Does this prove David Vizard's 128 lsa formula ?

[Hysteric]

Any details of the parts and work put into it and it's performance ?

I bought the car with the engine in it as an unfinished project. My machinist screwed the combo together under the advice of a well respected Mopar racer in the US.

Basically a 9 to1 360, heads were 302's with a 1.84 valve no real port work just a tidy up around the valve job, Air gap 750 3310 carb (early list) a 256 @ .050 solid cam and 1 and 5/8 headers.

 

[Ant]

Umm this might be wrong lol

Say you want an 50 degree overlap advertised and 4 degrees @ 0.050" with a 105 lsa, I'm sure you just add half of overlap to lsa and x 2 for duration.

50/2 = 25 + 105 x 2 = 260 advertised and 4/2 = 2 +105 x 2 = 214 @ 0.050"

Edit* just 2 x lsa + overlap = duration guess is easier eg.. 2 x 105 + 50 = 260, 2 x 105 + 4 =214.

And if you want a split cam both have to add up to total duration of both intake and exhaust of a single pattern eg.. 520 (2x260) eg.. so 256/264 on 105 lsa etc..

Pretty sure that's right, maybe someone will verify

This whole cam selection formula thing from DV has sparked my interest, maybe I might try it for the next engine I do. I want get more engine performance books, maybe I might pick up DV's How to Build Horsepower book.

 

[273]

This whole cam selection formula thing from DV has sparked my interest, maybe I might try it for the next engine I do. I want get more engine performance books, maybe I might pick up DV's How to Build Horsepower book.

I really liked his "Performance With Economy" book it's out of print you would have to find it 2nd hand.

 

[Newbomb Turk]

This whole cam selection formula thing from DV has sparked my interest, maybe I might try it for the next engine I do. I want get more engine performance books, maybe I might pick up DV's How to Build Horsepower book.

Save your money for that book. Go to speedtalk.com and see if you can still get a copy of The Horsepower Chain.

Not only will it change the way you think about internal combustion engines and how they really work.

It also has actual math. Not empirically derived crap.

 

[Ant]

Save your money for that book. Go to speedtalk.com and see if you can still get a copy of The Horsepower Chain.

Not only will it change the way you think about internal combustion engines and how they really work.

It also has actual math. Not empirically derived crap.

There is nothing there to buy, not much I can do on the site to find the book. Maybe it's because I'm on mobile? I'll check around on the interweb and see if I can find it. Thank you though.

 

[Newbomb Turk]

This whole cam selection formula thing from DV has sparked my interest, maybe I might try it for the next engine I do. I want get more engine performance books, maybe I might pick up DV's How to Build Horsepower book.

If you have an engine you want a cam spec’d for let me know bore, stroke, rod length, compression ratio and at what RPM you want to make peak torque and I’ll run some numbers.

I can’t tell you exactly what the numbers might be because it sometimes throws out some crazy numbers.

 

[Newbomb Turk]

There is nothing there to buy, not much I can do on the site to find the book. Maybe it's because I'm on mobile? I'll check around on the interweb and see if I can find it. Thank you though.

I’ll check on it for you. I can’t remember exactly what you have to do to get one.

 

[Newbomb Turk]

There is nothing there to buy, not much I can do on the site to find the book. Maybe it's because I'm on mobile? I'll check around on the interweb and see if I can find it. Thank you though.

Ok, if you go back to speedtalk and on the page that lists all the forums you click on the announcements tab.

Right at the top of that page is a button that says “limited supply of Don Terrell’s horsepower chain”.
click on that and the instructions to get one is there.

They are only 40 bucks right now. That’s a smoking deal.

 

[Ant]

I’ll check on it for you. I can’t remember exactly what you have to do to get one.

That's alright. Speed Secrets says they will have it soon.

Edit: I replied late.

 

[Hysteric]

They are only 40 bucks right now. That’s a smoking deal.

That's cheap!

 

[Hysteric]

I'd also look at getting PIPEMAX also.

PipeMax Professional Engine and Header Design

 

[RustyRatRod]

You really need the seat to seat timing numbers and at what checking height was used to get it.

The engine sees seat to seat timing. Not at .050 timing.

Yeah, the .050" thing was introduced just to kinda "level the playing field" and be able to compaer one to another. But when the wheel comes out, it's a different story.

 

[Bewy]

Ant,
Get DVs SB Chevy book, SA books #57. Money well spent.

It has a couple of pages of cams, hyd & solids, FTs & rollers, from mild to wild, for various engine sizes. It gives LSA & duration for these cams & you will be able to make an INFORMED decision on a cam for your engine.

I believe 273 touched on this earlier & I am not sure if it is in this book or his BBC book: if you want more low end or smoother idle, do NOT widen the LSA, reduce the duration.

 

[Bewy]

You really going to rely on 'Adv duration' numbers?
The Chrys cam & the Pontiac cam have 225 & 224 @ 050. Their adv numbers are 284 & 301.......
Or two Crane cams, both 273 @ 050, but 308 & 330 Adv duration.

 

[Newbomb Turk]

You really going to rely on 'Adv duration' numbers?
The Chrys cam & the Pontiac cam have 225 & 224 @ 050. Their adv numbers are 284 & 301.......
Or two Crane cams, both 273 @ 050, but 308 & 330 Adv duration.

View attachment 1716256932

I’d explain to you why you use seat to seat timing but you can’t learn.

And of course if your god Vizard doesn’t say it you don’t know it.

I wouldn’t buy another DV book with a gun to my head.

Have you ever even seen The Horsepower Chain? That one book exposes a lot of garbage put out by lots of people.

 

[Bewy]

Turk,
You couldn't explain anything to anybody because you know nothing....

 

[Ant]

Ant,
Get DVs SB Chevy book, SA books #57. Money well spent.

