Hyper advanced ProStock-plus, cam tech.
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- čas přidán 25. 08. 2024
- In this, episode 85 of PowerTec 10, DV delivers the ultimate, most informative, cutting edge presentation on cam/valve event timing. Here is a guaranteed, set in concrete claim, that you will not be able to get this kind of tech anywhere else, even from top ProStock engineers.
Going into this you had better be prepared to pay close attention and too fully absorb all of what will almost certainly be unfamiliar tech. As a result you may have to watch two or three times. However, if you are a professional performance engine builder this video will save you money on cam selection and put you at least one step ahead of your competition.
David, I have used your teachings to "spec" out camshafts in 4 different cars in the last 6 months for friends and family based on your teachings. 3 out of the 4 are 11.0:1 static compression "street" engines that run on pump fuel, 4 different engines 383 SBC, 351W, 351C, 460 BBF the Windsor is a turbo setup and won't be completed for a little while however, the cranking compression on all three of the others is over 205 psi! and they run extremely well. The BBF had 185psi cranking compression before we made a cam swap following your teachings and now its 215 with NO other engine changes and the camshaft duration is within 2 degrees of the old camshaft just on the correct ICL!! needless to say, it's a bit faster than it was last year.... What is funny when people ask about how we learned this most people think we are crazy. LOL The 351C has 210psi that engine we actually had a camshaft that was too big as a 351CI (180psi cranking comp) but was correct at 406CI so we stroked it to match the cam setup and needless to say it runs really well now... I say all of that to say this for the better part of 20+ years I couldn't figure out why a 350 SBC that I had when I was a kid did not run very well for the amount of money that I had spent then I bought this book that changed everything... David thank you for sharing the information to a bunch of frustrated people like myself it makes it much more enjoyable pressing the go petal now and seeing the results go up in tire smoke :)
Tell me more about your Clevland, please?
Thank you David!
How can the duration of the camshaft be estimated once the LCA has been calculated? Thank you
Where did you find how David specs cams ??
This is very interesting @jeremysorrell3762 do you know the dynamic compression and intake value close timing of the 383 with 11:1? By pump gas I assume it is 93 octane?
Thank you David. I have been a disciple of yours since 1980. I started with " How to rebuild your small block chevy " and progressed through "How to hot-rod..." I'm retired now from the aerospace industry, apprenticed at the Westland helicopter group in Somerset, England, and educated later through the Garrett corporation and Nasmyth. In the manufacturing of super high speed turbine shafts and such, when using a very sensative comparator to measure shaft diameters, it is possible to witness the changes in diameter of the component simply by handling the shaft with bare hands as you measure. Normally you don't do this.. you glove up.. and isolate the shaft in the standards room to regulate the temperature before final inspection. But I have always wondered how much accumulated deviation can occur through the entire valve train through temperature changes. Of course.. we are talking about massive differences from the effect I witnessed from just handling the component at body temperature... I would be very interested in your thoughts and experience concerning this with regard to engine temperature. Actually, I am fascinated to learn of possible effects because many materials are used in valve train.. and all are likely to display different expansion ratios from one material to another. Thanks for everything over the last 44 years. I have learned plenty from you, and my little dabble in ameteur drag racing was massively improved by your advice.
Thnx for the Shout Out! Dave is a legend
Richard - you are more than welcome!
Two of the most knowledgeable engine guys right here. Man you guys should do a an engine build together I can see it know 434 sbc best of everything most hp on 93 octane boosted with 8 71 roots blower with Dave's knowledge of finding power where others don't and Richard's turbo and dyno know how I would pay to see that shoot I would buy the motor
Both of you are legends!!!
DV in the pre pollution days 108 Lsa were used by manufacturers like holden to improve low speed tq and compensate for less than average head flow. Totally agree with your statement. Turbo Ls guys bang on about wider separation however a 108 still produces best results. Rock on David. Wish you well.
I remember back in the day , hot street cams for Holdens and chevs were referred to as 30/70 or 35 /75 (280/290 duration) which were close to the 108 with 60 or70 deg overlap
The thing here seems to be getting order of approach correct. We could say that duration is the derivative of all other choices, and that seems right to me. LSA yields an exhaust pulse derived signal efficiency for the overlap serving the intended intake/head/exhaust combo for a fixed bore size: change bore or valve size [with all other things constant] and the in-filling characteristics for peak efficiency changes. Selecting intended rpm usage to start off with leads to choosing overlap, then best lsa is a fixed value on account of bore [and valve] size. Next, a lift that gets its worth out of head flow but doesn't have ramps so intense you can't control lifters, or find oil to handle insane spring forces that do provide control. Duration? Product of all the above, with the ability to lightly shade some characteristics as evidenced by dual pattern cams. It ought to make sense that fixed geometry values provide fixed results: bore, chamber, valve diameter etc - these things never change once built. Bill Jenkins mused in 1976 that however he built a sbc, he always seemed to come back around to 109 lsa, and no telling how many combos he tried getting there.
