Cam profile dynamics Vs event BS bashing!
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- เผยแพร่เมื่อ 11 ก.ย. 2022
- In this, episode 70 part 2, DV goes for the throat on those consult guys and a few other pro's who are apparently spreading some pretty misleading info on cams. This is the second part of a focused BS attack on cam profiles and event timing that need to be straightened up. No holds barred here!
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This reminds me of a quote: "One accurate measurement is worth a thousand expert opinions."
COMP Cams' Billy Godbold
th-cam.com/video/1jPxdfPdhdU/w-d-xo.html
th-cam.com/video/NB-dbpVCOuo/w-d-xo.html
www.motortrend.com/how-to/ctrp- ... -dynamics/
Professor Blair and Associates
www.profblairandassociates.com/p ... 20Lift.pdf
www.profblairandassociates.com/p ... ration.pdf
www.amazon.com/Design-Simulatio ... 0768004403
www.profblairandassociates.com/G ... n_gpb.html
Thank you for this piece David, it’s nice to know that I’m not the only old fart that’s got into a (ahem) spirited discussion twixt “professional theoretician” and hands-on engineer with absolute knowledge built through decades of practical research and measurement.
I was an avid reader of anything and everything I could lay my hands on regarding race engine building from about age 12, when I built my first kart engine. I’m now in my 60’s so you’ve got 20 odd years on me.
I went the motorcycle route once I reached 16, paid my way through technical college by doing port work and builds for the local heroes. They kept turning up so I guess they were happy with the results. Lol.
In my 20’s I got seriously cheesed off with doing R&D work at an exhaust manufacturer’s factory so I set up on my own.
With a dyno, gas analyser, enquiring mind and a healthy dose of enthusiasm, in the first 6 years we nailed 11 British Championship titles plus I have no idea how many LR’s, race wins and podiums, club titles etc. using the same empirical testing methodology as yourself.
Then I went World Championship racing. What I hadn’t appreciated at the time was that I was going to be working with and overseeing a number of very theoretically qualified desk engineers brought in as part of a technology exchange program with our title sponsor.
That was when a never ending battle ensued, me trying desperately to leapfrog development using what for me was old and hard-won practical knowledge, they apparently more interested in re-inventing the wheel to justify their wages to their bosses.
After 5 years of it I was cured. I went down to Portsmouth, took marine eng exams and buzzed off to play with superyachts. I didn’t have the hassle, the politics, the stress, or the frustration of trying to push the runny stuff uphill with my nose any more. Fantastic!
I suppose that I shouldn’t have taken some of the life decisions that I did, perhaps if I’d stayed in the industry………?
Thing was, I only did it for the truths, the knowledge, never for the bottom line so BS wasn’t part of my act. That is a sure fire way to cheese off the grifters and in a closed environment with one of me and twenty of them I was always going to get stiffed. I know I should have passed on that opportunity and stayed on my own.
Thing was that I hated the limelight, being known. I loved living 24/7 on my own, on the dyno, gathering knowledge, educating my customers and scoring wins off the big players, that’s what made it fun.
Anyhow, on the cam front, I’m firmly in your corner vis-a-vis event timing etc.
I’ve never developed a SBC but have followed the same logic paths with plenty of cams in other lumps.
As I used to say to people regularly, the dyno is the one and only arbiter of what plays better and what doesn’t, repeatable area under the curve is your aim and testing consistency through tight control of conditions and correction factor application is the holy grail. Disbelieve the data generated just because it doesn’t match your world view, you lose and you will never learn to do anything but talk a good race.
You’d not know me if we bumped into each other. As I said, I wasn’t a “face” because I really hated being out there but just so you know, what you were achieving back in the day inspired me to get stuck in and learn to love the hunt for the truths.
Thank you Mr Vizard, you gave me the benchmarks of integrity in the job that led to my modest success in motorsports and a lot of happy punters who became friends along the way.
Cheers! Stay safe and well, Rob.
"they apparently more interested in re-inventing the wheel to justify their wages to their bosses"
Preach it brother! Used to be a Ford "Master Tech" and that there is why I'll never work at another dealer. Well, that and the pay.
I agree ! A guy insisted a 5000 Stahl converter is way to much for my 426 Max Wedge drag car Same with cams . He said it's not a small block Ford that revs to the moon . O m g ! 😂
Dyno or not 50 plus years of building some of the best engine combinations ever and countless wins. Sir thank you for letting me absorb your wealth of great knowledge
"I don't have an opinion, I have a dyno." 😎
Awesome
I believe you sir
Do you think Comp Cams doesn't have a dyno and far better data acquisition equipment than Crane ever had? Why do you think with all the R&D that Comp has done that they don't follow David's advice?
