It's worth mentioning that your altitude where you live is also very important! I use the Wallace racing calculator and it has this included. And the cam timing number you need are the "off the seat" duration number and not the "at .050" number to select the most proper camshaft for the application. I live at 3400 above sea level, and I'm using Aluminum cylinder heads, so an 11.8 to one static compression is what I need to get 170 psi with the parts I have!...good to see professional builders sharing this priceless info!
Thank you for your time for making the educational videos. I think I may know one important reason why your viewers are not understanding dynamic compression ratios and cylinder pressures, most camshaft spec cards give the intake closing degree at .050" and not at .006", so the viewers are entering the camshaft duration numbers at .050" lift into the calculators and getting the IVC numbers at .050", when the viewers should be entering the camshaft "advertised" duration into the calculators to get the correct IVC number at .006" to use for calculating dynamic compression. Most of the online dynamic calculators ask for the camshaft duration at .050" spitting out the IVC number at .050", which again is the incorrect IVC number to use for calculating dynamic compression. In closing, the camshaft advertised duration is be used to calculate the correct IVC angle, which then is used for calculating dynamic compression.
Many videos talk about dynamic compression ratio and this is the first video I have watched that gives a good understanding of what it actually is without going on a search for a video on the topic. Many books also leave you in limbo. Thanks for posting this video as it makes understanding a camshaft a little less complex for most to be successful with their build.
Thanks Stovebolt, I am glad it was helpful. Comments like yours have inspired me to take a deeper dive into this subject and I will be making another video on the subject soon, possibly today. Watch for it. Allan Gold
It’s always in limbo because every engine is different. Their is no “set” numbers . That’s why all components need to be carefully chosen so they work together properly.
Thank you for including the story about getting it wrong. I have been fighting with my FE 390 rebuild with a new cam, but all stock for almost 8 months. I have tried everything, advancing cam, smaller carb, different tuning, etc. All stock motor except a cam I have now finally come to realize, is WAY too big for the compression ratio (Probably mid to high 8's, I have 120 flat in all cylinders on compression test). It just is nice to see that not everyone gets it right 100% of the time even pros, and really helps fix the hole in my pride over getting it wrong. Along with the tech info, I think I feel confident enough to get back out there and get it fixed.
Fantastic information!! Amazing the difference small changes make in engine power. I’m a life long Pontiac man and love how those old Indians make great torque!
I was lucky that I ended with 175psi of static compression when rebuilding my first engine with only guessing by picking parts around. But now that I'm rebuilding my second engine I want to take more time and measure things correctly and do the correct planning, videos like this are a gold mine of knowledge and encourage critical thinking before making decisions, thanks!
I really enjoy this channel. Alot of really good info you really don't hear anywhere else. Thank you for letting us follow along. When I clicked on the thumbnail I thought this channel had been around a while. Your very comfortable in front of the camera. Or so it seems lol. Thank you sir.
The past 3 motors I put together I did this, shooting for 7.75 to 8 to 1 dynamic with iron heads. They run excellent, so much better than tossing something together with low compression. The combo doesn't work right without doing this. Nice to see similar experiences. Valve lift is also important based on what your heads flow. And obviously what powerband you want the engine to have. Pointless to have a cam that makes power up to 7500 rpm in a stock 454 big block. If it's built for it that's different.
Yes and David Vizard has some great videos on his yt channel about LSA too, he also has formulas on how to calculate LSA as well. He pounds the table about LSA that these cam manufacturers are making the LSA way to wide leaving 60 to 80 HP and Torque on the table. But here's the deal with DV's claims, his findings are solid for WOT max power but not necessarily for average power, cruising or fuel economy if that is something one is looking for? Tight LSA cams have more overlap that isn't necessarily part throttle friendly and the bigger the dur @ .050" the worse. So keep this in mind before choosing the extra top end power you'll have by sacrificing some part throttle power.
@@itseithergonnaworkoritaint7852 I run a 107 LSA in my 355 and the mid range is awesome. But I agree, if you want cruising and mild, stick with stock LSA.
You are both making some good points. The ideal LSA depends on engine displacement and cylinder head flow, (port size, valve size etc.) The bigger the displacement on the same heads the tighter it can be. Cam companies typically limit LSA because of the adverse effect on vacuum, drivability at low speed etc. I build street engines not race engines so the priority is mid range torque, throttle response and drivability. On the dyno average torque and horsepower is more important than peak. Thank you both for your input.
@@goldsgarage8236 what would you say psi or dynamic compression should be for 87 octane? Absolutely everything I've found only talks about "pump gas" I assume 93 and I understand it depends on heads, chamber design, eliminating hot spots in the cambers, quinch and so on. It would be nice to know a general range. Currently building a 383 fun/daily driver. Afr 195 enforcer heads, compression in 9.3 to 9.5 range, 0.040 quinch. I haven't cc'ed the heads yet so just an educated guess with 18cc dish pistons. I've found 1 article in all of google that was an 87 build that I did the math on the parts used and should have been about 7.56 dynamic compression around 151psi or so. Any ideas?
Thanks Nashville. I think you should be ok with 87 octane and 151 PSI compression pressure. Even so, unless cost is a big issue, why not just use 91 anyway so you don't have to worry about it? Hope this helps. AG
I have had great success in the past running really high compression (12.5 to 1) in a 355 chevrolet and relatively short duration (242/246] at .050 on a 108 LSA. Dart iron eagle 215 heads and rpm airgap intake. Mid 6.60s in the eighth in a 3200lb car.
This is great! I was surprised to see you had 700 subscribers, I was expecting 100x that number. People will discover these videos soon enough. Thanks for sharing the knowledge
Very informative video, thanks! I have a 327 with the CompCam version of the GM 3896929 300HP cam. My cranking pressure is 160, it runs smooth as a smelt!
Good stuff!! Know what readers need esp younger ones? Comprehensive vids that give basic explanations/characterisitcs of intake and exhaust valve opening and closing points, what the mean, changes, etc. You know that choosing 2 different brands of say a 280 hft cam can behave differently. Especially when increasing cyl compression its so crucial toget it right...so you dont have a ping monster nor a soggy dog. Think we all would appreciate it DV touches on some of it but the hour plus vids its easy to get lost.