I remember doing some shopping with Luigi Rapisarda at Rare Spares in Homebush, this would have been 1984, and two young guys walked in to buy a camshaft for their Holden red motor six.
They salesman layed the range out on the counter and the young kid asked what the biggest cam was.
40/80.
The kid said instantly, "Well, I'll take that one!"
The world was a lot simpler back then.
DV hadn't seen a video in a few weeks from you, was starting to get worries. Thank you for taking the time to put a lot of this together in one video. It is a wealth of information. I have a suggestion for a Part two to this video. Could you go into how to choose the overlap and how to determine the right duration? I think that would bring the whole package together. But then maybe all of that is a trade secret. Thanks for putting in all the work to help us take all the guess work out of building a great engine!
Good shout
thanks i built my 355 chevy cam at 106 others told me i was crazy but i made more power than them so the proof is in the pudding you are a plethera of knowledge
106 is perfect
I used to own a performance shop. Mostly late model gm Ls. I sold it years ago. I just have been amazed by our channel. I have learned quite a bit. I just wish i could have seen your channel 10 years ago.
I already knew most of this, only because I'm one of your greatest students and read every one of your books pertaining to this subject literally hundreds of times. This reinforces everything I've read. Thank you good sir!
Fabulous!
This video confirmed 99% of my suspicions...
I always appreciate the thorough explantions given as to the WHY.
Thank you.
My suspicion has long been that there are some cams out there partly "designed" by a sales department. Trends developed based on 'bigger is better' theories in the general public, and so LSA's got pushed to larger values to stay away from poor idle/vacuum issues and customers complaining [about what really was their poor choices]. Detroit bears some responsibility in that maybe the explanation of muscle era cams lacked a bit. Something near the 300 duration family of that day was very long to get off/back on the seat when compared to 0.050" duration - double a circle track cam of today and change. Those were blended decisions in probably this order: warranty, sales, and performance.
Thanks for the video. You actually know what you're talking about. It's getting harder to find smart people nowadays.
You've spent all the money, you've done all the work, you've studied the information, and you've figured out what that information is telling you. I know whose information I'm using to specify a camshaft for myself and my friends.
I've been using it for years and years since Denny Wychoff was at Motor Machine and Supply in Arizona with your Cam Master program.
This work is outstanding.
Thank you David. I finally understand cams! This video is clearly a "secret" of the successful teams... your experience is priceless!
Big Moose - No the video is not a 'secret' of the successful teams. I bet you could not find a top teams chief engineer who could have told you what you have just watched!
@@DavidVizard Thank you again David! The info and insight is priceless!
Many thanks David for all your information especially when you mentioned about the reason boats get water back up exhaust etc.. Changed cam in my jetboat out here in New Zealand to what your guide lines recommend and wow! What a differents 😲😁👌Thank you so much👍
I got a copy of the Cartech Gen 3 LS1/LS6 book. In the cam section it lists the factory cams used. Duration is the 0.050" spec. The 4.8L and 5.3L are 191°/194° with around 114°/115° LSA. This is with lift about 0.456". When it lists the LS6 cams, duration is up to 206°/218° with 117.5° LSA for the Corvette cam. This with lift of 0.555". A big advantage of the Gen 3/4 engines is port flow and swirl. Exhaust emissions and fuel economy with a docile idle for the majority of consumers is a major concern. Reliability is also high on the list.
Then in the GM Performance Parts they show 2 cams, partly known as ASA cams. For these a smooth idle is not a concern. Duration is in the 236° range with lift about 0.525" and LSA is reduced to 112° and 110°. With longer duration and narrower LSA, the overlap will be up. Idle quality and emissions will likely suffer, but for a race or street rod engine they should function well. Pretty much falls into what DV states.
