suggestion, you just gave me an idea for future video on this subject. Watch for it and let me know if I answered your question. AG
Taras, did I answer your question on the last video?
@@goldsgarage8236 didn’t watch it yet. I’ll do soon soon. Can’t wait
11:7:1 guy told me colder plug no issues
They changed cam during bottom end upgrade it took way too much vacum idles fine worried about detonations. Vacum canister or pump he does not know where my original cam is. I wouldnt buy a flat tappet now with issues. Old was 1600 to 7k rpms new is 3k through 7k sounds great taking it cross country
A 7000RPM cam will have lots of duration and late IVCP to help bleed off that 11.7:1 CR. Thanks for sharing. AG
@@goldsgarage8236ty for info and r3sponding. What should i do abou5 vacum loss?
I ran my 68 Pontiac GTO HO 400 on 87 pump gas. Listed at 10.75 to 1 bored it 60 over probably @ 11 to one then. No problems.
Another good example of what I was talking about. Thanks Tom. AG
I'd push 11.5 1 with fast swirl aluminum heads and the right dur cam. The higher a cam lobe lifts the valve off the seat it does hold the valve open a little longer. But few cams are streetable past using a 285 dur cam.
Thanks Paul, 285 is probably a good number. AG
I have to chuckle, watched my first video of yours and asked a question to then refresh my computer to land on my second video of yours that looks like its going to answer my question lol.
Thanks heshtesh. Glad you found what you were looking for. AG
12.5:1 on pump gas, is doable depending on what ignition timing one is running, depending on altitude, and how hot and humid the place is. Also how hard you're running the motor.
Thanks Sep. That is all true and I plan to cover this issue on my next video on this subject. Please watch for it. AG
So, essentially, however many degrees after bdc the intake valve closes will have the largest say on what the compression ratio is?
So I see this conversation come up quite a bit with regards to making power on Coyote applications where people are trying to make 750-800 plus hp on boosted setups on pump 93. Can it be done? Yes, but they don’t like it when you tell them that it isn’t a great idea and it likely won’t last very long without adding octane additives or switching to E85 or race fuel.
Thanks for the comment Brillo. That is crazy HP on the street. AG
I once ran a 327 sbc with 10.5:1 compression with ported camel back heads, a pretty hot
cam, headers, a Holley 600 (tuned) with a Mallory Unilite ignition. Ran very well for several
years on 91 octane gas (NO pinging). Good aluminum heads might be better for more
compression. I was probably putting out around 375-400 hp. Only reason I was "slow"
was because I had a 3.42 open rear end in a 1972 Camaro. If I had a 3:73 posi, I would
have been MUCH faster, especially with really good tires.
Thanks Hans. Gearing helps. I installed a 4.88:1 gear in my Camaro in 1969 and it was still there when i bought it back. Lot's of fun on the street. Sounds like you built a nice SBC. AG
Would you know perhaps what would be a better camshaft than factory on the vw 2 litre air cooled kombi, I think torque would be more advantageous, unless you think original cam is still a good choice. Thanks buddy 😊
Thanks for your question Harry but I don't have much experience with this engine and don't know enough about the application. Consider the end use, daily use vs. race, weight ratio, lb./cu. in. gear ratio, type of transmission, RPM range where you will need the performance etc. Hope this helps a bit anyway and thanks for watching. AG
@@goldsgarage8236 ok cool thanks 😊
How do you calculate cranking pressure when designing a build?
First calculate your static CR with the Summit on line calculator, just google it. Then google Dynamic CR, a Wallace Dynamic calculator should come up. Just fill in the required information and you will get your DCR and cranking pressure. Hope this helps. AG
It does. Thank you. I was getting a very low pressure when using a different calculator on Wallace. The dynamic compression ratio calculator on Wallace is the correct one to use as you say. That calculation also includes the dynamic pressure calculation along with the dynamic compression ratio. Thank you sir for clearing that up.
Thank you for the video. I'm learning all I can about this stuff. I'm about to take a healthy 6.0 and put a cam, springs, lifters, etc in it. I like that you are conservative. So, I have two questions. First, this LQ4 engine comes with 317 heads. The engine has a 9.4 to 1 ratio stock. I also have 706 heads from a 5.3. Everyone is telling me to use those. They would boost my compression to around 10.5 to 1. Do you think I would still run fine on 87 octane? Second, what cam would you run for daily driver, a bit more power, and mileage?
Thanks for the question Dylan. I am not as well informed on LS engines, however if you are building high compression, I would use the best pump fuel you can get. As for cams, the LS engines doe not need as much duration as the GEN 1 engines partly because they are all roller and can accelerate the valve faster on the ramp. Check the IVCP and calculate your DC and cranking pressure before you decide.