@@heshtesh you can always use a 400 block and get a 428 aftermarket crankshaft that fits in a 400 block and Chevy big block connecting rods, all balanced from Butler, all you need to do it block machining and put it together.
@@kevinmanning4880 Appreciate the info but i've already got a big dollar sbc pump gas stroker for the street and what you suggest will only start another bad habit lol! Read a funny comment the other day from a Pontiac owner " nowhere else can one spend so much money to get so little power as with a Pontiac" lol I could feel for the guy. No I think i'll try to keep it simple this time around.
@@heshtesh you haven't been associated with the correct kind of people. Have you heard of Big Chief? He beat everything in no preps, with a '70 GTO, I mean everything. There's a Canadian driving his 1965 GTO to drag week, he pulls a 9.77. Pulls a trailer behind the Goat from Dragstrip to Dragstrip.
Good point and yes it is important. I should have addressed that in the video as well. I will try to fit that discussion into a future video. Thanks. AG
Very good Tech. I have been talking about this same subject for years. Have to get the cylinder pressure up. Do that the Horsepower and Torque comes up. Taking advantage of your Low and Midlift flow numbers. Good topic. I just subscribed to your channel. Take care, Ed.
Thanks Ed. Your comments are inspiring more thoughts on the subject and so I am thinking of a follow up video about how the OEM's managed this in the early muscle cars. They were pretty smart. Watch for it. Allan Gold
Even more important is making sure the cam lift isn’t way more than the heads can flow at peak lift of the cam. That will harm power even more than compression. Your heads have a peak flow number at a certain lift. Beyond that valve lift it has a negative effect on flow which hurts power. So a bigger cam isn’t always better. I believe this should be figured out before determining your optimal compression
I run forged flat tops with small valve reliefs, 64 cc vortec heads and 15 thou shim gasket and it runs fantastic.. The amount of torque over the old 882 open chamber heads is crazy! Now I worry about the 700r4 trans lol!
I've read on a Pontiac forum that Crower 60916 does not come from the factory with 4 degrees advance ground into it,that they need to be degreed to get to a 108-109,and they need to be advanced 4degrees to get to 108-109
Thanks for your comment Rob, Initially I had to advance it 4 degrees to get to 108 centerline. This time I advanced it 4 more degrees to get to 104 centerline. The crank sprocket it now installed on the 8A keyway.
Great video! I am in the process of designing a building a 496 for my 70 Chevelle. The block is at the machine shop now and I have went all Eagle forged lower end with main studs. Little much but I want the option of putting it on the bottle in the future. This is just street motor with a 10.2:1 CR with a .025 compressed head gasket. I haven't nailed down what cam I am going to be running but your video is great! I am sure I will watch in a couple more times :) Looking forward to part 2.
Great video! One comment I have regarding intake closing point is that depending on the cam manufacturer they may list the actual valve closing event or the tappet closing event. The calculators dont specify which one to use. Comp is the only cam manufacturer that I know of that lists actual "valve" timing events, others list "tappet" timing, and others don't even specify which one they are listing. Do you have any insight on this?
I got a bit of problem with my build in that the quench distance is too large. So I need to take the block back and get it ”zero decked”. The cr is a very healthy 12.4:1 so the quench is probably needed..
@@goldsgarage8236 Yeah I think Ill have to modify the combustion chamber in that case so the CR doesnt get too high. My main thing Im wondering about atm is the issue with quench distance. Only reason to deck the block would be to get the quench tighter but Im not sure if its worth it. On one hand I have pistons with a shallow dish in them and only a 11mm band/ring going around the piston that could act on the quench. On the other hand I seem to be in the distance that one should never be (0.055-0.06") according to most opinion. The head gasket I have will compress to 0.043-0.049" and since my pistons are around 0.011 below the deck it gives that large quench distance. A "zero decking" seem like it could be good but I cant really tell if it is worth it. I guess another possible solution is to taper the chamber quench pad slightly in the hopes of relieving some of the potential for the non-optimal quench distance making it knock sensitive. On-going research =)
Magnus, I agree, minimizing quench is definitely good to do but it is expensive because it requires decking the block. It does allow more compression without detonation, however decking the block increases compression so it is kind of a double edged sword. I am building 2 400SBC's right now. One is .005" deck and the other block is untouched. I need 75cc heads to get the compression manageable in the decked block. Watch for them on the test stand and dyno.
@@goldsgarage8236 yeah. And its hard to take back a decked block to how it was 😄 My brother suggested Id draw up the gasket in cad and have it cur out in copper. But Im not sure how it would seal up the water in the long run. Common practice on race engines not so sure on street engines. Another benefit with that approach is I can reduce the crevice volume compared to the stock gasket wich have a 95mm hole compared to the 92.5mm bore on the engine.
Magnus. You can buy thicker head gaskets to reduce the compression but it kind of defeats the purpose of decking the block. Better to take it out of the heads or pistons if you can.
Love your video! Question, I have a stock factory 1996 chevy 5.7 vortec engine. I would like to change the pistons and add flat top pistons. I also want to run the LT4 Hotcam. I am trying to do this on a budget and keep it streetable. What do you recommend in maximum static compression for the Lt4 Hotcam. I will be using 1.6 roller rockers. Also will run headers with dual 2.5" pipes. The top of the engine will be ported vortec heads with machine work and springs and hardware to match cam. Also the intake will be factory with the spider injection upgraded to the improved system with injectors for each cylinder, rather than the poppets. Also the injectors will be 36lbs. Oh, also high flow performance fuel pump. I want to put this engine together right. I don't mind running 91 oct premium gas. Transmission will be whatever stall converter to maximize launching and sither 4:11 or 4:56. Gears. The truck is just a fun weekend ride to cruise around and hit the strip occasionally.
Thanks Richard. With this cam and steel heads i still think you should stay under 10:1 to be safe. The Summit CR calculator works ok. With that info I suggest you google the Wallace Dynamic CR calculator and determine your cranking pressure. Again, I suggest 180psi max. Hope this helps. AG
@@goldsgarage8236 what camshaft would you recommend in this setup I have , except bumping the compression to 10:5 to 11 to 1? And still have "decent" street manners, run on 91 premium fuel and no more than 3600 stall? Using the vortec heads I mentioned? I guess what I'm after is at least getting into the 400-450 plus ft-lbs torque territory. I don't mind having that "Chop" in the cam when idling. Like I mentioned in my earlier post, my truck is a fun truck for cruising around and occasional strip action. Its definitely not a work truck and it will rarely see the highway, except when traveling to the strip an hour away from home. I know there will be a handful of cams to choose, but just from your experience, what do you think?