The OEMs have been in a contest over advertized HP. For street duty it is torque that rules. You want to run Indycar or Cup Car, HP is king. To get the HP numbers the ad guys want, port flow/port energy is required. HP usually requires higher RPM, so bigger ports. To keep the emissions and fuel economy we have seen the OEMs go from 4spd OD, to 6spd, 8spd and lately 10spd automatic transmissions. This is to enable keeping the RPM in a narrow band they engineer for. This is the theory behind CVT transmissions, which are proving to be troublesome. The 10spds also seem to have some issues. And EV's in my mind are a dead horse, at least for now. How zero emission an EV is depends on the carbon footprint of manufacture and the source of electrons to charge them, until the batteries do a Chornobyl event.
A quick and easy to implement answer to reducing emissions would be natural gas. Enough of me venting my spleen.
This is very true. Natural gas is cheap and burns clean.
@@SaddedudeThe problem with natural gas is the energy it contains. It does not contain the energy that diesel.and gasoline fuels contain. They do however possess a high octane rating. What this means is that much more is required to get the same power output. The high octane allows to use high compression ratios. Converting a diesel engine that has a 15:1 to 17:1 CR is fairly simple, and runs well. The clean burn allows the oil to stay cleaner longer.
@daledavies2334 When liquified the energy density goes up quite a bit.
@@SaddedudeThe storage state of the fuel is not the energy density. Energy density is the nimber and arrangement of Carbon and Hydrogen atoms in the fuel molecule. Natural Gas is predominantly methane which is composed of a lot of H2 molecules. Natural gas is a bit lighter than air. Propane (LNG) is heavier than air and has a higher energy density than natural gas. Either could be injected as a liquid into the cylinder, but there is no advantage to speak of. You still require more, which equates to poorer fuel economy on a conventional.gasoline engine. An engine built to run LNG can have a CR of 13:1 or 23.5:1 and will give a similar fuel economy to when it ran on gasoline. Similar is natural gas which has a higher octane than LNG , and can use 15:1 to 17:1 CR to recoup fuel economy.
Energy density is defined as energy per unit volume...that is literally what it is, and that is all that it is. Just like miles per gallon- you divide miles by gallons. For ED, divide energy by volume, in your choice of units.
Calories per bushel is energy density just like joules per cubic meter, or cc.
Methane is CH4...no H2 in there. H2 is a diatomic molecule,...in methane, the "H" bonds to the "C", not to another "H" as it does in gaseous hydrogen, to become H2. Octane is a chain hydrocarbon with, again, hydrogen bonded to the carbons (8 carbons in this case), and the carbons to each other.
The energy released depends on the sums of the energy of the bonds either broken or formed during combustion.
Hydrocarbons are pretty energy dense in general, and relatively easy to handle. Great fuel, outstanding, really. More energy dense than most explosives, by far, and so controllable.
Hello Mr. David Visard. Thanks for the stories and entertainment. As stated before, for many years now I have been putting into practice what you have shared. Sometimes because of clients demands I have strayed from your findings and went with what would make their wishes happen. That being said it was agrivating to me because I knew that performance was not what it could have been. However, when the restraints are off most of my clients are pleased with more than they expected. Also, because of what you have taught, for the most part I have been specifying my own cam specs for years now. I also use Jones Cam Designs when the budget allows. I have bought multiple cams from Mike now. Cheers !
Gday DV, yes I have most of your books. This episode is easily the best, most comprehensive summary of your experience over he past 50 or 60 years. Best ever. Easily.
Thank you Mr Vizard for all your dedication and effort, your gift of knowledge is priceless. Thank you for explaining 128. Keep up the good content!!
Thanks for your generous support Victor. Every little bit helps upgrade our presentation capabilities.
@@DavidVizard David. Your a Genius. Sorry not trying to Hi jack your comment. I just need to know when your offering your next seminars.
David Vizard I can’t thank you enough for the education you’ve provided me simply from just watching your videos. These techniques I’ve learned from you I will pass down to my two sons as they become older and they will be ahead of the game at a early age. I’m 45 and I’m still learning everything I can about tips and tricks to improve the internal combustion engine and these videos you’ve made are the best and most informative I’ve seen yet on the internet. Thanks once again and to you sir, all the best!
You can always donate if can’t thank him enough
The most solid explanation of camshafts I have listened to. Thanks for clearing up the cam sorcerer mumbo jumbo and giving us a usable plan for considering a cam. Thanks for everything you do. Looking forward to the next video.