The final result depends on many factors, the power/weight ratio of your car, gear ratios etc.
Hope this helps. AG
I had a 427/ L88 and was out one night and needed gas to get home and only could get my hands on 87 octane I had to back off the timing big time to get home without pinging every time I touched the gas.
Thanks John, not surprised to hear. You were pretty fortunate to have an L88. AG
So my stroker 427 sbc has a cranking compression of 210 psi. The builder said it has a dynamic comp of 11.1 to 1 he recomended i run a minimum of 100 octane i so so by adding an octaine addative. To no ethanol 91. Cam has 272 duration at 0. And a 109lsa on exhaust 112 on intake. Is he out of line or could i run 91 octane without ehanol. I believe that fuel is non oxygenated as well.
Thanks for the question Chad. I think your engine builder is correct. With 210 psi cranking pressure, you will need race fuel.AG
So when you bleed off that higher compression with that cam design? Is it just wasted compression or what am i missing here ?
Great question Boss. Let me try to explain.
Air and fuel mixture has mass and so it also has inertia. The inertia is proportional to speed (RPM) of the engine.
At low RPM the air fuel mixture has very little inertia so after BDC the piston is able to push it back into the intake plenum until the intake valve closes, usually about 40-65 degrees ABDC. This reduces dynamic compression as nothing is compressed until the intake valve closes.
This is called reversion and is what causes the rough idle and poor low RPM performance with long duration cams.
At high RPM however, the mixture is entering the plenum at a high velocity and actually compresses against the closed intake valve. At the overlap TDC when the intake is opening and the exhaust is closing, that inertia purges out the exhaust gases until the exhaust valve closes, then rams into the cylinder until the intake valve closes, almost a supercharged condition.
A long duration cam has more overlap at TDC which helps high RPM performance, and a late closing point for the intake valve which reduces detonation.
If you have lots of (static) compression, you need a high duration cam and vice versa.
I hope this helps, please let me know. AG
@@goldsgarage8236so if you have a cam with shorter duration with a smooth idle i think I'm saying that correctly you would need higher octane fuel ? Thanks in advance .
150psig @ sea level is 10:1 compression ratio, and the higher you go the worse that is
Direct injection & advanced engine electronics is how my turbo 4 runs an OEM 13:1CR on 87 octane gas in Buffalo NY
Thanks for the comment Krak. AG
Can we polish the top of the piston and the combustion chamber to keep detonation low?
Good question Topgun. I don't think it would make much difference on anything aluminum but a sharp edge or rough surface on cast iron could potentially glow and cause pre-ignition. AG
I should have also mentioned, built up carbon in the chamber and on the piston is more likely to cause pre-ignition. AG
@@goldsgarage8236 how much compression is safe with iron heads set up properly for street use?
i think of it this way. The Pontiac i am building now has about 10.4:1CR with steel heads. The dynamic CR and cranking pressure are more important. It will have under 180PSI cranking pressure. You can calculate all this using on line calculators, Summit for CR, Wallace for DCR. Your camshaft IVCP ABDC is a big factor in this calculation.
If you aim for these levels use the best pump fuel you can find, manage your ignition timing, keep operating temperatures under control
@@goldsgarage8236 thanks for the tips! I've heard chrome valve covers and oil pans retain heat. Is that true or just hear say.
Cranking pressure is measured at very low RPM. You might even be getting over 100% VE at high RPMs. How would that effect the pressure then?
Good point Scorpion. VE at high RPM will increase peak pressure and MEP, which is the average cylinder pressure during the complete down stroke. Typical MEP would be 10-15 times atmospheric pressure. AG
Great Video!! 22r (2.4 liter solid cam) street driven Weber 32/36, dual plane, stage 2 cnc’d heads with +1mm valves all port matched, ~9.8:1 , mid length header with 2.25” exhaust.
Currently have a Crower (EFI stage 2) 216/220 @ .050”, advertised 270/276 with 430/430 lift and 114* LSA, which was obviously not the LSA I thought I needed, but I like the specs of the rest of the cam!
Crower has the stage 1 Carb version (same specs as efi stage 2) with a 108* LSA, which I currently plan to buy to hopefully run 87 and get 25+ mpg city (with 3.73 gears eventually, 3.07 now).
Your time is appreciated, and your thoughts greatly appreciated.
Without dynamic compression measured, is ~10:1 on 87 octane likely, or is my head still in the clouds?