I will do my best. The vehicle and how you are planning to drive it is important. Since you are using gears, (high ratio numerically) and a converter and you want to race it a bigger cam is warranted. Is it an S10 or full size truck? Also a bigger cam will allow you to use more static compression so aim for the high side of 180PSI. Something in the 280-285 degrees of advertised duration, 230-240 @.050". This cam will have a late IV closing point, 66-70 ABDC. As for lift, I am thinking about .550" max with the 1.6 rockers. If you know the flow numbers from your Vortex heads, that should be taken into consideration. Some heads actually have reduced flow at higher lift. You will need to machine your Vortex heads to accommodate this lift and there is a max so that is a factor also. Check this out thoroughly to avoid coil bind or valve guide to retainer interference. If you don't mind the chop, a shorter LSA, probably about 108 would be ideal. Most factory cams are 110 which is a bit of a compromise, you don't want any wider LSA. Richard, that is my input for what its worth. You can also call the cam company for their suggestion and get other opinions. Thanks for the question. AG
One comment is that with that 0.065 head gasket you had no quench action. That's not great for efficiency or power. With the 0.025 the quench is probably great as long as the piston isn't way down the bore. It's too tight if it's zero decked and you might touch the head. Probably 0.035-0.045 is a good place to be. Quench is gasket thickness plus how far down the bore the piston is at tdc.
Thanks for your comment Robert, and sorry that I just noticed it. You are correct about the .065" gasket. My mistake for not measuring it on the first build. I agree .035"-.045" is ideal and the higher the compression, the more important it is. AG
Question on using a dynamic compression calculator. Should I be using total duration figures, or duration @.050? Im working on coming up with a good static compression and camshaft combination for 93 octane.
.967 I .928 E and the Henry show is 14.5to 1 what it mean to work so well is with my head 540 oil into lifters wouldn't bleed down I lose hundred thousand lift You might say that's dumb But it's straight 50 oil in it. there I had a lift from my camshaft I'd run 9.06 et at 148 mph in the 1/4 With 50 weight oil in it it would run a 8.67 et at 167 mph
I have a question about an engine having a static compression of 11.5:1 and a dynamic compression of 7.5:1: will using the camshaft to bleed off this much compression create a lot of problematic heat in the cylinders?
Good question Sammy. No it will not. The late closing point of the intake valve just traps and compresses less fuel/air mixture at low RPM which reduces the DC and cranking pressure. At high RPM, the inertia of the F/A mixture helps to fill the chamber. Hope this helps. AG
My builder in 2019 scared me that I'd need to use E85 only in my daily 418 LS3. I've been using 92/93 octane with 11.9 SCR, 8.9 DCR, 220 cranking psi. Peak tq is only with 20* advance, though oem heads.
Thanks evcass69, it would be interesting to know if you could make as much torque with less CR and more advance. I have never seen 220 PSI in a street motor.
hi , great Vidoe watched with keen interest. trying to work if my cam is "good" for the street. So much info online its hard to work out.Ive a bbc 427 with a cam thats 230/236@50 on a 114 lsa. I did a dynamic compression test and hit an average of 160 psi plus. Is that decent for the street? For low end grunt and snappy throttle? My Intake valve closes quite late relative to other street cams ( mine closes 45 abdc , a comp cams 262xe closes 35 abdc.Is this a big difference. Any advice appreciated before I replace camshaft!!
Thanks for the question Camaro. I think you are using the @.050" numbers for IVCP to calculate your dynamic compression. You should be using the @.006" or the advertised duration numbers. Nothing is being compressed until the valve is completely closed. The cam spec's are ok but i don't know enough about the application, static CR, gearing, weight of the car etc. Recalculate your DCR and let me know. Hope this helps. AG
Hi apolgies for the confusion , yes numbers are all at 50.I meant to write cranking compression not dynamic - as your video here is all about cranking compression pressure. So Im cranking avg 160psi - Im a bit concerned current cam too big for street use , but does they psi indicate its ok? wanting lots of low rpm torque acceleration etc , not so much high HP high rpm use. @@goldsgarage8236
We all get that one should know static and dynamic compression ratios of their engine. But you fell flat when matching a cam to a compression ratio. Or maybe that was in part 2 which I can't find.
Thanks for the input. You are correct, the follow up video thumbnail is Quadrajet tuning. I think March 26. I describe the changes and results. I hope you are able t find it. AG
Help me understand please. If I have an engine with a rocker arm ratio of 1.5 and a valve spring with an open pressure of 300lbs. Does this mean the pounds of pressure needed at the cam would be 450lbs Since there is NO mechanical advantage upon opening the valve?
You are correct. Take moments about the pivot point. X x 1=300 x 1.5, therefore X=450. So the greater your rocker arm ratio, the more force you are putting between the valve lifter and cam. Hope this helps. AG
@@goldsgarage8236 Thx for the response. Now, assuming I replaced the 1.5 for 1.6 ration rockers and I adjust the geometry to achieve the same amount of lift. Would the pounds of pressure at the cam degrease or increase? I think the pressure would be 480lbs, thus an increase.
@@goldsgarage8236 Good catch. I mixed the terminology. This clearly proves why the OHC engines can outrev the OHV rivals. The emence pressure on the cam from the high pressure valve springs means a larger mass is needed for durability. Thus limiting RPM. I wish there were a way to bridge this gap. Would it be nice to have the best of both worlds.
Iv found .024 thou. Differance from 2 differant manufacturers 1.6 rockers with same, proper push rods on same engine.same day. The best ones opened the valves an honest .024 thou. More also remember, you may need to retard your cam a few degrees going from 1.5 to 1.6, because it acting like its advancing your cam by opening the valve sooner. There is a lot to learn about engine building.Hope this helps.
