The truth about LCA's Vs idle & vacuum quality
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- Опубліковано 7 лют 2025
- In this, Episode 143 DV talks of the misconception that still are common place even after viewers have watched the ground breaking video showing how it is possible to accurately calculate the LCA a cam needs to be to suit a specific application to within about 1 degree.
In this current video DV recommends you watch these three video’s (links below) to get a better handle on what is going on here. Episode 85 is the real important one but the others also focus in on other details needed to spec a cam correctly
Episode 85 • Hyper advanced ProStoc...
Episode 93 • Big Torque with easy P...
Episode 115 • Over 90% of turbo cams...
So a few months ago, I decided to try some of David's theory, and I had a custom cam ground from Bullett for a SBF. It originally had a 5.0 HO roller cam, which has a wide LCA. I ground this cam on a 106, with similiar duration and better lift on a hyd flat tappet camshaft. It idled good, basically the same as the 5.0 HO roller cam, but had a crap ton more torque down low. Up higher in the RPMs I dont think it lost anything compared to the 5.0 HO cam. I really liked the way it acted, especially with taller gears etc. Before it wouldn't do a burn out. After the cam swap, it would light them up, same trans, same stall, same gears. Putting every cam on a 110 is a cop out. off the shelf strategy. I love tight LCA cams, and most people dont really get it. Thanks David V!
Mr. Vizard, I used your cam choice information when building my 408 Ford. It idled about as smooth as a Toyota Camry at 800 rpm, and with 13.5 inches of vacuum. Power was 607 HP at 6500 rpm, and 546 TQ at 5200. A nice little 10.5 to 1 pump gas street engine I could drive every day.
What heads did you run on that 408
Very nice. What is the LCA, lift and duration for both intake and exhaust on this camshaft. In other words can you please provide the cam specs. I really like those results.
@@carlclark989 EDL 7721 2.125/1.625 with mild porting to keep velocity up. They flowed 355 @600 but the focus was on mid lift numbers
@@captainrawn it was a Comp 35-772-8. 286/292 248/254 .614/.621 110 LSA. Page 78 of the catalog. Slightly off, with a bit too much duration. It was during Covid and everyone seemed to be having cam core issues at the time. I felt it was close. Being a solid "street roller" I felt it gave good ramp acceleration rates and stability without having to check the lash every time I drove it. Knowing what I learned, I didn't need that much cam, but it's what I could find used at the time. Maybe 8-10 degrees less duration would've been ideal for what I wanted out of it, and I might've made roughly the same power. I had EDL 7721 heads on it since the cubes were so much higher. Big block sized cubes should have appropriately sized valves and flow. The 396 Chevy BB has 2.19/1.88, but we have better knowledge of port design these days, so I thought the 2.125/1.625 would be good. The more accurate the head choice for the combo, the less cam duration you need to compensate. Velocity, and port and valve size should be appropriately sized with the airflow demands off the cubic inches and stroke. Except for the Boss 351 engine, Ford has always struggled in this department until the Coyote engine.
@buildaboiworkshop A little bit, yes. Brakes worked fine though. A little too much duration, but nobody I contacted had cams and it's what I could find used that was close and nearby.
Mr. Vizard is on the know, I got one of the how to build books when I was 16, the first Chevy 350 I built I used the extreme amount of knowledge and did a lot of independent research asking engine builders their take. I had limited cams available to me being in Canada so I chose what worked closely to the Vizard formula. The engine pulled so hard it would keep pace with a motorcycle from a stop light. If I could I would love to sit in a class. Thanks for sharing Mr. Vizard.
I had a 1970 malibu with the 300 hp/350. As a young kid we did a dingleball rebuild, and we installed a Engle rv10 cam. It was 210/210 .440 lift and 108 lca. With just that mild cam, and headers. Turbo 350 and 3.31 gears, people couldnt believe how it pulled! That sold me on short timing for street driving, and 108 l.c.