@@jonathanschmidt6507 thats why I use Lunati and have them grind every cam I buy. I dont use off the shelf cams as the profiles are just a ball park figure never an exact one.
@@MasterWitchDoctor
What tools do you use to spec cams?
Hopefully not the 128 gimmick.
There are much better ways that actually considers the physics of the engine.
The 128 formula is does not.
Any method for specing a cam that does not consider the design of the intake and exhaust system is just a rough rule of thumb.
"I don't have an opinion, I have a dyno"... well said. I love your books and love this channel. Thanks for sharing your knowledge with us.
I also have many of his books, and they are my go-to when I need help
Comp Cams has a dyno and far more testing experience and better equipment.
Why do you think they don't follow DVs 128 formula?
Guys, sorry for the delays in vidio uploads. Among many problems to do with covid 19 and some legal youtube requirements for me to take over sole responsibility for this channel now Marvin has passed are holding things up. While all this is being resolved I have managed to put some videos in the can ready for a big splash on my return.
Message for Jon Schmidt - the comments you posted have put you even deeper in the hole so if you mistakenly thought you were off the hook - think again!
For anyone that is interested in modern cam tech, I recommend this video and ignore "glory-days" tales from the 70's
th-cam.com/video/wKgKP6nVSBc/w-d-xo.html
How much power does an engine make that breaks valvetrain parts ?
David, what cam design experience do you actually have?
You mentioned that you went to Harvey Cranes class twice, he passed in 2013 and his software was already more than a decade behind the times. You mention that his designs were smooth; apparently you don't understand the difference between a cam that is smooth and one that that is engineered to manage the dynamics (they are not the same thing). Harvey's software never had capability to analyze for that. It was just a primitive DOS based app that could piece together polynomials.
Just to help you and your readers understand, modern cam design uses completely different methods because the work to get a decent design from polynomials is too tedious and time consuming to be practical. That is why cams designed with polynomials tend to have undesirable pulses in them. Any procedure that inefficient cannot be practically used in a process of optimization. Simulation and optimization are key to modern engineering.
@@jonathanschmidt6507 all of it.
@@troymecey
What do you mean "all of it"
All of what?
Not too long ago I saw a episode of Engine Masters on the TV that demonstrated this on a Dyno. They strapped an engine on the dyno that was built. They swapped in three identical cams as far as lift, duration with different lobe separation angles as described by Mr. Vizard. Interestingly enough the conclusion was inline with what Mr Vizard mentions. The engine in this case made more overall power with the tighter lobe separation angle than with the wider angles. I'd like to have seen the engine tested further tested with more cams with tighter angle all else remaining the same, to see if it would further optimize the power output or show the point of diminishing returns, but as always, time is a constraint when producing television shows. Mr. Vizard through years of experience has developed a formula that will shortcut the trial an error process to choosing the most optimized camshaft to an engine build. I can definitely appreciate the knowledge and the experience that is being put out and shared by Mr. Vizard.
This channel is dead for now, find his other channel here: www.youtube.com/@DavidVizard
I Have enjoyed learning more about Engines from you. You are so correct on your results being proven on the Dyno. I have a friend that has since retired from Roush in Livonia. He worked in the Engine building Department for most of his career. Roush has 41 dyno cells and they test and build a lot of different products. I learned from them on their crate engine program sourcing the correct parts to make good reliable power that is backed by a warranty. So again to confirm that you know what you are doing as your testing confirms what you say. Keep up the great work.
David, thank you for sharing your knowledge with us. we are grateful.
This is why I have followed your work and applied the same philosophy in my own work shop and Dyno figures for forty years. Thanks David from down under.
I have watched numerous teachings you have out there. I even had your how to hotrod small block chevy's and big block chevy's books. I didn't know who wrote them at the time, but I know now.
You have inspired me to build several engines. Mostly chevies but a couple of Fords utilizing what I learned from your books and experience.
You always put out the correct information as far as I can tell.
I'm sorry that we are not living closer together.
Although now I am dealing with heart failure and a heart pump and can no longer build engines.
My son is building a 489 with my input and watching you series. It will be awhile because he is building it as he gets the money. We are hoping for around 550 hp and about the same on torque at 6000. We are using stock 781 heads and 2.19 intake valve. A howards cam .600 .600 lift 230 240 dur and 110 centerline.