Thanks Ron. This is an interesting subject and I am planning to do some more research on it for a future video. To answer your question I referred to the 1968 Chevrolet manual. A 307 200HP engine (base engine that would require only "regular gas") had a cranking pressure of 150PSI. As always, other factors such as timing advance, spark plug heat range, fuel air ratio, driving style etc. could influence this as well. I hope this helps and watch for more info in this subject.
It’s a very interesting subject! Unfortunately octane and it’s function is a very misunderstood subject. In my opinion, octane and a proper timing curve are the two most important parts of a properly functioning engine no matter the usage from racing to towing the race car. Looking forward to more of your videos.
Thanks again Ron. This discussion inspired my next video. Would you believe that a 12.5:1 CR L88 427 has the same cranking pressure as the 307? I will explain why and how. Look for it soon.
Your 160/180psi is probably a good number for pump gas, 87 octane? I have a 400SB with about 170/180 psi runs on 87 just fine. But my question is going to 91 octane how much more psi can I go? 200/210psi? I don't like leaving power on the table.
All I have is the Intake Closing point at .050 lift cam specs. The calculators I see use the .006 lifter specs. Is there a conversion factor for this or call Lunati for those specs?
Thanks for the question. I think you should call. Some cams lift off the seat much quicker than others so I don't think there is any conversion factor. It's interesting that some flat tappet cams lift the valve off the seat quicker than roller cams.
The lobe ramp rate will control the delta between advertised IVC & 0.050 IVC. Using AIVC for DCR is best. Maybe you can get the AIVC from the vendor that ground the cam?
Can anyone answer why some calculators ask for the intake closing +15 degrees? United Engine Machine in particular. Wallace Racing Calculator doesn't ask but their calculations match my "actual" cranking pressure.
@@goldsgarage8236 Thanks for replying. I've decided to only use the Wallace calculator. One question. When figuring cranking compression, should I use "advertised" intake closing and not .050? Thanks again.
I wound eventually like to increase my TQ n HP on my stock 95 gen 2 5.7 LT1 engine a few hundred ponies more to the rear wheels without blowing her up hmmmmmmmm what to do ?????
Thanks Mark, Please keep watching my channel and hopefully you will find some of the info you are looking for. i have a 400SBC build coming up next. AG
Compression adds power everywhere in power curve! What people need to decide is what kind of fuel to run and what kind of octane they want to use! If they want to run 87 octane 9 to 1 is all I would push with todays crap 87 octane!
😂 me dieing inside because I have 250 psi and I run 93 with two stroke racing oil pistons are.003 out of the hole and a .035 with fire ring gasket. 230 24 something 107 or 106 intake centerline and 114 lsa .54 lift 6in forged rods. steel crank. bracket racing keath black flat tops 7cc valve releaf she pulls hard to 7000k 😂 and has managed to break everything behind the flywheel it all started with the damn 454 clutch snap that b**** into a million bits. Twisted a drive shaft in half then snap the pinion gear shaft after it was all said and done with chromoly everything in the rear end I cracked the f****** housing now I have a little Dana 80 and i have put the project on hold because it eat all the hp but I put so much effort in making it fit i don't want to take it out so I'm thinking she will be a mud truck now but I have 3.55 gears and just kinda lost interest in it
That cam is weak in the knees on the lift side of things....You wanna build some cyl pressure, put that cam on a 108 LSA instead of taking a 112 then advancing it 8 dgrees....Save the 112 lsa crap for large bbc...or LS. A tighter LSA will kick the pants off that 112 dual pattern, any day of the week.. If vacuum is all your concerned about, then don't be disappointed when the dyno falls short...jmtc
It's worth mentioning that your altitude where you live is also very important! I use the Wallace racing calculator and it has this included.
And the cam timing number you need are the "off the seat" duration number and not the "at .050" number to select the most proper camshaft for the application.
I live at 3400 above sea level, and I'm using Aluminum cylinder heads, so an 11.8 to one static compression is what I need to get 170 psi with the parts I have!...good to see professional builders sharing this priceless info!
Thanks for your valued information and comments Duane
Us car guys need more real world videos like this! Thank you for sharing.
Thanks for your kind words Robert, it motivates me to keep making videos.
Allan Gold
Thank you for your time for making the educational videos. I think I may know one important reason why your viewers are not understanding dynamic compression ratios and cylinder pressures, most camshaft spec cards give the intake closing degree at .050" and not at .006", so the viewers are entering the camshaft duration numbers at .050" lift into the calculators and getting the IVC numbers at .050", when the viewers should be entering the camshaft "advertised" duration into the calculators to get the correct IVC number at .006" to use for calculating dynamic compression.
Most of the online dynamic calculators ask for the camshaft duration at .050" spitting out the IVC number at .050", which again is the incorrect IVC number to use for calculating dynamic compression.
In closing, the camshaft advertised duration is be used to calculate the correct IVC angle, which then is used for calculating dynamic compression.
Correct Sammy. Nothing is being compressed (at low RPM) until the intake valve is completely closed. Thanks for commenting. AG
Many videos talk about dynamic compression ratio and this is the first video I have watched that gives a good understanding of what it actually is without going on a search for a video on the topic. Many books also leave you in limbo. Thanks for posting this video as it makes understanding a camshaft a little less complex for most to be successful with their build.
Thanks Stovebolt, I am glad it was helpful. Comments like yours have inspired me to take a deeper dive into this subject and I will be making another video on the subject soon, possibly today. Watch for it. Allan Gold
It’s always in limbo because every engine is different. Their is no “set” numbers . That’s why all components need to be carefully chosen so they work together properly.
Thank you for including the story about getting it wrong. I have been fighting with my FE 390 rebuild with a new cam, but all stock for almost 8 months. I have tried everything, advancing cam, smaller carb, different tuning, etc. All stock motor except a cam I have now finally come to realize, is WAY too big for the compression ratio (Probably mid to high 8's, I have 120 flat in all cylinders on compression test).
It just is nice to see that not everyone gets it right 100% of the time even pros, and really helps fix the hole in my pride over getting it wrong. Along with the tech info, I think I feel confident enough to get back out there and get it fixed.
Good information hunter, thanks for commenting. Experience is expensive! AG
Fantastic information!! Amazing the difference small changes make in engine power. I’m a life long Pontiac man and love how those old Indians make great torque!