A 210@.050 on a 108 is the perfect cam for an otherwise stock 350 engine in a street car.
@@robertwest3093Exactly what I have in my 350 astrovan pills like a team of mules...
Going to put an Rv10 cam with 106 in my 225 slant six. Similar specs to what you describe up here. It needs it even tighter..I can't wait how this little stroker will rub with it's headers and reworked head
I love Engle cams
My 1st experience on LCA. Was 39 years ago. A friend of mine worked for John lingenfelter and got me a cam for a street 383 SB CHEVY. It was circle track grind and had 108 LCA. For a street stock. My friend witch is the engine builder said we'll it's going to blow the tires off. I said great., I'll take care of hooking the car up. All of them knew I was going to tune the carburetor to get it to idle smoother
My friends and I have been taking David Visard's advice for building performance, SUCCESSFULLY since the 1980's! He knows how to make power.
Excellent video David. My minimal experience aligns with what you are saying. Most of my experience is with old Cleveland's and cast iron heads. Through trial and error, i ended up with much greater LSA's than the cam grinders were happy with. Interestingly enough, many years later i bought your How to Build Horsepower book and based on your recommended calculations, I was within 1° of where your recommendations said I should be. I got there on luck and money, wish I'd bought your book many years ago. One thing that I have worked out is that most of the people that you talk to at cam grinders are order collectors, and salespeople, not engineers or engine builders. Many thanks Greg
Clevelands are a different animal. Most never realized that and caused them great confusion.
@@psychoholicslag4801 agreed. I've always said that the greatest weakness of a Cleveland is Team Small Port engine builders
@@theshed8802 😄😄 so true.
I am building a roller 302 2v OC Clevor, and decided that the stock HO cam @ 115 LSA was close for a street engine. I am doing weird things to it to get 10.5:1 with flat top pistons. I think ideal was around 114 according to the 128 rule.
@@stuartwall8212 you need to buy David's book and read it. Fords use 127° as the baseline
I don’t know why the trolls are questioning this DV. It’s worked for me ever since I started using it and it has worked for many other people.
FINaLLY someone who knows what they are talking about! Been saying this since high school of course I read some of your books in highschool 😂👍👍 thank you Mr. Vizard
This is why I went for a 227@50 with just over 11 to 1 static comp instead of high 230s to 240 degrees @50. With a 109 LSA.
sounds like a good street cam. 🤠
@DANTHETUBEMAN that was the whole point of it. With that cam and the calculated 11.15 static comp it works out to be 8.5 cranking compression. Perfect for E10 fuel here In Australia with a tight. 040 quench. The .006 cam duration is 277 289. Should run from around 2000rpm to about 64 6500rpm power curve with peak torque just under 5000rpm with the intake track being about 13" long and DV inspired exhaust system with street legal sound open header power.
@@lcxu1051 vary smart build, vary fun to 😁
@DANTHETUBEMAN I know it is. Funny thing is the engine shops here in Australia disagree and say it won't work. I grew up around racing my whole life and never knew DV or any of his ideas. Only learned about him about a year ago. What he talks about and says is exactly what I learned from my dad growing up with motor racing.
@@lcxu1051 DV is not selling car parts, so there is no salesmanship on this info, he is telling the information he learned out of flow bench testing and racing, he has a great software program now he sells, but that's a tool he developed out of years or testing.
How about giving us Pontiac guys some love!! Love to hear how your program works on 400 Pontiac!!
I think there's a fudge factor in the 128... 126 ? I don't know.
Even if you're off a couple it's better than the wide LSA the cam companies push to you
I have been asking him for over a year to talk about Pontiacs, from what I read he worked on them back in the day.
Come on David show us some love!!
Probably not an interest in them blocks,,for David@@mikemcnamara2943
Check his books.
"How to Build Horsepower "
Should give you a more generic way to get there (or close) based on valve size vs cylinder volume. Then adjust for compression and other things. I have used this for everything from a pinto to 496 BBC with good results before he had refined it to the "128 rule" although I have been out of performance arena for quite a while.