We will let you know how it works when we get it together.
Again I wished we lived closer to you. We could both learn so much from you.
I'm interested in hearing your results, how much work on those heads?
@@totensiebush just knocked down the casting bumps. All speculation at this point.
David , TH-cam is a great forum to share knowledge, which you do .. but unfortunately it also allows keyboard warriors to try and knock people down .. you teach , published books and built lots and lots of motors and then done unknown amounts of Dyno testing … You are a legend mate ..👍
Do you think Comp Cams doesn't have a dyno and far better data acquisition equipment than Crane ever had? Why do you think with all the R&D that Comp has done that they don't follow David's advice?
Because comp cams is a large company like u said . You don’t think they don’t give r+d parameters to work within ?? Cam on the shelf company has nothing on a guy like this !! That’s facts
@@Poolguy8879 very well said 👏
Great video Mr. Vizard, Watching your videos for a while now, brings back so many memories from the 80’s, we learned a lot back then, I just finished another build myself for personal use and ready to try this thing out, got to love the smallblocks
I read some of the conflaguration on speed-talk. It is a little strange the way good gear-heads will argue with engineers. I remember when a big delivery truck ran into a ditch next to our property. They attached a chain to the frame and my dad came out, looking a lot like you, and told them you are going to put at least two times as much load on the frame as it can take. They said go away pops we know what we are doing. My dad was a caltech-trained rocket scientist. Guess who turned out to be right? Thanks for what you do for us non-engineers. You explain things in ways that benefit us. You have helped me immensely.
I've watched a couple of these now, and very much appreciate truth and facts. A lot of "experts" who play with motors were lousy students--poor in math, physics and even the kings English. I suspect their IQ is sub standard as well. David is a refreshing contrast to that, and not just for theoretical chat, but for real world applications. It has been fascinating to see how my stock 327/365 Corvette heads could be worked to outflow the best aftermarket heads by a real pro. Years ago I gave a set of boss 302 heads to a local guy to port, but he probably reduced the numerical CR and port velocity causing more harm than good. It was not an impressive motor. My main takeaway so far is be extremely wary without measurable proof. Beyond that, David, thank you. Stay healthy, and please pay that incredible knowledge forward.
I built my 4 valve Mazda B6 engine to DV's specs including the LCA using DV's formula. People couldn't believe how wide an angle I used. Everyone said "that can't be right", but it pulls from idle to 8300rpm and I won 3 state supersprint championships with it. It was never beaten. And my final configuration as good as mirrors the power phase of Toyota's 2ZZ's LCA, duration and CR. Toyota agrees with DV it seems.
We trust you David! No BS lol Lets get to this part 2!!
We accidentally stumbled on the 108 centerline trying to make a vacuum rule on a late model dirt car. adv dur.274 int .278 exh lift .505 int and .510 exh. The cam did NOT pull vacuum but instead woke the fireball heads GM Angle plug ported by Crane Cams on a 11.5:1 355ci chevy small block. engine never dynoed but the torque and power was unbelievable.
I can’t wait for David to drop some 4 Valve head and Cam timing Knowledge on us !!!
Me too!
Apparently John has never heard the saying "Timing Is Everything" or has not realized what it really means.
Great content Mr. Vizard.
Timing is everything, because... pulse flow - DV refers to "recovery" a fair bit, I notice. Must be important. On a centrifugal pump, there's a nice stable spot regarding volume and speed, which charts well. An engine viewed as a positive displacement pump is nowhere near as convenient: can't have intake and exhaust constantly open like that.
Do you think Comp Cams doesn't have a dyno and far better data acquisition equipment than Crane ever had? Why do you think with all the R&D that Comp has done that they don't follow David's advice?
I keep coming back to this video, hoping the next video is ready soon.
Thank you David, i am glad to be on the winning team. 🙂
When I first got into NHRA Superstock racing with my low compression 350 check , i had cams from at least 4 manufacturers who claimed that there cam was the one I needed, I wasn't getting ahead!! after reading David's books I have all of them, and Grumpys book I decided to figure this out in my own, with the help of Dynomation, I had cams ground on my specs, and yes I was questioned a few times 20 cams later the car was running 2 tenths quicker with 20 HP more i won't give The torque number's but had a lot better average, don't be scared to try your self , that's how you learn
Looking forward to the next video(s)! I hope this finds you doing well, David.