My comment is to say I enjoy learning about these things . I remember reading a lot of Smokey Yunick’s things he did to get more power ! I love to listen to David an the way he breaks things down then explains why you get more power . The same way I read Smokey did . These older guys that have been at this have such great wisdom about building engines . I thought that simple things wasn’t all that much to think about but Smokey said all those crank bearings and the surface they seat to. Need to be cleaned real good so that the block and rod will pull heat out of the bearing . Just like David said something as simple as the rocker arm ratio will change the cam center line . Wow that’s something right there that very few people would ever think because your just looking at the math to figure how much more lift you will get by going bigger ! You have to love the workaholic ideas because that shows determination to prevail . Bob Gliddon back in the 70’s was determined to run an win with fords 351 Cleveland so much he convinced ford to make a 4v head for the motor ! From listening to David you can tell he’s telling the truth that he lived through . We would not have all of the great information that he’s relaying to us if he hadn’t did the work to back up what he’s saying . You have to respect a man for all he’s done and has laid his hands on to be able to educate you on things you don’t know or may need to know latter on . My hats off to you David I didn’t know a whole lot about you before your channel . But the best kept secrets always come out in time Smokey and Bob did great jobs but they were driver / engine builders . From listing to you I have to say you would know way more than them because you stayed right with the engine . You wasn’t out testing a car for the track and bothered with suspension problems set ups and so forth . I highly enjoy all of what you explain and how we can improve are performance and overall power curve through out the rpm range . Another great video thanks for all you share. I have all the respect in the world for you . It’s great your amount of wisdom and knowledge will help us !
This was one of the best videos I have watched and 100% correct. I don't understand why it is so hard for people to understand.
he's/David's right to a point but memory ( id like to see more on this type of camshaft and multi air system VVL aka liquid-push-rod's+rocker's ) probably got the better of him, as the viper's ( got a 4th-G/2015~ OEM core in my shop to study on for my 2-generation hemi as a pattern, for V-LSA + VVT / twin-phasers out of a chevy/lsx platform ) and or prototype 3-generation ( cutting down ( v8 vs v10 ) and weld+regrind ( 72* vs 90* ) it in theory would be a direct bolting, but i don't own anything newer-vin/car-wise than 1990 and im millennial generation fyi 😉 ) hemi had cam-in-cam with V-LSA and or tiger-shark-platform, might even have worked on/helped it for all i know
still helping me learn for computer setup etc so in general 👍
David, if it had been most other people that sprouted this video I might have said you were full of yourself.
I have been following your advise since the very early seventies and know that you only say the truth and you do not need any more media time or money. The latter is always good to get though. I will probably watch this video many times more so that most of it sinks in. You are a stand out among the educated as you have the ability to teach in a way that is easily understood. Hoping you will be teaching for many years from now. Thank you, Terry from Australia.
DV thanks for the very thorough explanation on cam events. I've watched it 7 times through.
Best video yet, Mr. Vizard. I echo @xlr83VA's request for part 2 on selecting overlap. Of course, once you know the LSA and overlap, the duration falls out. A method of determining a good starting point on the selection of additional duration needed for the exhaust, over the cam duration, and how to estimate the advance to install the cam out would be great too.
Those sorts of concerns would have to factor in flow characteristics of the head. Vortec vs early SBC design as an example. I'm sure the great "Vizard of Engine" has programs written to figure it all out. LOL.
i play with 5v yamahas and 102 degrees is the magic number as is ridiclous comp and unmasking the valves i have followed your work for 30 years and had spectacular results over the years with bike engines , taught me a lot on porting too thanks agaian
Great information DV. Most of your videos I go back and watch 2 or 3 times to get the important tidbits stuck in the gray matter.
Thank you.
What a great pile of information!! I’m going to have to watch this one a couple times to digest it all. Thank you!
Wish I could work with you David, I mean work for you. I'm self taught so you probably wouldn't want to trust me but I've wanted to experiment before with cams, taking away lsa, adding to it. Ideally I'd like to find the perfect cams for x displacement and x flow. With x rpm as a base. Everything you are teaching makes sense, I can see how it works. I hate that other people that have been fooled don't see it or question it.
Seems to be the closer to idle/stalling the less overlap you want. Makes sense when thinking that 0 overlap would give you the most power at idle but you'd obviously have issues at higher rpms. If you read this David, I hope it makes you happy to know you are reaching to young audiences and your knowledge won't be forgotten. I will pass down what I've learned to my children from the Great Wizard of engines, David Vizard.
Benny, Where are you situated?
I realize You are one of the greatest engine builders of all time ! I love your program ! May God bless You abundantly !
I have a pair of marine 318 Chrysler engines which I wish to upgrade. Your insight on marine camshaft overlap is priceless ! Thank You !