Thank you , david , you keep my wheels spinning and the Ideas flowing, you are on my Mount Rushmore right next to smokey.And just ahead of grumpy
David "the Cam" Wizard...I mean Vizard. He actually knows what most think they know.
As always DV. I want to say thank you. For sharing your god-given wisdom. 😊 You're always right on top of things and you know the truth because you've been there done that I think I told you before but I'll tell you again. 😊 From your books and I got a few of them. You put me in the winner's circle. August 7th 1999. I build my engines in my one car garage. Unbelievably my car number was. 50.
Hi David, your Mod’ Mini book is still my prize possession after all these years. Regards from Olde England 🏴🇺🇸🏴
🔔😎
Street performance "sleeper"... DV cams have been kicking axe for many years.
(It cant run that good, it idles too smooth 😁)
Well... if I ever seem to have some luck that's not "bad", and am able to get some money together again, I'll certainly be using DV's camshaft formula! Seems to have a pretty good reputation out there, and I have no "issue" with anything I've heard him say before.
...and his porting vids and such are GRRREAT! I've been messing around with "hot rodding" all different stuff for 30 years (my entire family is into it, too) and he shows some things that I certainly haven't thought of doing that I REALLY want to try now. Unfortunately, life turned pretty bad for me, and just getting out of the mess (hopefully) and back on my feet again...
I'd LOVE to be able to pay him to port the head for my 2.3T '87 Mustang project that I started on forever ago, and can't afford now...
ANYWAY... I truly appreciate the effort made by the "Powertec 10" crew, regardless. David has no obligation to share any of this with us, yet he chooses to take the time out to do it. I think that's AWESOME.
In a short video you did a good job explaining the duration factor. I need a high lift, short duration cam for my jeep for high torque, now I need to learn how much lift would be appropriate.
Thank you for saying it straight.
Thanks DV. For sharing all your wisdom
Thank you Mr. Vizard. I think you've mentioned cam companies are under pressure to supply "too big" of cams for the application due to customers being greedy for power. So they spread the lsa to kill some overlap. But then the cam ends up being a little lazy, especially in low and midrange. Thank you for cutting through the bull!
Way back in either 81 or 82 when Competition Cams introduced the High Energy 268 for small Chevy's they ran a huge ad campaign so I bought one and believe me they were high back then, paid 125 bucks which was a lot! Installed it in my 78 Z28 that I bought new which by this time had headers ,dual plane intake, "legendary" 350 hp 327 copy cam , still stock 8.5 compression and stock converter and would run 15.0's with that combo. The original 268 H.E. had a LS of 108 with 218 duration and was pretty choppy but worked fine and it knocked a full second off my E.T. down to 14.0's with no other change. It lived up to it's hype and i was ecstatic but I guess they felt the need to smooth it out and it wasn't but about a year and the LS was moved to 110 which is the Comp Cams norm now.
Agree completely, bit want to add one variable. That is cam design. Two identical cams on paper. One may do nicely on the idle quality, the other will chop at idle. The acceleration and deceleration ramps on the cam play a role too here.
Hey David I remember Crane had a cam for small block Chevys, that was close to stock specs but on a 104 lobe center, made tons of torque for a 4×4, were you involved in that, probably the 90's, good video again David!!
Have a 355sbc. Edelbrock aluminum heads, Edelbrock h122 blower. 850 blower carb.
9.25 static comp. 8psi of boost. In a 3200lb car. Picked a dougherty cam. 228/234@50 535lift 114lsa. Idles very well, lots of vacuum 18 at idle. Pulls hard to 6500.
Had a comp 230/230 @50 515 lift on a 110 lsa before did not work nearly as well.
it's the smaller intake duration, bigger exhaust duration, you are forcing air/fuel in, you need more outflow, that's what the second cam is giving you. 😊
you can keep the same durations, and go down to a 108• lsa
and get more Torque. 🤠
@soldierbyname
Is that what's in the C3 in your video? Do you have any other footage?