It has a couple of pages of cams, hyd & solids, FTs & rollers, from mild to wild, for various engine sizes. It gives LSA & duration for these cams & you will be able to make an INFORMED decision on a cam for your engine.

I believe 273 touched on this earlier & I am not sure if it is in this book or his BBC book: if you want more low end or smoother idle, do NOT widen the LSA, reduce the duration.

I plan on purchasing a few books by multiple authors when I get the chance. This will expand my knowledge further and I will have multiple sources to compare and contrast.

As for the cam LSA, DV's 128 formula thing kind of goes against what I have learned in the past. Usually too short LSA is bad for vacuum and very low end power is what I've learned and has been the opinion by many others. Is it right? IDK. Most of my experience is dealing with factory stock stuff, but learning more about high performance stuff is fun.

Edit:
(Those options I heard by the many others past were somewhat incorrect.)

BTW, quote me when you reply to me. This way I get the notification.

 

[273]

As for the cam LSA, DV's 128 formula thing kind of goes against what I have learned in the past. Usually too short LSA is bad for vacuum and very low end power is what I've learned and has been the opinion by many others. Is it right? IDK.

Overlap is what can kills vacuum, which is a combination of lsa and duration, people generally will sacrifice lsa for more duration, DV position is to do the opposite, run the required lsa (builds more low and mid torque) and sacrifice duration instead for acceptable overlap.

Now I haven't seen any dyno test that been designed exclusively to compare this out. We know generally a tighter lsa will gain low/mid torque from the test I've seen about an average of 2-4 lbs-ft per degree of lsa, but that's with the same duration so who knows if gain is the same/better/worse with less duration to keep similar overlap.

 

[Ant]

Overlap is what can kills vacuum, which is a combination of lsa and duration, people generally will sacrifice lsa for more duration, DV position is to do the opposite, run the required lsa (builds more low and mid torque) and sacrifice duration instead for acceptable overlap.

Now I haven't seen any dyno test that been designed exclusively to compare this out. We know generally a tighter lsa will gain low/mid torque from the test I've seen about an average of 2-4 lbs-ft per degree of lsa, but that's with the same duration so who knows if gain is the same/better/worse with less duration to keep similar overlap.

Tests would be cool to see on this. 2-4 lbs-ft per degree of LSA does not seem like alot, but I guess in racing every little bit counts.

 

[273]

Tests would be cool to see on this. 2-4 lbs-ft per degree of LSA does not seem like alot, but I guess in racing every little bit counts.

Well if you go 116 to 108 that's 16-32 lbs-ft but ya go from 110 to 108 not gonna be that huge, 4-8 lbs-ft gain. From what I've noticed on the few lsa comparisons we got, as you go tighter than gains get smaller so going 112 from 116 could get better average gains then going 108 from 112. 110 is probably a decent compromise for a lot of engines why it has became the defacto hot street performance lsa.

 

[Mattax]

What dyno is capable of showing vacuum at idle?
Com'on. Can even any eddy current setup chassis dyno hold steady or do a stepwise down at 1000 never mind 650 rpm?

You want to test a bunch of theoretical changes? There's several decent simulators including pipemax, dynomation, and even more expensive ones. There was a program that used to come (or maybe it was optional) with some of the Speed-talk Horsepower chain packages. Dynomation's F&E model will provide lower rpm (maybe down to 1000 or 1500 rpm) but I wouldn't rely on it being that accurate.

 

[273]

What dyno is capable of showing vacuum at idle?
Com'on. Can even any eddy current setup chassis dyno hold steady or do a stepwise down at 1000 never mind 650 rpm?

You want to test a bunch of theoretical changes? There's several decent simulators including pipemax, dynomation, and even more expensive ones. There was a program that used to come (or maybe it was optional) with some of the Speed-talk Horsepower chain packages. Dynomation's F&E model will provide lower rpm (maybe down to 1000 or 1500 rpm) but I wouldn't rely on it being that accurate.

The dyno test I'd like to see, Eg.. say DV formula says 109 lsa with 65* of overlap, run it against cams from say from 100 to 120 lsa with 65* of overlap, I mainly like to see going tighter lsa.

 

[Bewy]

Ant,

There is a 30 min video by the Cattle Dog Garage. [ Not the 1hr + video ]. Odd name, I know....
He tests the 128 rule with multiple cams....& verifies it works.
What a lot of people do not seem to realise....is that the LSA is telling you where the valves are at max lift. Common sense tells you that max air flow into the cyl is going to be close to, or at max lift. A cam with a 110 LSA installed straight up has the exh valve at max lift 110* BTDC & the int valve is at max lift 110 ATDC. Why is that important? On the intake stroke [ more importantly at low & medium rpms ], the depression [ suction ] of the piston going down the more draws in the air....to make HP on the power stroke. Piston moves quicker, pulls more air all else being equal. When is it quicker? Piston speed is zero at TDC & BDC, but quickest somewhere in between. Where in between? The calculation for mean [ average ] piston speed is a simple one. But the calculation for piston speed at a given crank angle is more complicated & involves sine function.
I suspect there is a correlation between max piston speed & max [ or near max ] valve lift & that evolved into the 128 rule.

 

[RustyRatRod]

What dyno is capable of showing vacuum at idle?
Com'on. Can even any eddy current setup chassis dyno hold steady or do a stepwise down at 1000 never mind 650 rpm?

You want to test a bunch of theoretical changes? There's several decent simulators including pipemax, dynomation, and even more expensive ones. There was a program that used to come (or maybe it was optional) with some of the Speed-talk Horsepower chain packages. Dynomation's F&E model will provide lower rpm (maybe down to 1000 or 1500 rpm) but I wouldn't rely on it being that accurate.

One really good "simulator" called the dragstrip. lol

 

[273]