Does this prove David Vizard's 128 lsa formula ?

-
I've been doing some reading and stuff.

The formula used to get duration "LSA+ (overlap÷2)x2= Duration", is it used by many cam companies?

I noticed that the formula calculates with the same duration using the same 110 LSA and overlap as the multple different Comps cams that I checked, like identical.
However when I checked a cam from Hughes I don't get the same results. Also the cam from Hughes is a split duration cam, so maybe I did something wrong.
Also when checking the specs and stated idle and driving characteristics of the 110 LSA Comp cams, I feel the BS that I heard in the past about LSA was clearly somewhat BS. But I do see why people assume it's the LSA that is responsible for the idle and other characteristics as changing the angle of the lobes changes the overlap, but Comp Cams shows that changing the LSA is not entirely necessary and does it with different overlap.
Or at least this is what I can gather, but do correct anything I may have misinterpreted.
 
Ant said:
However when I checked a cam from Hughes I don't get the same results. Also the cam from Hughes is a split duration cam, so maybe I did something wrong.
Click to expand...
That equation can only tell single or average of a split, eg. 268/272 average duration is 270, so 110 lsa x 2 + 50* = 270
 
273 said:
That equation can only tell single or average of a split, eg. 268/272 average duration is 270, so 110 lsa x 2 + 50* = 270
Click to expand...
I see. But Hughes seems to still be a little different. Also I the formula works for @.050 lift too, which I checked with the cam specs from Comp Cams. So since Hughes only lists their timings @.050, I did a check and cam up with a duration number that does not fall in between the stated duration spec.

112 lsa + (-6÷2)×2=230. The duration spec is 216/220 for the cam. At first I thought it was the negative overplap throwing the math off, but the math checked out fine on another cam from Comp. Maybe Hughes is doing something different? That is how they feel their "real Chrysler" cam should be? Maybe I got something wrong?

I'm scratching my head, lol.
 
Ant said:
I see. But Hughes seems to still be a little different. Also I the formula works for @.050 lift too, which I checked with the cam specs from Comp Cams. So since Hughes only lists their timings @.050, I did a check and cam up with a duration number that does not fall in between the stated duration spec.

112 lsa + (-6÷2)×2=230. The duration spec is 216/220 for the cam. At first I thought it was the negative overplap throwing the math off, but the math checked out fine on another cam from Comp.
Click to expand...

Ant said:
Maybe Hughes is doing something different? That is how they feel their "real Chrysler" cam should be? Maybe I got something wrong?

I'm scratching my head, lol.
Click to expand...
Maybe their lobes are asymmetrical ? That might have an effect, seems like this equation is just doubling the overlap side of the lobes assuming the other side is identical.
 
Ant,
Did you bother to watch the video of post #298???
You will learn a lot. I keep mentioning D. Vizard. He was contracted by Crane cams to do cam testing, which is where the 128 condensed rule originated from his cam program. At Crane, he tested over 19,000 cam combinations! When I meet somebody who has tested more, then I will take their advice.....In the meantime,..
Why would you bother ringing a cam company? If the phone jockey was any good, he would be building engines.....not looking at a computer screen.

Richard Holdener [ you tube ] has also tested a lot of cams. About a year ago [ maybe more ], he tested 3 cams that were identical except for LSA. It is on the net. They were tested in an LS engine with EFI. EFI, another wrinkle. The cam with the tightest LSA, which I think was 108, made more tq & hp.....than the other two. Seeing a picture here?
Below is one cam page out of DVs SBC book.
It is a bit hard to read, but the important points are this:
- looking at the bottom chart, because it has more categories, Street & Tow to Real Race
- engine size ranges from 302 to 434
- note that for ALL seven performance categories, the LSA stays the same for the engine capacity. 302 uses 110 LSA; 434 uses 104 LSA.
- what does change for each performance category....is the duration. Both adv duration & 050.
For Street & Tow: 258 adv & 206 @ 050. For real Race 304 adv/245 @ 050.

img367.jpg
 
While yall are arguin all this crap, somebody couldda done built a motor, dynoed it, swapped cams out and got the best match doin it the old school way.
 
Bewy said:
Ant,
Did you bother to watch the video of post #298???
You will learn a lot. I keep mentioning D. Vizard. He was contracted by Crane cams to do cam testing, which is where the 128 condensed rule originated from his cam program. At Crane, he tested over 19,000 cam combinations! When I meet somebody who has tested more, then I will take their advice.....In the meantime,..
Why would you bother ringing a cam company? If the phone jockey was any good, he would be building engines.....not looking at a computer screen.

Richard Holdener [ you tube ] has also tested a lot of cams. About a year ago [ maybe more ], he tested 3 cams that were identical except for LSA. It is on the net. They were tested in an LS engine with EFI. EFI, another wrinkle. The cam with the tightest LSA, which I think was 108, made more tq & hp.....than the other two. Seeing a picture here?
Below is one cam page out of DVs SBC book.
It is a bit hard to read, but the important points are this:
- looking at the bottom chart, because it has more categories, Street & Tow to Real Race
- engine size ranges from 302 to 434
- note that for ALL seven performance categories, the LSA stays the same for the engine capacity. 302 uses 110 LSA; 434 uses 104 LSA.
- what does change for each performance category....is the duration. Both adv duration & 050.
For Street & Tow: 258 adv & 206 @ 050. For real Race 304 adv/245 @ 050.

View attachment 1716258672
Click to expand...
Those videos is what started this whole thread in the 1st place, all they show is tighter lsa generally makes more midrange torque (basically increases the tq per cid) but who is doubting that in the 1st place ?