I only ask because I'm going to be installing one in my 1971 Camaro this spring and it's hard to find any motivational videos with that supercharger.
Thanks 👍
David Vizard, man, you are the master, I really appreciate your time in helping us, your experience is very precious.
30 years ago I built a 383. Chevy 10.5 compression 248 ' @ 50 duration 108 lca. Power brakes worked excellent. Don't know why people crying about vacume.
I keep thinking of my Harley Sportster, it has four cams one lobe for each valve, one could change the lobe center line by shifting the intake and exhaust cams gears with each other. One would have to check the valve to piston clearance closey first. It would be a very interesting experament.
Yea bro....I wish he would derive a constant for Harley engines! It’s doable, but DV may not want to allocate the time needed to do it. It would be nice because Harley cams are marketed by totally different specs than hotrod car cams.
As always your videos are doing us a great service...thank you very much for your hard work sir..
Wish I would have known, I just installed a nsr truck norris cam for the ease of it and the hype. 4th gen 6.0 ls with 823 rectangle port heads terminator x max and 4l80e in a street 1994 s10. Also, I’m building a 1st gen sbc 383 10.5:1 cr with TH400 and 4.11:1 gear in a 1989 rx7. I bought the Lunati voodoo 268 cam 110 lsa but I will not be using it and will be using your lsa method for the cam. Maybe I will compare on dyno and look at average power. I hate learning the hard way and wish there were more research and development in the right direction like this.
Your videos are great and super in-depth. I really enjoy them!
Thank you, DV, for your logical explanation of one of the most misunderstood camshaft parameters, LSA!
I think you're great, David!👍 Don't worry 'bout them other guys, too much
I have seen cars that run good have cams that fit near the DV profile recommendations. Read the book!
🙏Please do a focused video for the Cleveland on this topic. We are always neglected due to its not a pop topic for the big money makers, yet It is an incredible foundation for one of the greatest of all time Engines.
Thanks David for all your time and sharing the no bs knowledge!
It is greatly appreciated. 😎✌
Thevacuumed. Principals are the same that apply
Looking forward to examination of what the LS likes as a constant. It deserves attention primarily on account of valve angle and its effect on scavenging? Unwinding many decades of Stroker McGurk theory seems to boil down to this: many of us in the past accepted wider LSA's... thinking bigger duration was the ticket. Better spring tech these days gives us a nice helping hand: with higher lift possibilities, a return from wide lsa is not a punishment at all.
I wish I would have known this years ago. I called comp for my Dually Vortec 454. I asked for an aggressive towing cam and they gave me a 01-412-8 Xtreme energy. specs 264/270 duration .510 lift and 113 LSA. with mild ported head, headers, exhaust, intake, injectors my tuner couldn't get it to idle any lower than 950RPM. It ran ok but low end seemed to be lacking.
Tow vehicles don't like lots of compression to much chamber heat or duration
Nice, looking at getting rid of my superram intake and going to a carb on my C4 Corvette.
Many years ago when I was first learning about cams, the rule of thumb was more overlap, rougher idle. Maybe what changed is all of the programs out there to compare and design cams for max HP making people focus on LCA.
40+ years ago I changed rocker ratio to aluminum 1.6 with better springs and mildly ported heads on my 69 Z28 which pick up .2 in the the 1/4 with a 4:88. Did even better when lunach was work out. My point is that the factory cam was dam good and rockers gave more flow ,old Indy engine builder show me this when I was in high school and all he stressed was port velocity at points that impeded flow
Long time subscriber. Currently waiting on the LS constants. I believe your system works. Keep up the good work.
My problem with this theory is the best cam for a road car is the standard one it came with, if it's a race car with a 4k rpm rev. range from 4-8k if it's a 10k rpm motor that's 6-10, if it's a single seater 8-12k.all requiring very different profiles. In the case of the Nissan infinitely unit that used on ovals over there they had a 600 rpm difference between down the straight and around the corner. Experimentation was 1deg of cam duration at a time.