I'd like to point out that in almost any Endeavor of life, forgetting the lessons of your grandfather's is the biggest transgression you can make. At work on and around engine since I was about eight years old, and the best lessons I ever heard was from people who rubbed elbows or from the Chrysler Engineers themselves such as Mancini racing, as I was growing up. Great information always. And the other point that I would like to make is that the devil is in the details, and if you ignore the details, you will have hell to pay.
That logic applies to Jesus also ! Hes our creator , the one who knows all things the source of all truth and wisdom . Transgressing his laws is not wise .
One man dominated engine masters, he's a true genius when it comes to engine's.
Good job! Lots of good information, and I look forward to implementing these concepts in my engine builds.
What a fantastic video. There is so much I want to say, but ultimately, thank you DV. Between this, and your books, I feel confident in my "shadetree" abilities.
Excellent video. I have a 438 wendser going to the dyno in just a few weeks with your LCA calculations. We will see. I believe you are right and thanks for a great analysis and explanation.
how did it turn out?
Thank you for your insights, David. I've always been a proponent of using solid lifter cams with high lift, short duration and close lobe centers for my performance engines and they WORK.
Great Video. When it comes to Camshafts I thought I knew a little about them. Turns out I'm wrong. My knowledge doesn't even begin to scratch the surface. Now if you put out another 5 videos explaining all of this. For dummies like me that would be great. I'm sure I need to watch the video again but I didn't see the calculations needed to adjust for compression ratio. Keep the awesome videos coming. Even if the math melts my brain I will still learn tons and tons of knowledge 😌
David, 2 things you didn't explain enough. 1) How much does LSA change per half a compression point change ? Your example is @ 10.5 : 1 but if you can show changing it to 10:1 and 11:1 I can extrapolate. Also, 2) you didn't go into detail about when does the cam affect LSA by quickly lifting the intake valves. If not mistaken I believe both roller cams and solid cams can have the same influences as a fast off the seat rocker arm. But when does this alter LSA and by how much?
nice to see something technical. sometimes you have to stop and think about it before moving on but it's a good way to move forward with your knowledge.
Thanks David! Great class you just held. Loved the lecture. Now off to do the lab work. I’ll hand my paper in Friday!👍👍😂
LCA is different than LSA. As an example: one could place LCA at 106 and make the LSA as wide as 110. In that case, the LCA sets the degree from which the intake valve event is measured. Then the LSA is 4 degrees wider than the LCA, so therefore the intake valve opening event would occur at 2 degrees before TDC.
Great insight DV
And great video , well explained
"In DV we trust"
Keep up the legendary work
Thank you for being very thorough, and explaining in a way im sure most can comprehend. I just recently ran across your channel. The content is very dence, not a wasted minute of information. Appreciate it.
I can only learn. My opinion can not survive a professional unless I beat them with a better combo that I engineered using ideas such as yours. Thank you.
Thanks you make the point in a very digestable why, I live in uk and have a massive soft spot for the ford pinto engine.
It is great listening to you. when I go and talk to my dad who liked putting shorock's superchargers in Hillman Imps his eye's light up at some of your stories of Avngers racing.
The bit about high compression negating lsa effects mirrors the one time I ever did a cam lsa test where I had a 108 105 and 100 lsa cams on a Cummins diesel and I changed only cams and optimized the intake centerline for each. It was a 1500hp motor and in the end there was less than 15hp difference across the 2500 rpm rev range between the 3 cams. At 1% that is easily within margin of error for that not climate controled dyno cell. The 105 seemed to load in better so that is the one I kept but the test revealed no clear winner.
Awesome video David!! I'm going to watch it again!! Thank you...👍
This is great stuff! I started reading your books when I was a young teenager and loved the information.
Thanks David and Andy, best video yet! Very thorough explanation! 👍🏻 Good stuff!
Yeah but it's not digging ditches old sod I had to subscribe last year you're a British master engine builder smart hope the people around you are sucking in some of your knowledge old lads like you and are a once in a lifetime blessing to be taught from when you speak of the old days and people you knew in Britain I love those stories way back people were taught a job or career and that's all they did nothing else especially at war time and knew their job inside out.
what a delight these videos are..keep on speaking truth..
I build my First engine ever @ 20 years old with your how to build HP SBC book ... that was 15 years ago and that engine is a .030 over 305 with trick flow 175cc heads .. don't have numbers but it runs dang good and gets 20mpg with a quadrajet Th400 3.08 gears in a 72 LWB chevy truck
Thank's for sharing from your wealth of knowledge. So much time invested to gain same. Wow 22,000 cam combinations on top of all the other testing you have no doubt done over the years. Amazing.
Love your videos.