Thank you for sharing your engineering acumen, looking forward to your continued sharing. Question, how does the formula change with multi-valve heads (such as 4 valve with 2 intake and 2 exhaust valves)?
Mr. Vizard....is simply !!!!AWESOME!!!!
Best regards,
Ben
David thanks for broaching another subject I've had some experience with myself.......I call it Bench Racing BS.......Also loved your video a while back on the AFR Renegade sbf heads. Most of us know these heads are excellent, but the exhaustive analysis you did showed exactly WHY they are so good......Thanks much......Please keep up the great work, I can't wait for more!
I'd like to see a video on camshaft design and valve timings. I enjoy listening to the information you give and know that would be a killer video. Imagine taking up an argument with a professional.
In the 2011 engine masters contest there was a competitor that placed 2nd with a 369 cu in LS engine, that was converted to a flat tappet camshaft. Steve Dulcich wrote a story about this LS engine in the Engine Masters Magazine, called, unconventional power. The entire purpose of the build was to demonstrate the power that a flat tappet cam could make. So yes David the flat tappet camshaft when done properly can out perform a roller cam. Thanks for the great info.
for limited rpm applications sure. but fact is a hydraulic roller wouldve probably made more power if specced the same.the reduction in friction alone isnt something to be ignored.
@@b.c4066That is where you are so incorrect, if you study how a flat tappet cam and lifter really work you will find where a roller cam has 18 needle bearings and the load is on maybe 4. Where a flat tappet cam the lifter is hydroplaning over 1000s of balls of oil, the same way the engine bearings, and the lifter is spinning. And w ceramic lifters toe friction is next to nothing.
Do you know that Porsche took one of their engines and replaced all the bearings with rollers and needles and it LOST power, so much for friction.
@@racerd9669 lol. Everyone thinks that they need a roller cam to make power. You can't tell the younger generation anything ( YOU KNOW THE ONES THAT GOOGLE EVERYTHING) There is no common sense nowadays or should I say there is a huge lack thereof. 🤔 OH my what do we do about it ? 🤷♂️
Flat tappet cams because of the lifter diameter and contact location can accelerate the valve off of the seat quicker and increase the area under the curve... = More torque
The flat tappet can be ground different! Don’t get me wrong I love a roller but it has it’s place
love it cant wait for more of your Expert knowledge on engine building proving you point with Dyno proven horsepower and torque numbers
I absolutely love the way you call out the BS! Experience and facts wins every time.
Do you think Comp Cams doesn't have a dyno and far better data acquisition equipment than Crane ever had? Why do you think with all the R&D that Comp has done that they don't follow David's advice?
I want a purely, non BS camshaft!!!!😆
What would be the lsa formula for a sbf with the same valve size? Or is that universal.
DV I"ve learned more in a year watching your videos then the last 20 years of drag racing
Seems to me, what the engine builder is trying to achieve is an optimum air flow velocity through the intake port for each crankshaft angle along the intake stroke. Piston velocities and accelerations are the curve balls here.
There is much more to it than that.
An engine is a system with sub-systems. The valvetrain is one of the sub systems.
If you don't design a valvetrain as a system then you end up with a system that either puts too much stress on the parts because the valve springs are stiffer than they need to be or you get other dynamic problems like valve bounce and or broken parts.
Just because you might not be thinking about cam motion dynamics, that doesn't mean that your cam designer isn't. You are relying on them to do it for you.
Let's consider how that works in practice. Let's say that you are a cam designer, designing cams that will be sold in catalogs, you have no idea what parts will be in the engine. So what do you do? You design for and engine with heavy steel valves, springy pushrods, and rocker arms because that is the safe bet. If you design for light stiff parts and the engine doesn't have them, it will likely float and bounce valves and consequently break parts.
If someone with an engine with light valves, good conical springs, stiff pushrods and rockers were to use the cam designed for heavy flexible parts, he would be leaving a lot of performance on the table. Those lighter and stiffer parts can handle a much more aggressive cam.
So when you choose a cam, you should know if the cam is designed to match the mass and stiffness of your parts before considering anything else.
You remind me of a mentor when I was starting out in the 70s, you may know him. He was a British man that love to race jags and mgs. Very smart man made me think and prove to him about everything.
hey would making the 461 double bump head 1.94 intake and a 1.60 exhaust be beneficial
Hey David I have a question for you I want to get the most power out of my SBC but it needs to pull stock vacuum because that's the rules of the class I race in what would your recommend?
