He has that “Radio” voice.
Does this prove David Vizard's 128 lsa formula ?
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Yeah, it's like "Just sit back and let me tell ya a tale bout camshafts and morons that pick the wrong ones..."
BTW... i have put together a few motors in my life but cams were mostly a guessing game.. even if Davids formula isn't perfect i feel better having a guideline to go by
Wow, I'm glad I chose a Isky E4 for my 273. That som' ***** puts out max HP and doesn't leave anything on the table !!! Oh ya, 108°
I agree on both statements. Camshaft LSA is sometimes not about the most power obtainable. If it doesn’t idle the way a customer likes, it’s the wrong cam. Even if it is a proven power maker. The customer must like what he hears as well as how the car performs.
I’ve done some jobs where the car own hates that chop chop chop sound. Others just want that smooth idle and high vacuum for there power brakes and easy pedal driving response. There not after max power, just a feel good drive.
When the 128 formula came out, the only thing I put down in print was it’s a formula that doesn’t cover everything and can’t. It’s because of individual taste and likes. Nothing about it being correct, the best, etc….
Nothing more, nothing less.
.75 , for 8.5:1 cr you would add 1.5* to the lsa.
Edit* meant minus less cr tighter lsa.
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You'd think.
I'll play around with the formula. If it comes up with something similar to what I would have chosen based on my experience and "little bit" of knowledge I have, I'll use it. If not, I'm chosin my own junk. I haven't missed yet.
I've got all his books, I'm not knocking the guy, I'm just not seeing the evidence that his formula is gonna give most optimal results, I'm sure it does ok, and I'd probably use it to a point, see what says for your combo and keep that in mind as choosing a cam. But if you look at what it says for a 340-416 it recommends 109-105 pretty much what people know they would have to run if they wanted a more serious cam for these engine.
The I do like is the basic idea run the better lsa and compromise on duration, so basically if you gonna run a 108 vs 110 lsa you would run about 4 degrees less duration. Which to me sounds like it make sense especially in a street car but there's no proof on that.
But eg.. Low cr 318 the formula say 105 lsa, and say we keep with AJs 48* lvc that would a 254 on a 105 lsa sounds like it would work compared to say 270 on a 113 lsa would have same over lap.
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33IMP
Well-Known Member
I have not read this thread, but.... to my knowledge, DV's formula usually arrives at a number with a tighter lsa than most.
I have a (old!) Cam Dynamics sbc solid roller I wanted to use. Unfortunately i couldn't in my app, (5.7 rod, 406) cause the rod hit the camshaft in a couple spots. (NOT the cams fault, long rod 400 usually needs a smaller base circle cam.)
Upshot of this post is.... the cam was ground on a 104 lsa. I've never seen one tighter. I bet it would have sounded nasty at idle!
I have a (old!) Cam Dynamics sbc solid roller I wanted to use. Unfortunately i couldn't in my app, (5.7 rod, 406) cause the rod hit the camshaft in a couple spots. (NOT the cams fault, long rod 400 usually needs a smaller base circle cam.)
Upshot of this post is.... the cam was ground on a 104 lsa. I've never seen one tighter. I bet it would have sounded nasty at idle!
I meant subtract, I my head I was thinking add to the tightness, as for .75 vs 1, 1 supposed to be an easy rule of thumb way, then there also points for rocker ratio.
According to DV you should be 110, you over done it lolWow, I'm glad I chose a Isky E4 for my 273. That som' ***** puts out max HP and doesn't leave anything on the table !!! Oh ya, 108°
I think DV main point is sacrifice duration not lsa for street manners, which In a way makes sense tight lsa has good bottom and less duration also good for bottom end, Is it proven winner idk.
Since we are talking cams i have something that is bothering me... This is the first time i degree'd a cam.. usually just went dot to dot.. My cam from howards said to install on a 103, but dot to dot gave it a 109.. is it normal for a cam to be that far off? i checked it like 5 times to make sure it wasn't me. Emailed howards and they said advance it to 103 so i did.. been bugging me since though. (i should have checked more cyls)
33IMP
Well-Known Member
I don't think being that far off is common, but I can see tolerance stack up easily causing it. Cam pin, off two degrees (not much), Cam gear off two degrees, woodruff key slot off four degrees, you could be ten degrees off.... or they could cancel out and be dead on at dot to dot. Who knows?! (That's why you degree a cam for a performance app.)
Depends on whether they ground advance into it or not, it is commonly done, but not always. If they ground it straight-up, it wouldn't be uncommon at all, the intended advance(say 4°) + deviation in the timing set(say 2°) would put You off exactly that much. Even then, yes, sometimes timing set/crank-key/cam dowel or key tolerances can put You off that much.
If You did it right & double/triple checked it, You're good, if You want to check #6 to back it up go for it.
33IMP
Well-Known Member
Agree. But my next dyno session will be my first. I'm willing to bet that DV knows more about cams than I do.
(And just for giggles,I ran his formula for my 522 stroker Mopar, and a 540 bbc. The Mopar came up 101, the bbc at 104. I don't even know,if you can find a core that can be ground on a 101.)
What's lost in all of these drive-by/sound-bite takes is, DV clearly insists that every individual combo needs to dial the cam adv/retard on a dyno(or track testing if poss.), no matter what. Unless it is a known replicated combo already proven, it must be done, period.
It's not the easy answer everybody wants, but that's what it takes.
I'm not questioning his knowledge at all. I'm sure he's a legend genius. IMO, I just don't think something like that can be used as the blanket end all be all he says it is.
I would agree IF everyone was racing for points and money. Some folks just want to cruise and have a good time in something "peppy" and that kinda testing makes no sense for them. I'd be willing to bet that "they" make up 90% or more of what we're talking about here, too.
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Hence the formula, it is the best ballpark for guys running old iron, not shooting for a championship... it's just not the last word's all.
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