At that level after 6 months of testing there is only one answer, for every thing else there seems to be many.
Piper cams in the 80's had their HR2 range which had assymetric profiles on opening & closing ramps. Brilliant and logical idea which lasted 10 ish years before reverting back to conventional equal flanks
For new cars? Yeah 100% anything from the 50s/80s? Probably not especially with ported heads, bigger carbs & headers. Also cam knowledge went far!
I think the biggest reason people tend to dismiss the LCA being so important is they fail to think that having the point at where the valve flows the most in relation to the piston speed is not important. If you run a big duration with a lot of lobe sep your peak intake valve opening might be occuring as the piston approaches BDC and that will only be ok at extreme rpm everywhere else it will be killing you as the cylinder fill will be almost entirely dependent on inertia and it will be highly prone to reversion.
Thank you David.
id love for DV to spec a ls 5.3 cam specs with standard heads 7g rpm limit. i would think it end up in the 108-106 LSA area the duration would be intresting.. and say just go dyno headers, and 750 DP on a vic jnr
You the Man 🙌 God Bless You DV
I love your 128 formula! Is there formulas for choosing the correct duration & overlap? I'm struggling to choose the correct cams & really really want to be able to get it correct. How exactly do I get your program & how much? Chevy gas & Cummins diesels are my prefered builds. I was so looking forward to watching & learning from Jacque & her point of view. Must have been amazing to have a father with so much love, knowledge & wisdom to teach & share daily! My grampa raised me, male pecking order was God, Grampa, & John Wayne.
Waiting on the Cleveland constants...please.
Read his book and how he adjusts the LCA for big block Chevys…. Canted valves need a slightly wider LCA compared to inline valves to keep parody. v/r wh
BTR would agree with you DV looking at their grinds for the Ls world.
Up to the minute technology? Your how to build HP book is over 20yrs old! That’s antique in the motoring world!!!
Can't wait until you can get Mopar engines in your program!
Poly POWER! 🎉
I'm no genius, but I agree with this presentation 100%
LSA=128-(CID/8/Valve Diameter X .91)
For a 355 SBC, with 10.5 static CR, with good heads. Change variables, such as CR, valve size, CI's, etc, and there are adjustments that are needed. All clearly laid out in his book, which I recommend to everyone. Great info.
Years ago, I swapped cams from an Isky Mega 270 (221/221-108) to a Crane 216/224-112 due to the hype about Fords needing the duration split. Couldn't believe how much slower the truck was with the 112 cam.
Advance it. Or put more gear ⚙️ to it!
Really enjoyed it as always thanks
I can't wait for this video!
What video is that?
David can u explain why the LS 5.3s and 6.0 engines are on a wide LSA? I think there on a 117 or more. In my opinions they did this for a smooth idle. High vacuum and have a broader power band? There duration is short for the street. A narrow lsa always has a rougher idle and less vacuum.
It all seemed so simple to me, and perfectly logical! We've always known that LESS DURATION = MORE TORQUE. LESS OVERLAP = SMOOTHER IDLE AND DRIVEABILITY. So where is the disconnect. The overlap determines the idle quality, not the LSA!
I think everyone wants solid roller high lift numbers in a hydraulic lifter engine.
in the 60's people thought Chevy was going to wider lobe angles for better idle,
LESS IS MORE allot of the time..
I ran a Comp 284xe with a 110 degree lobe separation and 240 degrees duratio in my big block Chrysler. I wiped out a lobe after about 5000 miles. I replaced It with a mopar purple cam with 114 degrees lobe seperation and 248 degrees duration. Both Cams pulled the same vacuum at idle. The Comp cam was way more responsive, but the Mopar cam pulled harder in the upper rpm range.
It was bigger, it should have
@cedricwilson2055 I'm not sure if I understand.