Thanks Again & Cheers
Thank you for sharing your knowlege.
It works! I'm glad when people disagree with it. I rather keep the advantage for me and the customers that I spec cams for.
One thing to note the guy that David shows in video is a popular cam grinder for the LS and LT world. They actually offer a cam for trucks with a 107 LSA. I believe it's probably the most successful cam they sell for LS stuff. Funny thing is, it's their only cam with a tight LSA. All the other cams have to wide of a lobe separation based on DV's formula. Wonder why they still don't see the truth?
Thank you so much David. Much appreciation.
It's mind-boggling. Math, geometry and physics definitely apply to this. Yet an engine is complex enough that any change you make potentially changes the optimal form of everything else, and it is really too complicated to approach theoretically, once a basic engine platform has been selected.
What is left is to marinate in the details, the dynamics, the performance data, until the deeper trends become apparent, as you have. There is no shortcut, and your account of what you see after so long scrutinizing changes and results, is a treasure.
Thank you DV..!!! ive learned alot and will continue to make you my go to..im just beginning a mopar big block 400 stroker and i will use your formulas to pick my camshaft and head, valve and rod choices...
David, I saw a video not too long ago where Mr. BTR was addressing what you said about LSA, lol.
Of course he's still adamant about his point of view.
I'm on board the DV train all the way!
Not any more!
David, I truly love learning new stuff or being corrected for wrong stuff and being given direction to apply what I have learned. You old guys (I know cause I are one) I look to, before God calls you home, to pick as clean as Thanksgiving turkey all that knowledge and experience so I can apply, learn and pass on. The good stuff seems to always get buried or you hiding in some shop working your ass off as you state (workaholic) and when you take time to do stuff like these videos I always push subscribe and comment so you will know how much I and others appreciate all you do.
I was thinking about cam timing when I thought that if you use a free valve equipped engine as a test mule you could do what Chevrolet did with the intake that has three butterflies internal. Just set the engine up on the dyno and tell the computer to do multiple runs until it finds the optimal settings be it peak hp or peak torque or highest average torque or highest average hp. Then just grind those settings into the cams built for a certain engine package. In this case it would be ideal to sell the cam as a package with heads.
You're wrong on one point; Mike Jones isn't always grumpy. Great video again. Health and happiness to all. Cheers!
In my limited dealing with him I've found him to be a no nonsense straight up dude that expects to be compensated for his time and expertise. The only folks that find that grumpy, or rude are people that want to waste his time, or gain the benefits of his knowledge and experience while never having bought anything from him. He takes very good care of his paying customers. Operative words being paying customers. There are only so many hours in the day, many would have him waste his time and not compensate him. How grumpy would you be if your boss expected you to stay over 2-3 hours talking shop after you clocked out? He is no different than any other rational adult that expects to be paid for his time and energy.
Ted, I do know he is not always grumpy - just sometimes. Also I like to call him grumpy just to keep him on his toes. He treats me well and is always ready to help out. Does good cams as well!
@@b.c4066 I think you have basically nailed it here. Whatever others may think he has treated me royally. (thanks Mike)
What happens in the combustion chamber is only a small portion of the entire system. It's one big air pump. Easy in/Easy out. The more restricted the air movement, the more cam timing and overlap is required. The optimal cam events are all determined by the ability to move air.
Newer engines actually need to Alter from older practices because of the less restriction. What worked on earlier engine families doesn't directly transfer to modified or newer engine families. And the practices are also different for multi valve systems.
As you stated....let the engine tell you what it wants.
Possibly the other point you're missing is we design our own lobes in house and test them on our own Spintron and Superflow Powermark engine dyno. Those pieces of equipment run practically every day. We also grind cams in house on our brand new Landis LT1e cam grinder. I welcome you to take a trip to Bardstown KY so you have a better picture of exactly what we do and how we do it.
Maybe you could possibly learn something by collaborating with David. Hell, maybe David doesn't know shit. I do know that I've followed what his books state and my street motors prior to all this turbo stuff were faster than all my friend's.
Thanks DV for all your help.
I just figured it out. David is the "Alfred Hitchcock" ov engine tech guys! No insult intended. Rather a complement.
DV has forgotten more about engine dynamics than I'll ever have the opportunity to learn. And he also has a good editorial crew that can dumb down his knowledge in order for guys like me to understand his book
Thanks for sharing your knowledge. I really appreciate anyone taking the time out of their lives and opening themselves up to criticism which happens whether you are correct or not. I think the criticism alone is why many people aren't bold enough to share their experience but that's easy enough to sort out with more research. You can usually spot the ones who are being controversial just for the sake of it. Im going to take this knowledge you've shared and apply it to my next build. Why? Because it makes sense.
thank you for your time
Wow mr vizard thats telling them straight.