None of them prove or even total disprove DV formula, but to me bring it into question that it provides the optimal lsa, it really only calculates lsa and no other cam spec, so it shouldn't be concidered a cam formula just an lsa formula, and it seem to pick a decent lsa, but not much evidence that if you go a few degrees wider or tighter than recommended that you'll lose 30-50 lbs-ft and not be picking cams like the 1% of builders and make 1.4 lbs-ft per cid like he implies.

If you want to use it to get a ballpark number, it seems fine, I'd would use it myself to at least know while choosing but I wouldn't necessarily limit my lsa choice to it's findings.

And I like his basic premise tighter lsa and less overall duration then people usually choose even there's really no evidence to say that's the best way.
 
RustyRatRod said:
While yall are arguin all this crap, somebody couldda done built a motor, dynoed it, swapped cams out and got the best match doin it the old school way.
Click to expand...
No arguin, just a conversation.

Also, gonna hopefully see what one cam can do for this guy. I'm betting not a lot of power, but good enough.

20240529_180810.jpg
 
Last edited:
Some people will want you to believe that D. Vizard 'invented' tight LSA cams & that they were never used in production engines. Not so.
The Morris Mini 850 engine came with a 230* cam [ adv duration ], 107.5 LSA. The low duration allowed for smooth idle etc. All of the BMC factory production cams were ground on 107.5 LSA.
Some factory high perf cams were ground on 102.5 LSA....
 
Okay a tight lobe sep may bring more power on a race car but not everyone has a race car.
Some of us like to drive our cars on the street and be able to live with them everyday!
Back in the seventies I had an Aussie Valiant Charger with a 340 six pak and four speed manual.
It would do 13.5 sec qtrs all day long and got down to a 13.1 with slicks. You remember Bewy as I raced you plenty of times.
Well that car was a really civilised car on the street , would pull down below 1000 rpm in top gear and just pull away with no fuss and rev to 7500rpm easily.
It had a mopar performance 292/510 cam in it and I loved it!
Thirty years later when I built my 410 I decided to go for the 292/510 cam again.
I hated it as it would buck and jump at low revs and didn,t really smooth out until about 1600 rpm.
Now what was the difference? The old one was on a 114 lobe sep and the new one you could only get in a 106 l/sep.
I now have a custom hyd roller designed by Mike at B3 and is a 242 @ 50 with 610 lift on a 112 l/sep and it revs hard and has done a low even sec qtr @ 120 mph and is a total dream to drive. It does not jump and buck and idles with a noticable lope but performs very smooth and has even got 23mpg on a recent trip.
Not everyone is after the last bit of HP but with a wider l/sep you can have a much better behaved street cruiser!
 
Jim,
A tight LSA cam with less duration can also idle smooth, see post # 309.... & give more power. Since both cost the same, I will take the one that gives the bonus: more power. Cheers.
 
375inStroke said:
You said it was a religion.
Click to expand...
Did not, said it felt like someone trying to get you to join their religion, like those dudes that show up to your door, obviously I was joking. But some of the DV guy's take everything he says as gospel and if I just read his words (which I have) I'll understand the true way.

 
Last edited:
LO23M8B said:
So what is the formula for a Hemi engine?
Click to expand...
There isn't a 1 formula fit's all Hemi builds or any other type of engine. Intended use and all variables involved will determine what cam or even type of cam to be best for combo, Ex you wouldn't get great results in a 318 with 106 cam 238 degree with 3.23 gears, even if the formula says so. or better yet Customers build an engine with healthy components and then go put a .50 6 speed overdrive and tell me the car bucks at 60mph. Really???? reving 1700 with a 246 cam. So the short answer is choose a cam accordingly to everything in your car. Like baking a cake , it's an entire recipe
 
360duster said:
i read a book from DV, got convinced regarding the LSA theory. Had comp grind me a camshaft with 108°LSA instead of the common 110° - bingo, new best ET by quite a bit. All of the tests with somewhat "limited" cylinder heads show gains when reducing the LSA up to a certain point. One day i´ll try a 106°LSA cam (that´s what the formula shows for my next combination).
Click to expand...
I used to run the mopar performance 280 cam. It is a .474 lift with 110° lobe separation. I ran it dot to dot in a warm 360 in my dart sport with 3.55's and it scooted well. Also for intake I had the Edelbrock airgap. Fast-forward to 2022 I decided I wanted to try the 292 mopar cam with 108° lobe separation. So I changed out 280 cam for the 292 cam. This one I installed it @ 4° advanced on the Cloyes timing set. I also went ahead and changed my rear gear to 3.91's. Even further, I said what the heck let's switch from the airgap to the Victor 340 single plane intake. These changes alone gave my dart a wake up call. Not dramatic but enough to make it more fun to drive.
 
IMO, in order for this formula to be "proven", it would have to be found successful on every single type of engine with a camshaft and that's impossible.
 
a-bodyguy said:
best old school cam i ever used g/k ft 243@50 508 lft 108 lsa in 106
took that out put in a hemi grind 484 cam was in about 2 weeks
g/k was much better
Click to expand...
That g/k grind is almost identical to the 292 mopar cam. Sounds like a nice grind.
 
There is a 30 min video that proves the 128 formula works, & proves it more than once. From memory, the video is called 'The Cattle dog garage'.
 
Bewy said:
There is a 30 min video that proves the 128 formula works, & proves it more than once. From memory, the video is called 'The Cattle dog garage'.
Click to expand...
Yes that's the video that started this thread back in Feb, post 1, cause I didn't really find that it proved it to me. Guess depends how you see DV's claims are.
 
Last edited:
You must log in or register to reply here.
-

Back
Top