Thanks L, they are a beautiful piece of history and fun to work on. Thanks for watching Gold's Garage. AG
I was lucky that I ended with 175psi of static compression when rebuilding my first engine with only guessing by picking parts around.
But now that I'm rebuilding my second engine I want to take more time and measure things correctly and do the correct planning, videos like this are a gold mine of knowledge and encourage critical thinking before making decisions, thanks!
Very nice compliment, thanks. AG
I really enjoy this channel. Alot of really good info you really don't hear anywhere else. Thank you for letting us follow along. When I clicked on the thumbnail I thought this channel had been around a while. Your very comfortable in front of the camera. Or so it seems lol. Thank you sir.
Thanks for your kind words Hugh. It motivates me to keep digging!
Please keep watching and commenting!
Allan Gold
The past 3 motors I put together I did this, shooting for 7.75 to 8 to 1 dynamic with iron heads. They run excellent, so much better than tossing something together with low compression. The combo doesn't work right without doing this. Nice to see similar experiences. Valve lift is also important based on what your heads flow. And obviously what powerband you want the engine to have. Pointless to have a cam that makes power up to 7500 rpm in a stock 454 big block. If it's built for it that's different.
Thanks CK, all good points, thanks for your input. AG
A tight LSA will trap more compression, something in the range of 106 - 108. Also I use .015 steel shim gaskets with cast iron heads.
Yes and David Vizard has some great videos on his yt channel about LSA too, he also has formulas on how to calculate LSA as well. He pounds the table about LSA that these cam manufacturers are making the LSA way to wide leaving 60 to 80 HP and Torque on the table.
But here's the deal with DV's claims, his findings are solid for WOT max power but not necessarily for average power, cruising or fuel economy if that is something one is looking for? Tight LSA cams have more overlap that isn't necessarily part throttle friendly and the bigger the dur @ .050" the worse. So keep this in mind before choosing the extra top end power you'll have by sacrificing some part throttle power.
@@itseithergonnaworkoritaint7852 I run a 107 LSA in my 355 and the mid range is awesome. But I agree, if you want cruising and mild, stick with stock LSA.
You are both making some good points. The ideal LSA depends on engine displacement and cylinder head flow, (port size, valve size etc.) The bigger the displacement on the same heads the tighter it can be. Cam companies typically limit LSA because of the adverse effect on vacuum, drivability at low speed etc. I build street engines not race engines so the priority is mid range torque, throttle response and drivability. On the dyno average torque and horsepower is more important than peak. Thank you both for your input.
@@goldsgarage8236 what would you say psi or dynamic compression should be for 87 octane? Absolutely everything I've found only talks about "pump gas" I assume 93 and I understand it depends on heads, chamber design, eliminating hot spots in the cambers, quinch and so on. It would be nice to know a general range. Currently building a 383 fun/daily driver. Afr 195 enforcer heads, compression in 9.3 to 9.5 range, 0.040 quinch. I haven't cc'ed the heads yet so just an educated guess with 18cc dish pistons. I've found 1 article in all of google that was an 87 build that I did the math on the parts used and should have been about 7.56 dynamic compression around 151psi or so. Any ideas?
Thanks Nashville.
I think you should be ok with 87 octane and 151 PSI compression pressure. Even so, unless cost is a big issue, why not just use 91 anyway so you don't have to worry about it? Hope this helps. AG
I have had great success in the past running really high compression (12.5 to 1) in a 355 chevrolet and relatively short duration (242/246] at .050 on a 108 LSA. Dart iron eagle 215 heads and rpm airgap intake. Mid 6.60s in the eighth in a 3200lb car.
Mid 6.60's is pretty fast. That would be low 10's in the quarter. I had a chance to drive a 6.60 drag car a few years ago. It was pretty exciting. AG
What is the intake centerline angle
This is great! I was surprised to see you had 700 subscribers, I was expecting 100x that number. People will discover these videos soon enough. Thanks for sharing the knowledge
same here! totally clicked on this thinking it was a shop with a decent following. theyll get there!
Thanks for your nice comments Leo. It encourages me to keep digging. I have a lot of content in the pipeline so please watch for it. Thanks again!
Thanks for your comment soup!
Thanks for your kind words Leo. You are encouraging me to keep building engines and making videos. More to come.
Nicely done ,very informative
Interesting-really like the preplanning advice-
Thanks Alex, always appreciate your input. Are you coming to the dyno test next Saturday?
Very informative video, thanks! I have a 327 with the CompCam version of the GM 3896929 300HP cam. My cranking pressure is 160, it runs smooth as a smelt!
Sounds like a very nice street engine John, Thanks for your input. AG
Just curious, do you know pretty accurately what your static compression is?
@@mikewillett5076 It was 160psi last I checked.
Good stuff!!
Know what readers need esp younger ones?
Comprehensive vids that give basic explanations/characterisitcs of intake and exhaust valve opening and closing points, what the mean, changes, etc.
You know that choosing 2 different brands of say a 280 hft cam can behave differently. Especially when increasing cyl compression its so crucial toget it right...so you dont have a ping monster nor a soggy dog.
Think we all would appreciate it
DV touches on some of it but the hour plus vids its easy to get lost.
Thanks Gord, i have other videos on this subject. More to come. AG
Oh do I like this topic! Off to work but I'll return with my experiences with on this topic soon.
Thanks Bobby. I always appreciate your input. AG
I use an NOS Edelbrock perforiert Plus 2102 cam in My smallblock L48 engine with 9.7:1 compression that works nicely
Valuable information! Thank you so much for doing this video! I'm planning on putting together an aftermarket top end on a Pontiac 428.
Thanks Kevin, glad it was helpful.
I'm trying to pry a 69 428 from a friend for a 72 Gran Prix, still has the original factory headers.
@@heshtesh you can always use a 400 block and get a 428 aftermarket crankshaft that fits in a 400 block and Chevy big block connecting rods, all balanced from Butler, all you need to do it block machining and put it together.
@@kevinmanning4880 Appreciate the info but i've already got a big dollar sbc pump gas stroker for the street and what you suggest will only start another bad habit lol! Read a funny comment the other day from a Pontiac owner " nowhere else can one spend so much money to get so little power as with a Pontiac" lol I could feel for the guy. No I think i'll try to keep it simple this time around.