Full respect,
Thank you for your time and sharing your knowledge.
David did you ever see that TV show "Myth Busters".
They did an episode were they experimented with very very long PVC pipes that fitted ping-pong balls inside.
They brought the pipes to a close vacuum, with clear tape over one end sealing it.
They then pierced the tape and measured the speed of the ping-pong ball.
The ping-pong ball was able to travel at over 1,100Mph.
Braking the valve seat seal on a blue printed High comp engine must be sort of the same, as the above experiment.
Massively long time fan...I have a Kent 1700 244kent cam.
DV, thank you, excellent video.
As always THANK YOU for sharing you vast knowledge ❤
THANK YOU DAVID, I WAS GETTIN A LITTLE WORRIED ABOUT YOU BECAUSE I HAVNT HAD A GOOD VIDEO TO WATCH IN WEEKS I EVEN REACHED OUT TO ANDY TO MAKE SURE YOU WERE OK, IM GLAD YOU ARE OK AND THANK YOU AGAIN
Thank you for sharing your information David it has helped me greatly. I have only bought three cams so far but my experience has been identical to what you are explaining, all have been for sbm 1-110 and 2-112 it was completely night and day between them even tho it really should have had a 107. Again thank you David 🙂
Well done and spot on. Thx for sharing, David.
Top Information as allways Thank You
One more thing to add here...DV your comment on a marine engine that would suck water back into the engine was also outlined on the Engine Performance Expo channel by the great John Kasse on using old plain steel headers that had oxidation in them. Dyno shops use these and when a new engine sucks that rust back into the engine they blame the builder for not cleaning the new parts and wiping out all the bearings!!
Thank you David for your work
Thank you David. I've been a mechanic every since I was 12 years old. I'm now 64. That was not every day. Hahaha I would get pissed and do something else for a while. But thank you
Super job! Is there going to be a part II that covers dealing with the longer duration ext lobe. Am very much interested in that configuration. Thanks much.
Cylinder demand- spot on you have to have the intake opening compatible with the cylinder demand. Problem is you sometimes have to start intake opening earlier than optimal (because, as you said, once you get behind you cannot catch up) so you go to a higher intake valve angle and sink the valve this is after lengthening the rod to make max piston acceleration later.
WE found this out prior to 1962 and it is really obvious with a 4.25 stroke sbc with a 6 " rod early "fulie" heads and stock under 1.5 rockers
later larger lifters, larger cam tunnel and base circle, higher rocker ratios can be used to help,, none available in 62
Infact we had to use a small base circle to clear the rods i'll have to check vs 128 method but BTW cam ended up with 400 degrees at .001 Today it' just too complicated Just call Mike Jones you get more than what you pay for
Thanks for your vast knowledge and sharing it with others.
Highly efficient, raised port heads like Pro Stock, Yates, SB2, Blue Thunder, and 4 valve like a wider LSA to prevent too much intake charge from exiting the exhaust port during the overlap period.
Evan, you are not grasping the whole picture here. Don't forget the effect of theCR and intake valve acceleration!
I build 4 valve engines with nearly ideal port shapes, volumes and other parameters. The engines perform best with whatever LSA the dyno says. I use 1D software and model the entire engines before making model runs, and the outputs are amazingly close to dyno tests. Being DOHC 4 cylinders moving the cams around to change LSA is simple, so many possibilities are tried.
DV's method simply doesn't work on these engines because they are far outside of 2 valve SBCs - or any 2 valve engine - because of the much greater valve areas per displacement.
DVs formula is for a widely different type of 4 stroke ICE. My units more closely resemble F1 NA engines(15,500 RPM) than any 2 valve engine, hence the formula doesn't apply.
W O W ! ! ! David this information is dust from the cam gods table!!
Thank you kindly for your brilliant words!
Using these rules stated here (and other great DV tips i got out of his books) and I built a 416 Big block FE, followed DV's mild porting, relieving and scavenging and biased bowl work (all on my own time), and used a tight lobe cam, minimal overlap, advanced it as instructed with a degree wheel (turned out i had to actually retard the cam on the key because it was ground wrong!). Using the supposedly "garbage small port smog D2 heads" and stock S intake (knowing the intake would not flow over ~5500 RPM if i was lucky, but that was OK, i wanted mega torque, I was able to build a sleeper truck that with a three on the tree could smoke the tires in all three gears at will, and pull onto the freeway with a 3000# trailer in tow beating a BMW x5 with ease. With a longer rod we were able to cut the pistons and square the block to have the pistons a very slight + out of the block for a perfect quench with a typical stock head gasket. It was an Absolute beast, all stock iron. Go the same gas mileage on the hwy as the stock 352, but over twice the power if i needed it. Love your work and dedication DV!