Rare to find someone that tailors to street driven vehicles, so I’ll be checking out your other videos for tricks before I pull my motor back out.
Currently have 9:1 pistons with 114* lsa cam and bought KB’s 9.7:1 hypereutectic and shopping for a better cam.
If it won’t run well enough to stick with 87, it won’t stop me, but don’t want to ‘tune myself to death’ trying to accomplish the impossible if I just need another octane point.
They have a stage 2 cam with 226/236, 286/290, .429/.443 with 108* lsa (which might be too big for low end desires and possibly too much dynamic compression to risk detonation but recommended upgrades of engine requirements align but they project a 3,000-7,000 power band versus 2,200-6200 for the stage 1) or another option is having them custom grind one similar to these specs, maybe more exhaust lift and/or tighter LSA.
Thanks again for the video!
you talking about the Toyota engine? I always wanted to see how much they would make! I heard the 20 r head made more power if you know is that true?
@@johnsheetz6639 every 22r owner that has spent a lot of money will tell you they won’t make much hp but the torque is pretty decent. I’m $3,000+ invested in the motor and with manual steering and electric fan (less parasitic loss than clutch fan) and 9:1, I maybe freed up 115-125 hp to the wheels. It’s not a very satisfying engine to sink money into but can expect to see 200,000 miles, it appears.
They are described as tractor engines and I agree, so depending on what you want to use it for, you’re probably better off with any other engine in the world for hp unless you boost it… and even then, there’s probably a better alternative.
@@johnsheetz6639 as for the 20r head, they have a hemispherical combustion chamber and a straighter path for air to flow in the ports for better velocity, so depending on your build, they could be a bolt on bunch of fun. They are also rare to find, which drives the price up.
@@Dube7666 that's what I heard before and the Jeep 4 L is one that's kind of the same. They both remain two of my favorite bulletproof engines though. They are engineering perfection for getting you there and back!😎
@@johnsheetz6639 I always like the jeep cherokee and thought a low rev turbo with a straight 6 would have a lot of torque… but the Jeep emblem cost on every part adds up before it even begins.
Choose the powerband you want to run. Assuming your engine will make power at a given rpm. 3500 and up can work on a hi flowing headed 454
Thanks for all your comments and input PMD. AG
Interesting Camshaft comparison at video 13:41....Are Both Camshafts Actually Measured using Exactly the Same measuring Method or is Any of the IVC° data Estimated or Equivalent Computed as this is 1 OEM Solid compared to Aftermarket Hydraulic cam ? ......
Exactly did Chevy Measure their Solid lifter cam IVC° & Intake Duration ? .....I don't think 0.050" or 0.020" at Lifter Check Height was used.....Anyone know for sure ??
Good question Tom. I calculated the effective IVC based on the other known factors. It would be impossible to measure with a degree wheel because of the soft ramps. Pretty sure the .050" measurement was not common then. We just degreed to the centerline. Thanks for contributing. AG
Thx so much for responding....I'm really Interested in this topic as I have a Mopar build going on with a solid FT Cam & concerned about same Expected octane issues....My error on the L79 OEM Solid lifter spec, I know it's Hydraulic also....Why not Compare both cams Measuring at SAE 0.006" Lifter Check height (using a solid lifter) Similar to what Factory spec was for the DCR calculator input value ? .....I'm real interested in what's Actually happening at between 0.006" & 0.050" valve lift & think the 0.006" lift point would More validate the OEM extended lobe ramp effect issue on Actual IVC° point.....Thx again,...Tom..
Didn't the l88 Corvette have a decal on the shifter console saying must run high octane fuel?
Apparently it did John. 260 Sunoco 100 octane was readily available at that time. Sorry I missed your comment earlier. Thanks for posting. AG
Your video was excellent!
I am in the process of selecting an engine builder to build a new 421ci small block Chevrolet using a Dart SHP block with a 6-71 blower and AFR195cc heads with a 75CC combustion chamber. One of the items we are discussion about is camshaft profile and piston dish selection. He is proposing a 36cc dish piston (off the shelf), and a 255/239 .600/.580 114LSA hydraulic roller camshaft.
What do you think about this combination?
Thanks for the question 331. Looks like a nice very high end build with all good parts. You might calculate your static and dynamic CR and cranking pressure to see if it works with the blower. Is this a pump gas or race fuel engine? What % boost are you planning with the blower?
Your blower will increase the dynamic compression pressure and MEP, (Mean effective Pressure) That is how it makes power but there is a limit before the risk of detonation on pump gas.
Bill Little, if you are watching, can you comment please as you have experience with blowers? AG
@@goldsgarage8236 thank you very much for the response.