I was thinking 450 intake lift 460 exhaust lift 224 @50 duration on both intake and exhaust and 114 LSA or maybe 112lsa and degree the cam ahead 4 degrees would that work?
Pls sir will you help with the best cam for my 333 windsor build must be a roller for a twin turbo valve are 2.02/1.6 heads edelbrock rpm. You learn me a lots thank you sir
David, Got a question, should I loosen the LSA on 4x4 vehicle, like one or two degrees, for just a bit more low end, or just shorten the duration?
Saw some old Mini racing. That stuff was insane! Very cool competition!
Good evening let me start by saying I watch all your videos and I really think you know your stuff I have a 427 bored 0.60 over it has a 30cc dome pistons with AFR 265 fully cnc ported heads a Howard's hydraulic roller with solid roller lifters it is 235x241 duration @50 618 lift on a 108 lsa it has a Victor Jr intake with a Holly 850 do you think when it goes on the dyno it will make 500 to 520 hp? That's what I was shooting for. Any feed back would be appreciated thank you your friend from Louisiana Rick 427
Years ago I ran and used to build some pretty good, for the time, ford cleveland's. All small port (2V) motors, because they were the readily available head here in Australia. I just sat down and did some maths on cam selection out of your How to Build Horsepower book. By pure chance, my best motors were all within 1°or so of your guidance. Pure luck on my part, pure science on yours. I wish that I had read more of your books when I was younger. BTW, a lot of the guy's that I raced against had the large port 4V heads and even the SVO alloy heads.
Since the Cleveland heads have canted valves, you should use 131 instead of 128 on the formula.
You can go a little wider since the canted heads work better.
@@earlbrown if you read DV's book he uses a formula based on valve size and cid per cylinder. It then has adjustments for compression ratio and valve angles
@@theshed8802 I have read his books. That's why I was able to tell you that canted valve Clevelands use 131 instead of 128.
I had no need to mention compression ratio adjustments because you didn't post incorrect information about that.
those of us who seek knowledge of engine science cant thank you enough mr vizard very impressive work sir
Check out new channel, as David can't receive messages comments from this channel after Marvin's passing.
David, tell me what I need to get the L sep correct. 355, 2.08 int valve , I get 104.55. I presume that would be for 10.5:1. I have 12.5:1. So is it 2 deg for every point above that? Am I correct on these calculations? The cam I have is a roller with 106 ls but it seems to run the same time on the 1/8th if I shift it 6900 or 5700. Could it be the torque is awesome compared to the HP? I've never had it dynoed . Not trying to pin anything on you just bewildered on this combo.
David, in your equation how does boost affect / change the optimum lobe seperation angle.
What do you think of the 3VCHI heads ?
+5 hp by changing muffler bearings.
What do you think about changing secondary timing chains with gears on a coyote? My chain broke
what formula do you use on a 4 cylinder to fuger the lsa with a 2 valve
I like watching because, I often learn something. Often, it goes over my head, just like in high school.
But this time, I was having flashbacks of standing in the principle's office, listening to the explanation, as to to why i'm about to get 6 of the best.
Will this formula work with forced induction, will you need a different LCA? Will this formula work with engines in the low 300 cu.in. range?
Howdo David,
I have built a 305 cubic inch small block Chevrolet, 10:8/1 compression, standard small valve heads that are ported and port matched, the research I did at the time recommended a rv type cam ground at 108 degrees lobe center and advanced 4°, try as I did, I couldn't find a catalogue cam to suit these specifications, so I enquired the local enjine builders and they all argued and ultimately refused to grind the cam I requested, so I have so far retained the standard Camaro cam advanced 4°
The enjine has 11/2" headers, 4-2-1 @32 1/2" ,a weiand stealth intake manifold with a 450 Holley spread bore carburetor. Electronic distributor and good quality ignition leads with champion spark plugs.
The enjine was originally designed for running propane gas as fuel, at 106 octane
My estimated hp.rating was 300 and 250ft/lbs torque
Do you consider I'm somewhere close to the mark for building this small bore Chevrolet?
Many thanks for your consideration
Ed
Hi Dave. Can clarify on the 128 formula does it computer LCA or LSA? Thanks
David, do you have any material on twin overhead cam 4 valve engines I can buy?
i respect the raw nature of your words in this and all of your videos. mad respect to you Mr. Vizard
David , what is that Ford part numbered Sig Erson cam you spoke of? Cheers
@david vizard performance do you still have a cam program? I am building a 2.3 lima ford motor for dirt track this off season and need to pick the right cam.