@@heshtesh you haven't been associated with the correct kind of people. Have you heard of Big Chief? He beat everything in no preps, with a '70 GTO, I mean everything. There's a Canadian driving his 1965 GTO to drag week, he pulls a 9.77. Pulls a trailer behind the Goat from Dragstrip to Dragstrip.
You can't forget the LSA that is very important.what is happening to start the intake stroke,a lot of people miss that.
Good point and yes it is important. I should have addressed that in the video as well. I will try to fit that discussion into a future video. Thanks. AG
Very good Tech.
I have been talking about this same subject for years.
Have to get the cylinder pressure up.
Do that the Horsepower and Torque comes up.
Taking advantage of your Low and Midlift flow numbers.
Good topic.
I just subscribed to your channel.
Take care, Ed.
Thanks Ed. Your comments are inspiring more thoughts on the subject and so I am thinking of a follow up video about how the OEM's managed this in the early muscle cars. They were pretty smart. Watch for it.
Allan Gold
@@goldsgarage8236Thanks Allan, I'll be watching for your video.
Great topic.
Thanks again, Ed.
Pure Gold, thank you brother, your much appreciated!
Even more important is making sure the cam lift isn’t way more than the heads can flow at peak lift of the cam. That will harm power even more than compression. Your heads have a peak flow number at a certain lift. Beyond that valve lift it has a negative effect on flow which hurts power. So a bigger cam isn’t always better. I believe this should be figured out before determining your optimal compression
you are correct, good point. Thanks Chris. AG
I always check for run out on a new crankshaft. Many have been sent back as they were bent.
Good advice, thanks Steven. AG
That was fantastic, thanks for the video.
Thanks for your kind words John, lots of content to come. AG
cant wait for part 2. thank you.
Thanks Andrew, we are excited to see the results also.
David Visard. Tested. Wisdom by experience.
Thanks Julian. AG
Great way of present things
Thanks for your kind words Remy, I encourages me to make more videos.
Allan Gold
I run forged flat tops with small valve reliefs, 64 cc vortec heads and 15 thou shim gasket and it runs fantastic.. The amount of torque over the old 882 open chamber heads is crazy! Now I worry about the 700r4 trans lol!
Thanks Larry, what is your CR and what are you using for a cam?
Gotta love those Vortecs!
Very interesting and helpful, deletes a lot of guess work and saves💲
Thanks Jim, exactly what I am trying to do so your comment reinforces that I am on a good path. Ag
I've read on a Pontiac forum that Crower 60916 does not come from the factory with 4 degrees advance ground into it,that they need to be degreed to get to a 108-109,and they need to be advanced 4degrees to get to 108-109
Thanks for your comment Rob, Initially I had to advance it 4 degrees to get to 108 centerline. This time I advanced it 4 more degrees to get to 104 centerline. The crank sprocket it now installed on the 8A keyway.
Great video! I am in the process of designing a building a 496 for my 70 Chevelle. The block is at the machine shop now and I have went all Eagle forged lower end with main studs. Little much but I want the option of putting it on the bottle in the future. This is just street motor with a 10.2:1 CR with a .025 compressed head gasket. I haven't nailed down what cam I am going to be running but your video is great! I am sure I will watch in a couple more times :) Looking forward to part 2.
Thanks for your input shanman. I apologize that I just noticed it now. AG
Great video! One comment I have regarding intake closing point is that depending on the cam manufacturer they may list the actual valve closing event or the tappet closing event.
The calculators dont specify which one to use. Comp is the only cam manufacturer that I know of that lists actual "valve" timing events, others list "tappet" timing, and others don't even specify which one they are listing. Do you have any insight on this?
Thanks for the info! AG
Very thorough...
Thanks John, glad you are enjoying my videos. AG
I got a bit of problem with my build in that the quench distance is too large.
So I need to take the block back and get it ”zero decked”.
The cr is a very healthy 12.4:1 so the quench is probably needed..
Thanks Magnus, I would suggest you re-calculate your CR after to deck the block.
@@goldsgarage8236 Yeah I think Ill have to modify the combustion chamber in that case so the CR doesnt get too high.
My main thing Im wondering about atm is the issue with quench distance. Only reason to deck the block would be to get the quench tighter but Im not sure if its worth it.
On one hand I have pistons with a shallow dish in them and only a 11mm band/ring going around the piston that could act on the quench.
On the other hand I seem to be in the distance that one should never be (0.055-0.06") according to most opinion.
The head gasket I have will compress to 0.043-0.049" and since my pistons are around 0.011 below the deck it gives that large quench distance.
A "zero decking" seem like it could be good but I cant really tell if it is worth it.
I guess another possible solution is to taper the chamber quench pad slightly in the hopes of relieving some of the potential for the non-optimal quench distance making it knock sensitive.
On-going research =)
Magnus, I agree, minimizing quench is definitely good to do but it is expensive because it requires decking the block. It does allow more compression without detonation, however decking the block increases compression so it is kind of a double edged sword. I am building 2 400SBC's right now. One is .005" deck and the other block is untouched. I need 75cc heads to get the compression manageable in the decked block. Watch for them on the test stand and dyno.
@@goldsgarage8236 yeah. And its hard to take back a decked block to how it was 😄
My brother suggested Id draw up the gasket in cad and have it cur out in copper. But Im not sure how it would seal up the water in the long run. Common practice on race engines not so sure on street engines.
Another benefit with that approach is I can reduce the crevice volume compared to the stock gasket wich have a 95mm hole compared to the 92.5mm bore on the engine.
Magnus. You can buy thicker head gaskets to reduce the compression but it kind of defeats the purpose of decking the block. Better to take it out of the heads or pistons if you can.
Love your video! Question, I have a stock factory 1996 chevy 5.7 vortec engine. I would like to change the pistons and add flat top pistons. I also want to run the LT4 Hotcam. I am trying to do this on a budget and keep it streetable. What do you recommend in maximum static compression for the Lt4 Hotcam. I will be using 1.6 roller rockers. Also will run headers with dual 2.5" pipes. The top of the engine will be ported vortec heads with machine work and springs and hardware to match cam. Also the intake will be factory with the spider injection upgraded to the improved system with injectors for each cylinder, rather than the poppets. Also the injectors will be 36lbs. Oh, also high flow performance fuel pump. I want to put this engine together right. I don't mind running 91 oct premium gas. Transmission will be whatever stall converter to maximize launching and sither 4:11 or 4:56. Gears. The truck is just a fun weekend ride to cruise around and hit the strip occasionally.