This is a pump gas street driven vehicle, with between 7-10lbs of boost (to be tweaked on the dyno with the pulley setup).
Thanks 3310. i have sent a text to Bill asking him to look at this for me. He has good experience with blowers. AG
Hmmm doesn't bleeding off the compression with cam duration defeating the purpose of gong with more compression to begin with?
Good point Alonzo. Here is how it works. The valve timing bleeds off compression at low RPM only. The fuel air mixture has mass. At high RPM the mixture is travelling at 200-400 RPM so it also has inertia. This helps to fill the cylinder on the compression stroke and purge the mixture on the overlap cycle. Dynamically you will have lots of compression. Engines are more less vulnerable to detonation at high speed because the flame travel takes time and the piston is moving rapidly. Hope this helps. AG
Alonzo, I just caught a mistake in the comment above, the fuel air mixture is travelling at 200-400 MPH, not 200-400 RPM. Engines are LESS vulnerable to detonation at high RPM. AG
What is cranking pressure and how do you figure out how much
Good question John. Cranking pressure is simply compression pressure that you can measure with an inexpensive compression gage that you can buy from any auto parts store. it screws into the spark plug hole, (disable the ignition) then crank the engine over a few revolutions or until it stops climbing.
For a street engine on pump gas I like to see 160-180PSI (pounds per square inch).
Compression makes power but if you have too much you can cause detonation which can damage the engine.
To calculate it on a build, first determine the static CR. You can use the Summit on line Calculator. You need to know your bore and stroke, combustion chamber volume, piston dome volume, deck height and head gasket thickness. For street, aim for 10:1 for steel heads and 10.5:1 for aluminum heads.
Then you can use the Wallace Dynamic Compression On Line Calculator. Now you also need to know the connecting rod length and the IVCP (Intake Valve Closing Point) of your camshaft.
The result will be your dynamic CR and cranking pressure.
Hope this helps. Let me know. AG
How to consider or calculate cam and gear ratio relation ?
Thanks Bryan. Generally bigger cams don't make a lot more torque, they just raise the RPM where that torque is made. HP= torque x RPM/5252. So if you use a cam that produces torque at higher RPM, you need gearing that raises your RPM and takes advantage of it. So as the operating range of the cam increases, the gear ratio should increase proportionately. Hope this helps. AG
What fuel should I use for 10.9:1 compression on the street
Thanks for the question Chad. I would use the best pump gas you can get. AG
Hi, just a quick question. My 406 pontiac has 190 psi on 6 out of 8 cylinders and 210/215 on the other 2. Wet compression test yields another +30 to + 40 psi ranging from 220-250. i have an excel file of exact measurements I'd like to email for a 2nd opinion but just curious if what I've written leads you to believe the rings are probably toast. Dynamic compression test next while it runs coming up. Leak down % #'s are from from 8% to 17%. TY
@@ubethejudge69 I’m travelling right now so responding from my phone.
Don’t over react.
Your leak down numbers are not bad so I think the rings are ok. Higher compression in two cylinders could be carbon, or in accurate reading. Run it and check again.
Even 190 is high for the street. How does the engine run?
@@goldsgarage8236 Appreciate reply while travelling. I didn't think of carbon - good point. I have some pics of pistons from scope - maybe some seafoam would clear that up. I just want to rule out all test's before giving up on fixing whatever has been missed.
troubleshooting performance issue for last 15 + years. Engine runs fine , no valve float. Just the power has never been restored. No shop or anyone would know anything is wrong with this engine. Even though a shop tore it right down 15+ years ago and put it back together from scratch - it has never ran how it did when i first bought this car. - no mechanic/ engine builder / shop has been able to truly say this reason a) or b) . They say ... let me build you another engine. dynamic compression coming soon
Are you sure you have the tune correct? With 190psi, you have to be careful about timing and detonation. How about camshaft or camshaft timing? What are the cam specs? AG
@@goldsgarage8236 Thanks again AG! 02 sensor installed while back, good idle and WOT safe #'s, plugs - light tan . Never heard detonation since owning it (1992). Realize doesn't mean it isn't happening. Initial timing 18/Mechanical 18. I do not know camshaft initial installed degree measurements (1992) as car was bought site unseen. A shop rebuilt it in 2000 when that cam went flat, same cam chosen-284h-crane degreed the 230/230 .480/.480 LSA 112 on ICL 107. Just a list of things changed last 20 years - distributors/carb's/springs/rockers/torque converter/ intake's. Dynamic idle #'s 110-130 psi / Snap 165-180 psi. Any other tests you might have let me know . I really don't see anything wrong with these #'s , I don't see anything happening with the heads to warrant them being pulled to inspect. It looks like rings are good? My only clue was cranking compression prior to rebuild was 165 , they shaved the heads .10 thou and cam was far advanced more than usual 4 degrees. I can only think of bringing cam to 112 ICL straight up or even 114 - 2+ retarded ? Maybe that magically restores the top end rush seat of pants back. Incidentally the pop up pistons in this engine have swirl marks on the top which could be casting swirls or hidden detonation? How would i even test that theory if somehow the pistons were the culprit.