Bigger the LSA 114 the Longer pull
I’m a big fan David but I’m confused by your comment that said the cam vid was for BBC/SBC , and Ford Windsor but not Cleveland engines due to their canted valves , how do they differ from BBC’s canted valves ?
Cant wait for LS info.
Using your 128 rule I come up with a cam that no one makes (223 on a 108). The gospel in the LS world is manuals want 112deg of overlap and autos want 114. Other than that it's all about what stage cam makes the most chop *face-palm*
Most likely your favorite cam manufacturer will make it for you if you give them a call (and probably a few bucks more for a custom cam). Well worth it.
@@Staypuff777 I'll have to give that a try. With Dave's formula I can get LSA and intake duration. Ive heard him say lift is valve diameter × 1.3, but still haven't nailed down exhaust duration or what intake centerline should be? (How do I know where to degree the cam?)
Sir first I would like to say hello and thank you for all of the knowledge that you share my question is have you ever done any testing of the 60 degree v6 chevrolet engine?
Spot on, David!
DV would love to see some of your knowledge working with gen III HEMI. Huge community that could use expertise.
@David Vizard
Will you be adding the Cleveland parts to your Program the future??
Hi David, great video as usual. Had a question, can your program be used with small competition go cart engines? Note some of these are multi cylinder these days. Was just wanting to know if your program scales with size. Thanks!
What about the BB Chevy with long and short ports? Different cam timing for short vs long? Different diameter exhaust pipes? Different ratio rockers?
G'day David. Do you have a number for the 2V and 4V Cleveland to plug into your Cam formula? Or is 132 that you use for big blocks sufficient? Regards.
Should we calculate required duration or lobe separation angle first? Also, all else equal do higher compression engines idle better with the same overlap?
Can you specify how much overlap is needed for reaching certain RPM limits? (Say for 5,000, 6,000, and 7,000 rpm). Also, how much overlap do you recommend and for what parameters? Thank you, Mr. Vizard.
just do a Google image search for
vizard cam overlap estimator chart
I’d post the link but youboob will delete it
it’s in his book, which you really should biy for all the finer details, but basically
10* - 40*….towing
30* - 60*….ordinary street
50* - 75*….street performance
70* - 90*….street/strip
85* - 100*...race
95* - 115*...Pro race
@@nobodyspecial5026are those overlap figures @.050?
@@nobodyspecial5026 these numbers look like they’re at full duration, say 0.006” lift, not @0.050” lift. Correct?
DV, I would love to hear your input on the Gen 3 Hemi platform, specifically the 5.7 "Eagle" 10.5:1 engine with stock heads. Several companies have flowed the stock Eagle heads so I won't go into that here. They flow pretty good, for a stock cylinder head. I want to change the cam in my 5.7 and am leaning towards (one of very few) a 108* LCA, offered under the "El Chapo" label from Scoggin Dickey Performance. 215*/221* on a 108* LSA, with .587" lift I & E. Application is a street-driven, daily driven Challenger with a 6-spd Tremec (unlimited stall 🙂) and 3.92 gears, which gets it rolling in short order. I don't chase horsepower numbers. I know that it's torque that does all of the work, so I'm more interested in power under the curve. There will be a HP increase, just by getting the stock camshaft out of there. :)
Your right David. Example would be Diesel engines. Turbo and non turbo. Have different cam specs than gasoline engines in today's cars and trucks. A good example of a good cam would be your turbo mustang. It has an adequate cam. It can be better yes. Yet what are the specs of that cam?!
Thanks DV!
Great explanation David. What do you recommend for overlap. How do you determine how much overlap to run?
Does any cam-company utilize the DV formula for the L98 TPI or by those alleged TPI specialist for those of us who don't know Sht from Shinola about cam stuff????? Apparently, from how the legend goes, the factory intake & heads can't flow anymore for a bigger cam..... And if one of the hi-flo intake/manifold/head packages are used with a stroker kit at some point, what cam company will utilize the DV formula to custom grind a cam?