You're awesome David Vizard. I was curious, from what I've heard cam timing changes the centerline. Can cam timing correct a bad centerline or does the correct one (like your formula produces) need to be ground in the cam period.
DV chart is lobe separation angle.(ground in) Installed centerline is determined by dyno testing on each individual engine.... Due to combination variations only testing finds the exact position. DV explains this on another video.
Hey Dave, you need an 'answer to Mr Dyno' t-shirt.
Great video mate.
Definitely getting a 108 for my next 355"/2.02valve Holden.
Where do I go to buy your book or get your program?
Keeping it real as ever, thank you so much.
Great videos, what's your thoughts on power adder's, is 1000hp possible on a budget street engine?
This channel is dead for now, find his other channel here: www.youtube.com/@DavidVizard
On your 128 formula do you have modifications to it if let's say your running a 9.5 to 1 compression ratio or other compression ratio?
9.5 -1 is well within the applicable range for DV's 128 formula. But yes, in his books he details the small adjustments needed for varying compression ratios. Still, the 128 will play very well with 9.5-1.
Is it realistic too compare solid lifter setups too hydraulic lifter setups tho.
Hydraulic lifters always loose power via oil squish in the lifter.
Out of contexts, but can I bore a 5.7 hemi to a 383 and keep the stroke? And what cam would you start with. Been watching your videos for a while now. Thought you'd be the one to ask.
Bruce B
I have watched a lot of your videos I always enjoy because you teach me things I didn't know not everyone can do that you're a very smart very good engine builder but you don't need me to tell you that just keep doing what you do there will always be nasayers no matter what.
A friend built an engine for hot street and he used a chevy performance 'off road' cam (kinda like a circle track grind) and used 1.94 / 1.5 valves instead of the usual 2.02 / 1.6s .. He said because of the lighter valve train he could zing it up and it loved sitting on 7000 all day if it wanted to.. I reckon 1.9 with 1.7 exhausts could be a good combo for a turbo / supercharged engine because you want to clear the old mixture out of the cylinder as much as putting as much new mixture into the cylinder as possible!
The only explanation I can think of for the proliferation of 112 LSA cams, at least for stuff like LS engines, has to do with the operation of the EFI and the bias in the head design towards emissions, smooth and quiet operation. You're absolutely right, the tighter LSA is going to work way better if the wants it. No question at all, there is going to be more power and TQ everywhere.
That is correct for dyno testing,,,,but; most people will regret the narrow LSA after they deal with the poor drivability, eye burning exhaust (pollution negligence), it gets old after a while.
Anyone that tells you that the cam companies don't know what they are talking about is taking you for a fool.
Of course all of them know they can make more power on the dyno, but there is much more to choosing the best cam than a dyno test.
OEMs do double blind testing to see what customers actually prefer, the fact is, the drivability they choose is not the same as the dyno chart they choose.
When I was working on the Coyote intake manifolds, customers that did not know what manifold was on the car thought that the truck manifold was the most powerful because it had a lot of power down low.
Thanks a lot David ,I do agree , however just to take note for future video it will have been nice to have the dyno graph to compare ,I do understand that it is not always easy to have exact comparison specially going back to data which have been recorded long ago.But if you can incorporate those graph next time it will be appreciated.
Best regards
ps :when do you think you will be able to have an episode on 4valves per cylinders head porting.amd how will you use your program on those type off head.
My hubby builds hot rod engines and totally enjoys your videos !
How much do you charge an individual for a cam recommendation, based on my engine specs and intended usage? Do you do those for non-Chevies?
I believe you sir. I think you are a true "guru " of tuning and combustion technology. Have you ever tried to explain how volumetric efficiency is so varied in engine design?
Thank you for sharing Mr. Vizard 🍻
The Camshaft is a critical part of an engine build. I love the 4.3 Vortec V6 engine and I put a Comp Cams 266HR in my 98’ 4.3. Beehive springs, chromoly pushrods, mahnum roller rockers, mild porting. I feel like I have less torque than my 94’ 4.3 CPI motor had. I believe the added spring pressure takes away power. The extra energy it takes to turn the camshaft has to be the culprit.
it is probably the mild porting to blame. it needs precision expert work around the seats and valves, chamber and bowls.
I would disagree, that the camshaft takes more energy to turn. Most people forget that a camshaft has an opening ramp and an closing ramp. While it might take more energy to open the valve than the stock valve springs as the lifter goes up the opening ramp, the stiffer valve spring will also add more energy than the stock springs back into the system as the lifter goes down the closing ramp and help turn the camshaft. So net energy is zero or close to zero.