@@goldsgarage8236 Oh hey, just wanted to circle back. Hope you had great trip. Thanks again for your help. I don't think there is a problem health wise engine as it relates to rings / heads. I think you would agree. From the internet. My only course of action is to run cam straight up with no advance and see what it does.
In the USA octane in the 60's I believe was motor octane and today it is an average of motor and research octane number (R+M/2). RON is tested on a special engine that can vary the compression ratio at idle and MON is tested on a special variable compression engine at higher loads and speeds. I think that I have read that many other countries at least once upon a time used only the MON rating which could be a different number than we use in the USA. I haven't thought about it in years so I don't know if that is still true since things are always changing. I'm not sure but I think race fuel in the USA is MON only.
Thanks for the education on fuel Gary and for supporting my channel. AG
Generally speaking, and negating the hundreds of other factors that effect engine power, will more timing with higher octane usually have more power ? As an example, if we had a typical 500 HP BBC street beast running great on 93 octane, with say a 10:1 CR, and 30* total timing, gain more power simply by changing to a 103 octane and bumping timing to say 36* ?
Thanks J. I believe that is true, although I have never tried it on the dyno. AG
@@goldsgarage8236 Thanks for the response. Great channel !
Thank you, great video. I am a new subscriber, and of course I have some questions. I think you are in Canada so maybe fuels are different than US but I was born in 1969 in Connecticut. Until around 1990 we had 87 unleaded, 93 unleaded and 89 leaded. After 1990 no more leaded but it remained 89 octane. We currently still have those three choices of unleaded. You talked about 1968 with high compression Motors. I guess there was no unleaded yet but regular was 87 octane leaded and what was the octane of the high-test leaded? And was there two or three choices of pump gas octane?
That 100 octane fuel you mentioned, was that race fuel or pump gas?
And today I see we're up to 12 and a half 1 compression again but with 87 octane and I guess that's due to direct injection?
Thanks for the question Not Me.
Sunoco had multiple choices, the highest was 260 with 100 octane right at the pump, not exactly sure of the other blends but I assume it was down to 87 or so.
You are correct about direct injection, as the piston is only compressing air until just before ignition.
Let me know if I answered your question and thanks for supporting my channel. AG
@@goldsgarage8236 well done, thanks for the answer. Yes I was confused because it seems like the name of the gas is 260 but the octane is 100. That was just slightly before my time so I missed out on that. But it must have been great to get 100 octane leaded fuel for pennies a gallon.
Thanks
Daryl
Florida
I would like some advice on cam selection. 5000 lb 4x4, ford 400cid engine, 10.8:1 static compression ratio, ELEVATION 6000 to 8000 feet, C6 auto transmission, 3.50 gears with 34" tires, TFS heads. Elevation totally messes up my cranking compression ratios. I would like a 170 to 180 psi cranking pressure at my elevation. What cam specifications should I be looking at? RPM range 2000 to 4500.
Thanks for the question rods. There are cams referred to as RV cams, lots of low end torque, so relatively low duration,
@@goldsgarage8236 dont alot of Fords already have 1.6 rockers?
you might consider advancing the cam......if you have the piston to valve clearance.
My main issue is elevation. I would like to have a camshaft that will make pressure at 7000 ft as if it were at sea level. 160 psi at sea level is only 128 psi up here. Off the shelf RV cams do not factor in elevations like I deal with.
@@rodshuffy4045 I would say advance the cam to close the intake valve sooner or call and get a custom grind.
What would be the purpose of making 12.5 compression and then bleeding it off.
Bleeding off is only effective at low RPM when the engine is vulnerable to detonation. At high RPM, the mass and intertia of the FA mixture fills the chamber. AG
I re-subscribed.
I had already subscribed before.
For what ever the reason I was not subscribed.
You have a good channel.
Take care, Ed.
Thanks Ed, I enjoy your comments. AG
My 09 cbr600RR is 12. 5 to 1 and running for 60k miles on 93 &94
Thanks for sharing your experience Craig AG