David does your cam software work with other types of engines? Vw flat 4 for example.
Another great video!! Would love to see video on valve seat cutting and angles and seat
dimensions. Thanks DV!!
Yes it works for vw motors, i used this in my cam decision to get what i needed... put me right around 230@0.050 duration which was smack on... from there pick the total lift for your heads and compression to give you what you need
I'm keen to know if this works for VW Flat4 aircooled engines too. I've read cover to cover DV's books and applied the LCA formula. But I think a piece of the info I in put was not quite accurate because I came up with a LCA exactly as the general production cams which never change (108). But one VW engine builder is often using tighter LCA.
@@mathewboyd3746 yes essentially its going to be 108 for most, the overlap is going to be the main difference in setting duration; CB makes theirs on a 107; you can always advance or retard the intake centerline to get it where you think it should be.
The way I see it is way too often a cam with too much duration is selected. The customer is thinking more is better and too much is just right. They have no idea of the many processes going on in a running engine to effectively the cylinder and then cap it off before the charge is lost. That to me is the major if not sole purpose of the cam.
Agreed. And as David points out, for a given LSA (LCA), too much duration results in too much overlap, and poor idle, low speed torque. The big cam companies know you'll pick too much duration, so they broaden the LSA to lower the overlap. Wrong way to pick a cam. The TMC program will calculate the LSA, you pick the overlap, and the duration, and that specifies the valve timing fully. Only thing to spec out is the max lift after that, and the aggressiveness of the lobes.
@@pete540Z exactly
Hello David, will your 128 cam program formula need to be modified in order to calculate the proper LSA, to be used in a 1969 Pontiac 400 Ram Air III automatic Firebird, that will otherwise be completely stock except, +.060 Bore (4.180 X 3.750) ported heads, and 11:2 compression? I intend to use only 98 Oct leaded gas. Thank you...👍🏻
I used 128 formula in my Pontiac 400 and bought a camshaft with 106*LSA with proper overlap and duration, like DV has been suggested.
GREAT JOB DAVID THANK YOU
Thanks for sharing 👍
Hi DV, thanks for clarifying - great topic!!
For IR intakes on your typical sbc ie; quad Webers or 8-stack EFI - does your 128 LSA calc change? (I’m assuming the 128 constant was developed for single plenum intake data)
regards, Brett from Australia
Jim Leineweber of Harley camshaft fame told me probably forty years ago now that he had never found a intake opening that was too soon. I'd never heard that before or since. This has nothing to do with what David is saying about intake lobe centerline. David is the leading authority on all of this as far as I'm concerned.
I want lots of torque from 1500-5200 rpm. I have a Pontiac 469 (.060 over 455) with 2.11" intake valves. D-port heads are pretty much flow limited at around .400 lift. The 128 formula tells me I need a 103 LCA cam. Is this really the way to go?
Then what benefit does having a wide LSA? Maybe it has to do with cylinder bank angle on a type of engine. The actual LCA on the shaft of the cam has to match the engine bank angle ?? I think some emgines like Pontiac low rpm high torque engines do better with a wider LSA?? while a Ford 302 high revving engine likes shorter LSA??
Can you provide a factor to use with a 10 degree canted valve head, specifically a viper engine?