My '94 Blazer would smoke my '99 Blazer both in power and gas mileage. When I lost my radiator hose and blew up the engine I made the best of both worlds.
Fast burn factory Vortec heads, unshrouded the valves and put 1.6 exhausts in (basically sbc chamber mods), a CPI cam, removed the balance shaft, and decked the block .015" to get my compression back and move the quench from .060" to .040".
It's the engine GM should have build when they got rid of the CPI engine.
Terry Walters has made some big power numbers using the Vizard COS cam selection program! Hoping to see some dyno time on mine soon!
Thank you for sharing your knowledge. Looking forward to the next video.
Do you have a similar formula for a small block dodge magnum?
The 128 formula will work great for a Dodge Magnum engine. If optimized power for your combo is your #1 goal. Your going to sacrifice idle quality and manifold vacuum, but you will make the best mid to upper midrange power possible.
May I present a question for you?
Have you ever competed/assisted with a top horsepower shoot out like engine masters? Thanks
On your video on centerline angle for factory iron heads you say absolutely 108° CL did I hear you say with 1.6 rockers go up a number to 109°? I checked my Howards cam is 106° with 108° lsa with modded 993 heads is 106° CL holding back much power? Which is more detrimental to power lower or higher number CL? Because even tho I love my cam it runs great sounds awesome but I trust your opinion and would consider cam swapping if it's worth enough like 20hp but likely wouldn't for like 5 or 10hp because of the expense of a new cam I'd rather put it in a different mod you suggest. I'm completely rebuilding/further modifying my 355 with your tech tips I'm excited to see improvements from your tips and tech so thank you DV you are my inspiration and I put your advice and rules over absolutely anyone's and when I watch guys like Steve Morris even tho he's very knowledgeable I think I wonder what DV could do to his BBC and SMX heads, I bet you could find improvements in even SMX heads especially the BBC stuff like the Big Brodies.
David how can I contact you for a cam profile on my drag engine. A 368 SBC with a 2.100 intake valve diameter?
I have issues with any builder or gear head when they say I got stage blah blah blah...I tell them that means nothing. If you change engine dimensions you need David vizard cam calculations for optimum power!! His cam advice is true in my case. I built a healthy 351w on techniques I learned from David's how to build horse power books. My math ended up with a 108 lca cam, I bought a cam not custom but generally close to the lift and duration needed also due to advice from dvs books. The engine ran phenomenal
I remember that s*** show of a thread on speed talk
I was signed into that forum when it was all going down, and really didn't understand why people had such a beef with your formula
The whole premise that you put forth was that this was a tool that the average hobbyist could use to get a pretty good result on an SBC, (and would even be in the ballpark something similar like MoPar wedges, Windsor Ford's, etc)
The funny thing is that, even as a casual hobbyist, The trend that your formula shows wasn't a complete surprise.
It's been pretty common knowledge that when you build a stroked version of a given engine, they tend to like a little tighter LSA, and that highly developed engines with excellent cylinder heads and large valves (Comp Eliminator, Pro Stock, etc) can end up running fairly wide LSA cams
Applying this formula to my 489" Plymouth with 2.14" valves (if it is truly a good application for this formula) calls out for a cam ground on 102°
Should I run out and have a cam ground on a big $$$ custom core to get that LSA? Beats me.
But I suspect if I want to buy another cam, I should be looking to see what I can get on a fairly tight lobe center
If nothing else, it would save me from going out and buying something ground on 112°...
Doing any active dyno testing soon? Thanks
Correct me if I'm wrong but I'm trying to learn. It's the over lap plus the centerline that equates the advertised duration? If so which part is the most important. Say you can get a cam with the correct centerline or with the correct amount of overlap which is the smarter choice?
No advertised duration is a separate dimension for each lobe (ex and intake). Has nothing to do with overlap.
another great video, thanks for sharing your knowledge. Question- I think I heard on a TV show that EFI engines require wider LSA vs. carbureted engines. So, in the 350 10.5-1 with 2.02 1.60 valve example that you give, would 108 LSA work best on carb engine, while an EFI version requires wider? or is that wrong?
They originally did that to tame the idle because a rough idle drove older FI systems nuts. The engine doesn't know how it got the fuel it just burns what it got
@@jimdouglasgregory thank you
I love the detail an facts you provide, I am still hoping to see your video on porting PARKER FUNNEL WEBB intake, any chance is that coming soon?