Thanks Richard. With this cam and steel heads i still think you should stay under 10:1 to be safe. The Summit CR calculator works ok. With that info I suggest you google the Wallace Dynamic CR calculator and determine your cranking pressure. Again, I suggest 180psi max. Hope this helps. AG
@@goldsgarage8236 what camshaft would you recommend in this setup I have , except bumping the compression to 10:5 to 11 to 1? And still have "decent" street manners, run on 91 premium fuel and no more than 3600 stall? Using the vortec heads I mentioned? I guess what I'm after is at least getting into the 400-450 plus ft-lbs torque territory. I don't mind having that "Chop" in the cam when idling. Like I mentioned in my earlier post, my truck is a fun truck for cruising around and occasional strip action. Its definitely not a work truck and it will rarely see the highway, except when traveling to the strip an hour away from home. I know there will be a handful of cams to choose, but just from your experience, what do you think?
I will do my best. The vehicle and how you are planning to drive it is important. Since you are using gears, (high ratio numerically) and a converter and you want to race it a bigger cam is warranted. Is it an S10 or full size truck?
Also a bigger cam will allow you to use more static compression so aim for the high side of 180PSI. Something in the 280-285 degrees of advertised duration, 230-240 @.050". This cam will have a late IV closing point, 66-70 ABDC. As for lift, I am thinking about .550" max with the 1.6 rockers. If you know the flow numbers from your Vortex heads, that should be taken into consideration. Some heads actually have reduced flow at higher lift.
You will need to machine your Vortex heads to accommodate this lift and there is a max so that is a factor also. Check this out thoroughly to avoid coil bind or valve guide to retainer interference.
If you don't mind the chop, a shorter LSA, probably about 108 would be ideal.
Most factory cams are 110 which is a bit of a compromise, you don't want any wider LSA.
Richard, that is my input for what its worth. You can also call the cam company for their suggestion and get other opinions.
Thanks for the question. AG
One comment is that with that 0.065 head gasket you had no quench action. That's not great for efficiency or power. With the 0.025 the quench is probably great as long as the piston isn't way down the bore. It's too tight if it's zero decked and you might touch the head. Probably 0.035-0.045 is a good place to be. Quench is gasket thickness plus how far down the bore the piston is at tdc.
Thanks for your comment Robert, and sorry that I just noticed it. You are correct about the .065" gasket. My mistake for not measuring it on the first build. I agree .035"-.045" is ideal and the higher the compression, the more important it is. AG
What flowmaster muffler is that ? Sounds great.
Sorry Kevin, what video are you referring to in your question? AG
Question on using a dynamic compression calculator. Should I be using total duration figures, or duration @.050? Im working on coming up with a good static compression and camshaft combination for 93 octane.
Good question Noble. Always use advertised duration, not duration @.050" AG
.967 I .928 E and the Henry show is 14.5to 1 what it mean to work so well is with my head 540 oil into lifters wouldn't bleed down I lose hundred thousand lift
You might say that's dumb
But it's straight 50 oil in it. there I had a lift from my camshaft
I'd run 9.06 et at 148 mph in the 1/4
With 50 weight oil in it it would run a 8.67 et at 167 mph
Thanks for your input Scott.
Rhoads hydraulic lifters will also trap compression and you want to run with a deck clearance no less or more than .035
Thanks Jarrett. AG
I have a question about an engine having a static compression of 11.5:1 and a dynamic compression of 7.5:1: will using the camshaft to bleed off this much compression create a lot of problematic heat in the cylinders?
Good question Sammy. No it will not. The late closing point of the intake valve just traps and compresses less fuel/air mixture at low RPM which reduces the DC and cranking pressure. At high RPM, the inertia of the F/A mixture helps to fill the chamber. Hope this helps. AG
My builder in 2019 scared me that I'd need to use E85 only in my daily 418 LS3. I've been using 92/93 octane with 11.9 SCR, 8.9 DCR, 220 cranking psi. Peak tq is only with 20* advance, though oem heads.
Thanks evcass69, it would be interesting to know if you could make as much torque with less CR and more advance. I have never seen 220 PSI in a street motor.
@@goldsgarage8236 I wonder also.
hi , great Vidoe watched with keen interest. trying to work if my cam is "good" for the street. So much info online its hard to work out.Ive a bbc 427 with a cam thats 230/236@50 on a 114 lsa. I did a dynamic compression test and hit an average of 160 psi plus. Is that decent for the street? For low end grunt and snappy throttle? My Intake valve closes quite late relative to other street cams ( mine closes 45 abdc , a comp cams 262xe closes 35 abdc.Is this a big difference. Any advice appreciated before I replace camshaft!!
Thanks for the question Camaro. I think you are using the @.050" numbers for IVCP to calculate your dynamic compression. You should be using the @.006" or the advertised duration numbers. Nothing is being compressed until the valve is completely closed. The cam spec's are ok but i don't know enough about the application, static CR, gearing, weight of the car etc. Recalculate your DCR and let me know. Hope this helps. AG
Hi apolgies for the confusion , yes numbers are all at 50.I meant to write cranking compression not dynamic - as your video here is all about cranking compression pressure. So Im cranking avg 160psi - Im a bit concerned current cam too big for street use , but does they psi indicate its ok? wanting lots of low rpm torque acceleration etc , not so much high HP high rpm use. @@goldsgarage8236
The major problem is none of the cam grinders advertise the actual degs ATDC when the intake touches the seat. .006 is not good enough.
Thanks for your input Racer.
We all get that one should know static and dynamic compression ratios of their engine. But you fell flat when matching a cam to a compression ratio. Or maybe that was in part 2 which I can't find.
Thanks for the input. You are correct, the follow up video thumbnail is Quadrajet tuning. I think March 26. I describe the changes and results. I hope you are able t find it. AG
Help me understand please. If I have an engine with a rocker arm ratio of 1.5 and a valve spring with an open pressure of 300lbs. Does this mean the pounds of pressure needed at the cam would be 450lbs Since there is NO mechanical advantage upon opening the valve?