What was the specs on your camshaft and the bore and stroke of the 416FE? I take it must be a stroker build.
I want to make one technical comment to this video. I don't think it was mentioned why the first 90 degrees of induction stroke is important. Due the the design of crank/rod systems in engines, the maximum piston velocity occurs around 75 degrees after TDC. The piston movement is what creates the depression that starts the air moving. If you haven't got the valve over 0.25 D lift by then, then you are likely losing out on induction efficiency. It probably affects the resonant tuning as well which will hurt you up top. So if you have a really large intake CL, you may be late to the game getting the valve moving by 75 ATDC. Obviously, if you have a four valve engine or a large valve/piston area ratio head like the LS or hemis you can get away with a relatively later opening because they generate far more curtain area at low lift. Chime in everyone if you want to elaborate or have corrections.
For over 30 years I've had an interest in cam design, and this video was the most informative and useful one I've ever seen on the subject. And it all makes perfect sense to me! Guys that blame their cam's low vacuum and poor driveability on its racy, lumpy sounding 107-8 degree LSA should actually blame their "bottom of the catalog page" choice of duration. I think a 350 Chevy could have great torque, vacuum, and street manners with a 106-107 LSA, if you limit the duration @.050 to around 224° or less. I'm guessing that would make for an overlap of only 40 degrees, off the top of my head.
Thank sir for this information, and I appreciate you sharing your learning work and energy to make a perfect product with us.😊
Thank you for sharing your knowleage.
Since you're so knowledgeable, I wished you made videos more geared to small import engines, for example the 4AGE series, specifically the BigPort 4AGE 16 Valver(4/C) or 4AGE 20 Valver(5/C) 4 Cylinder motors
Hi Brian,
I was not missing the valve to piston situation. I was intentionally dealing with the gas dynamics only plus the evidence that lead to the conclusions stated.
I would really like the opportunity to visit your shop. This is something I would like to plan for early June. Would that work for you?
DV
David Vizard claiming to be the world's premier automotive research engineer is like Stephen A. Smith claiming to be the greatest player in NBA history
Perhaps a rocker video is in order? Im fascinated by this series.
Amazing video. I had to stop and go back a few times to get it clear in my head. I have a question for your David. Can this formula be used on a 4 valve engine and if so what would do you think the number would be if not 128. Also i guess you would work out the area of the two valves them work it backwards to a single valve area and thus diameter, Thank you again
When i was a kid reading magazines and catalogs, i saw cams for a SBC, 265-400, i was thinkingh, how can a cam for a 283 work in a 400+cid, it cant the correct, for both enginrs! I learned they will all work, being at varying degrees of imperfection!👍
great stuff! Thank you David!
since LSA's are much more advertised than LCA's, do we have to assume that the cam manufacturer already came up with the appropriate LCA? the biggest criterion DV established here was how to NOT screw up the LCA; that a late LCA is Death to power
i think most every car guy cam change is done simply without the setup to adjust the cam timing, complete with dyno results, so whatever came out of the box has to work with the standard sprockets and timing chains. logically then, if some companies don't get this right, they should not be in the cam business, IMO of course.
and thank you DV for explaining this so thoroughly and well!
You picked up on my point there. We should not be buying cams from a cam company that is not on top of the job.
Hello Mr. Vizard, hoping the day finds you well! I wanted to thank you for making this information known, and for your countless hours spent pursuing this information! I had to think overnight, and am going to limit myself to 2 questions. If you find time to answer them or not is entirely understandable! My 1st question pertains to overlap. You used a 10.5 to 1 compression 350 for an example. If I were to use the same engine displacement and cylinder head, but lowered compression to 9 to 1, would it still make sense to have lsa around 108?. I would use less intake duration to build cylinder pressure back, but that would also result in less overlap. Second question: I know you mentioned less compression-less lsa, but is there any good way to determine this? Thank you!
@ David Vizard.
Thank you sir. I'm pretending to understand all this information. I've been a mechanic for 40 years. Born in 68. I wonder if you knew Zora Arkus Duntov? Did he share such knowledge and a place of one of the few on the planet?