I love confidence David. You have it 👍
Thanks DV, I would not dare question your authority on the 128 cam formula as your results speak volumes! My question is what modifications to this formula (if any) would I need to apply to a 4 cylinder 16 valve application as this is my main interest and I live where I have limited options to chose from in profiles locally? Any guidance im this would be much appreciated. Thanks for your pearls of knowledge, always valued👍
Do you think Comp Cams doesn't have a dyno and far better data acquisition equipment than Crane ever had? Why do you think with all the R&D that Comp has done that they don't follow David's advice?
@@jonathanschmidt6507 You should post some videos to show why DV is wrong instead of copying and pasting this same comment over and over
@@stevej4135
I have explained it many times in discussions on speed-talk.
DV called me and invited me here to help stir controversy so that he can get more views.
Can exhaust scavenging create enough vacuum force on the piston to present bearing problems? I had a Pontiac 455 that ran 3800 rpm at 80 mph and pulled 22 in hg. Full length 2.5 inch exhaust. 4-2-1 collectors and x-pipe.
I would say no. Bearing problems are almost always a lubrication problem. In extreme cases you can get into alignment or deflection issues but most automotive bearings have the size to handle any loads you can put on them before the block gives up if the lube is good.
Overlap
Does the 108 hold true for 18 deg or sb2 type heads or is is it 23 deg only?
The 18 degree heads work with the 128 number.
Love as all do… “I don’t have an opinion, I have a dyno”
But even better the end part
Showcasing one of Jacque Vizard’s masterpiece thank you!
Hi David, on some Superflow dyno tests they show bsfc values for performance tuned engines that are below 0.4 #/ hp-hr. Could that be accurate?
yes
David: I've found that the quality for Edelbrock products are lacking in form and craftsmanship. Competition Cams Co. is kind of the, "run of the mill' products...sometimes with Edelbrock as well. What are your thoughts on these products. I very interested in finding the correct parts for my builds in application.
Hay sir.have a 327 small jurnel.flat tops.and.906 vortec heads.what the best cam for it.street and strip.thanks tom
This channel is dead for now, find his other channel called David Vizard.
@SinsBird good to see other's trying to help. 👍
Mr Vizard, I've been reading your works for a very long time and was tickled to find you posting here on TH-cam. Thanks for all that you have shared. That said, I think that maybe this video was a step too far. The internet is full of blustering warriors, the vast majority of which know less than nothing. I confess in years past I myself have been drawn into arguments online that I probably should have just ignored, but we're all human. While I would wager you are most likely correct on this particular topic (and I don't even know who the other individual is), I frankly couldn't glean enough from the video about who was arguing what to be sure. It sounded like this individual insulted you to the point of raising your ire, and you felt the need to respond in a way that, I feel, was beneath someone of your stature. Keep laying the facts on us, and I'll keep watching. Thank you again for all you have contributed to the automotive community.
Mr, Church Automotive, This guy is a little off the norm. I suspect he has a pretty high IQ but less than what we may expect from such for logical reasoning. The reason I jumped on his case was because of the BS he was spreading.
Very well done presentation
I can't remember where I saw it but in a video somewhere I saw a Dyno room Door with a small license plate over the door that simply read "Lie Detector". Seemed most fitting.
David, What are your thoughts on roller bearing camshaft tunnels. Is it a case of lots of $$$$ spent for little gain ?
I don't have experiance with a back to back here but a vey siccessful Nascar fried of mine said it was wotrh power but only a little.
My problem is with these aftermarket companies and everyone of them claim that they are the best , how are we supposed to know who really does make the superior product ? I find this maddening that everyone can claim to be the best without a shred of proof !
Is there a version of the 128 formula for other engines? For example, I'm a big fan of GM V6 engines, and would love to have some math to help with camshaft selection.
The formula works for all engines.
The formula is tied to GM style heads of that type / era (SBC)......David is likely 100% correct, BUT as an example the LS, canted valve engines, and new gen hemi's all have better overlap flow (by that I mean more flow), therefore there LSA's would be different / wider for those types of engines.....I would venture to guess that David's formula applies pretty well to your GM-V6 (especially if it's a 4.3L because that's a lopped off SBC at heart w/Vortec heads, if its a newer one.
@@ericschumacher5189 - Thank you for the intelligent response.
I agree 100% and you have the proof. You would think it would be common sense for an engine builder.