for HD use you need to keep the valves on their seats, to cool, to live
as you said it's valve events seat to seat. duration
lca is a by product, whatever it is.(IMHO)
In a way, we almost can't really blame the cam makers for not selling the best possible cam, most of the cams are going into stock head and bottom end engines, most even with a stock intake and usually generic a long tube header. The manufacturers never designed those engines to make power, they were designed with emissions and fuel economy first and the power was just a side effect. I always took it as them selling a less than optimal cam on purpose, they want to give just enough of a power gain to get $200-500 out of a customer and I feel that they leave the extra power on the table so there is something they can sell someone who wants to pay more and get as much as possible. I always felt like they didn't want to get beaten on the street or strip by the average jackstand jimmy who didn't have to drop all the money on creating an optimized program. Maybe I'm wrong and these dudes really think they are selling the best they have but, I doubt it. It's the same as GM selling so many 4.8 and 5.3 engines that were designed to squeak through the fuel economy and emissions testing yet in the real world you could probably get the same fuel economy out of a 5.7 or 6.0L, it wouldn't have cost GM any extra to just build 5.7 or 6.0 engines as the base and put them in everything with a 6.2/6.6/7.0L as the upgrade engine/HD truck/supercar engine, who knows why they did it all these years and didn't give the customers the best they possibly could have. That seems to be the way everything is, the world is full of bean counters, greedy executives, non-enthusiasts and non-scientists. I blame DEI programs that promote and hire based upon immutable differences rather than intelligence, capability, experience, work ethic, passion and qualifications. Diversity never existed before and was considered dangerous to societies of the past. You will not do the best work you can to improve the future for people you don't care about who are dissimilar to you.
David, I am working on a 305 Chevy for a boat. How much lobe separation should I use without breathing sea water into the engine at idle?
using watercooled and not very efficient exhausts, brand Mercruser
even so, I want to do my best
6th, I’ll take it. Still a top 10.
Who would you recommend to make a cam according to your teaching
Some of us gearheads have our Harleys and love cam upgrades, any way we could get a formula constant for Harley Twin Cam engines?!?
Hello mr Vizard, i would like to say thank you for youre educational videos. Ive learned quite a bit all thanks to you sir. On that note id like to ask you a question. I have a 91 mustang gt 5.0 5spd. Im looking to do a complete top end kit on it. Im looking to get the most i can out of it as well as still be able to drive it on the street. My issue lies in cam and head selection. Do you have any cam recommendations along w rockers and heads? It will be street driven w a few red light races lol. If i need to get ahold of you thats ok too. I wish you would do 3 builds on a 5.0. A budget, a mid tier, and a high end. I also wish you showed us how to port a set of aftermarket heads for it as well. I know its a tall ask as im sure youre a busy man. I wish i knew how to build engines let alone build as good as you do. This is my first project car that im having fun with. I know you said the lca is critical along w other cam specs. After seeing youre cam designs i prefer what you do. Does a good off the shelf cam even exist for these engines? Any help is appreciated and i look forward to seeing you build a high hp and tq 5.0l sbf engine. Budget friendly would be super awesome. I still have the original 5.0ho engine in mine ill be working with. From what i understand my engine is the roller engine. Again any help is appreciated and thanks in advance.
What effect does CR have on LCA?
Thank you - Looking forward to the Next Episode!
the formula is considering 10.5:1+/- a point or so. lower compression needs tighter lsa and more compression is wider
Take a flashlight and a screwdriver and go look at it.
Disregard
I have a book on tuning Weber carburettors and it gives suggested idle speeds depending on cam duration, lower duration suggest lower idle speed and higher speeds for longer duration cams.does that align with the information in this video?
Have ya produced any of the powertech 10 T shirts?
How do you find the correct duration? I think I am doing the formula wrong when it comes out close to 270.
Thanks David. Could I use the big block Chevy constants for the 351 Cleveland ,for approximation?
107* Thumper works great in our 351C... But it is lumpy... But gut busting torque.
@@hotrodray6802 hi Ray, I’m using 108 right now 530 lift. I don’t remember the duration. (No cam card in my office it’s in the garage)
What changes would you recommend on middle sized Cleveland engine. BB Chevy is also canted valve. Same changes to cam?
How do we get a hold of the DV’d cam choice program? I’ve searched and searched.
How do I determine overlap?
exactly why im using a ramjet cam in my 350 vortec build, with 1.6 rockers. 196/206, 109 lsa, 105 ICL. with 1.6 rockers, lift is .460/.480. -17 degrees overlap
Not really sure what the issue is. It works just as stated for the specific reference engines. Other engine configurations just need to be figured out to achieve the same is all.
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