You are correct. Take moments about the pivot point. X x 1=300 x 1.5, therefore X=450. So the greater your rocker arm ratio, the more force you are putting between the valve lifter and cam. Hope this helps. AG
@@goldsgarage8236 Thx for the response. Now, assuming I replaced the 1.5 for 1.6 ration rockers and I adjust the geometry to achieve the same amount of lift. Would the pounds of pressure at the cam degrease or increase? I think the pressure would be 480lbs, thus an increase.
If you replace the 1.5 with 1.6 rockers, you will have 480 lb. force (not pressure) on the cam and lifter. AG
@@goldsgarage8236 Good catch. I mixed the terminology. This clearly proves why the OHC engines can outrev the OHV rivals. The emence pressure on the cam from the high pressure valve springs means a larger mass is needed for durability. Thus limiting RPM. I wish there were a way to bridge this gap. Would it be nice to have the best of both worlds.
Iv found .024 thou. Differance from 2 differant manufacturers 1.6 rockers with same, proper push rods on same engine.same day. The best ones opened the valves an honest .024 thou. More also remember, you may need to retard your cam a few degrees going from 1.5 to 1.6, because it acting like its advancing your cam by opening the valve sooner. There is a lot to learn about engine building.Hope this helps.
Thanks for the info Peggy. We are always learning.AG
I am very serious about you Building a 350 Chevy Engine for me.
I’m going to assume 160 to 180 is a target for premium pump fuel? What cylinder pressure would one want for running 87 octane fuel?
Thanks Ron. This is an interesting subject and I am planning to do some more research on it for a future video. To answer your question I referred to the 1968 Chevrolet manual. A 307 200HP engine (base engine that would require only "regular gas") had a cranking pressure of 150PSI. As always, other factors such as timing advance, spark plug heat range, fuel air ratio, driving style etc. could influence this as well.
I hope this helps and watch for more info in this subject.
It’s a very interesting subject! Unfortunately octane and it’s function is a very misunderstood subject. In my opinion, octane and a proper timing curve are the two most important parts of a properly functioning engine no matter the usage from racing to towing the race car. Looking forward to more of your videos.
Thanks again Ron. This discussion inspired my next video. Would you believe that a 12.5:1 CR L88 427 has the same cranking pressure as the 307? I will explain why and how. Look for it soon.
Your 160/180psi is probably a good number for pump gas, 87 octane? I have a 400SB with about 170/180 psi runs on 87 just fine. But my question is going to 91 octane how much more psi can I go? 200/210psi? I don't like leaving power on the table.
Thanks Jesse, i am planning to discuss this issue in my follow up video. Thanks for supporting my channel. AG
@@goldsgarage8236 yes and yes. Can't wait to watch it.
How does this change with adding boost?
Thanks for the question. I am sorry, i don't have any experience with boost. Maybe another viewer can weigh in on this question. AG
All I have is the Intake Closing point at .050 lift cam specs. The calculators I see use the .006 lifter specs. Is there a conversion factor for this or call Lunati for those specs?
Thanks for the question. I think you should call. Some cams lift off the seat much quicker than others so I don't think there is any conversion factor. It's interesting that some flat tappet cams lift the valve off the seat quicker than roller cams.
The lobe ramp rate will control the delta between advertised IVC & 0.050 IVC. Using AIVC for DCR is best. Maybe you can get the AIVC from the vendor that ground the cam?
Thanks evcass69, I always use advertised intake valve closing specs for my dynamic compression ratio calculations with good results.
Can anyone answer why some calculators ask for the intake closing +15 degrees? United Engine Machine in particular. Wallace Racing Calculator doesn't ask but their calculations match my "actual" cranking pressure.
Thanks Ragingbull340, I am getting good results with the Wallace calculator and advertised specs.
@@goldsgarage8236 Thanks for replying. I've decided to only use the Wallace calculator. One question. When figuring cranking compression, should I use "advertised" intake closing and not .050? Thanks again.
I wound eventually like to increase my TQ n HP on my stock 95 gen 2 5.7 LT1 engine a few hundred ponies more to the rear wheels without blowing her up hmmmmmmmm what to do ?????
Thanks Mark, Please keep watching my channel and hopefully you will find some of the info you are looking for. i have a 400SBC build coming up next. AG
Compression adds power everywhere in power curve! What people need to decide is what kind of fuel to run and what kind of octane they want to use! If they want to run 87 octane 9 to 1 is all I would push with todays crap 87 octane!
Thanks Larry, I agree. The dynamic compression should also be calculated as the cam can bleed off some of the cranking pressure.
Why not just use 10 to 1 compression.
Thanks for the comment James. AG
😂 me dieing inside because I have 250 psi and I run 93 with two stroke racing oil pistons are.003 out of the hole and a .035 with fire ring gasket. 230 24 something 107 or 106 intake centerline and 114 lsa .54 lift 6in forged rods. steel crank. bracket racing keath black flat tops 7cc valve releaf she pulls hard to 7000k 😂 and has managed to break everything behind the flywheel it all started with the damn 454 clutch snap that b**** into a million bits. Twisted a drive shaft in half then snap the pinion gear shaft after it was all said and done with chromoly everything in the rear end I cracked the f****** housing now I have a little Dana 80 and i have put the project on hold because it eat all the hp but I put so much effort in making it fit i don't want to take it out so I'm thinking she will be a mud truck now but I have 3.55 gears and just kinda lost interest in it
Thanks for the info Bart. AG
how about getting to the point
You don't even know what he is talking about
That cam is weak in the knees on the lift side of things....You wanna build some cyl pressure, put that cam on a 108 LSA instead of taking a 112 then advancing it 8 dgrees....Save the 112 lsa crap for large bbc...or LS. A tighter LSA will kick the pants off that 112 dual pattern, any day of the week.. If vacuum is all your concerned about, then don't be disappointed when the dyno falls short...jmtc
Thanks for the info Steve. AG
Sorry 9.5 compression is still to low. If you're a real man you should at lease run 10.5 even on a street motor
Real men run twin turbos at 8.5
What can I say Wave?
@@goldsgarage8236 🤣🤣🤣🤣