Does this prove David Vizard's 128 lsa formula ?

[Hysteric]

Larry on his approach:

Now I'll address your head related questions: With the exception of blown applications, ports don't just flow one direction. Intake ports pulsate back and forth, and exhausts flow backwards too. This occors primarily at overlap, when the cylinder still has positive exhaust trying to exit the exhaust port ...where header back pressure is pushing backwards. Now the intake valve (which is larger in diameter) opens, and exhaust gasses seeking the path of least pressure take the easy way.....the intake port "exit". This is not a good thing because besides turning the intake port black "reversion" also contaminates the intake charge with inert gasses which will not burn again. My studies showed a direct correlation between low lift intake flow and reverse flow.....The better the low lift flow on an intake port, the better the tendency for reverse flow, or sucking exhaust. I designed my intake ports to not flow worth a **** at low lift, and also to not flow backwards. I'll not detail how, but the approach to the inlet valve seat, and its blend to the chamber are how it's accomplished....remember the seat is only the 45 degree angle that's ~ .055" wide. were not talking about the seat ring itself. The assymetric shapes I developed for that area and the last .5" of the intake port (the wierd valve job) are why the port doesn't dare flow backward, and as for low lift flow......study the piston velocity when the valve's at .150" or less. You'll find that it's so slow that the port's not being sucked on at all(relatively speaking), so big flow #'s at low lift wouldn't do you any good anyway. If I had known how to design an intake port that flowed 0 cfm. up to .150" lift, I would have, but all things considered my "weird seats" worked well for their time.
Exhaust ports: Read my Re. to RX first. I've never had much luck with performance of engines with no exhaust valves, so I've never been inclined to design exhaust ports without valves included. All I'll say is that the some flow attaches itself to the head and stem on the exhaust side, so the valve is somewhat like a guide for flow. The thing you're missing when flowing with no valve is that the valve stem represents part of the cross sectional area of the port, and, as previously stated areas are critical when dealing with velocities over mach 1. My port phylosophy has always been to calculate how much air a given displacement engine needs to run at a given rpm range (taking into account the many variables such as bore / stroke / rod length, and of course rules), and design a high velocity intake port that's not too large or so small that the velocities will cause separation of a well prepared air / fuel mixture.

Larry Widmer.

 

[Dale Davies]

Well in those dynos buddy uses as evidence they gain the tighter you go, from 120 to 101 at an average of 3 lbs-ft per degree, So if your example followed that trend 108 would make about 6 lbs-ft more than 110 and 106 would of made 6 lbs-ft over 108 and 104 would make another 6 lbs-ft, but the gains as they got tighter the gap did shrink but there was gains.
If those held up to lose 30-50lbs-ft + over recommended 108 you'd have to run 118-125 + lsa.

Like I said doesn't necessary disprove maybe cast a doubt but certainly doesn't prove.
Especially when most use a 116 at worse and more like 108-112 and the formula generally recommends 105-110.

Adjust as per DV recommendations regarding CR and low lift flow.

 

[Dale Davies]

Somewhat repeating myself here, but I've spent my dollars on DV and one has to assess both his strengths and his weaknesses of not just his understanding, but in the time and space available for his explanations. There's a reason one gets much more out of an HP Book than an SA Book. There are other things going on but
lets get back to the topic of picking of cams and the role of LSA.



Rod stroke makes a difference because it changes the time the piston will dwell at the top vs bottom of the stoke. The valve openings and closings ought to work with piston dwell and take advantage of it rahter than fight it.





Those are interesting observations regarding reversion and chosing valve closing and opening points from a guy in the trenches involved with everything from motorhomes and commercial trucks to motorsports. Because a guy who focused on combustion and tuning mostly for racing (but also to meet Aussuie emissions rules) explained that same thing although from a slightly different perspective.

Shrinker wrote:
A wide LSA creates high vaccum at idle for sure but it also does other things. I prefer to think of LSA in the old ways of overlap because at least calling out the overlap amount at TDC defines the actual event rather than you having to calculate it. The overlap of the valves allows the exhaust to supply gases to the intake system depending upon the physics of what is happening in the exhaust at the time. I have done tests that indicate that large cam motors actually run on substantial amounts of air inducted through the exhaust backwards into the intake manifold. Decreasing the overlap reduces this and allows better controll of the mixture. Quite a lot of the time the exhaust system functions as a uncontrolled carburetor, in as far as it has combustible gases in it that are drawn into the engine.
...
How this all relates to idling is that the LSA is the un-throttled connection of the inlet to the exhaust. If the exhaust gas is going gang busters and doing all super scavenging stuff and being nice and not blowing up the intake then you can get high manifold vacuum. High manifold vacuum helps you to turn the fuel into a gas before it gets compressed.
Theres not much gas being compressed inside a cylinder when the engine is idling so you dont get much compression energy. An engine wont run at all unless the fuel is turned into gas and its the amount of gas at ignition time that determines the quality of the burn and the quality of the burn is what causes the exhaust to behave properly or be a pain in the butt.
...
Measuring it as LSA is a modern thing that I think confuses the issues of the overlaps effects. Ed Iskendarian got it right when he said its the fifth cycle [overlap]. And thats the best way to understand it, you have to know the ramps and imagine the effects etc. I fully realise that you can have different durations with the same LSA and therefor you get a different overlap.
I was talking in terms of varying the LSA without changing the duration. We were discussing the idle vacuum verses duration which is of course not the most important influence on the vacuum; its predominantly the overlap that affects idle vacuum. As the overlap is an "unthrottled" inlet to the inlet manifold.
LSA is a useless number in my opinion as you have to calculate what the overlap and bottom fills are but its convenient to use for advertising reasons i suppose and its whatever you get used to.

So this is a deeper explanation of why I think LSA can be useful for comparing cams but the valve events for the specific engine should be the main focus. Also very very important is what the engine needs to do. A circle track cam can focus on a narrow rpm range whereas other applications are going to want a much broader power range.

LSA is a specification of the cam grind. Overlap is a function of LSA and duration.

 

[Newbomb Turk]

Larry on his approach:

Now I'll address your head related questions: With the exception of blown applications, ports don't just flow one direction. Intake ports pulsate back and forth, and exhausts flow backwards too. This occors primarily at overlap, when the cylinder still has positive exhaust trying to exit the exhaust port ...where header back pressure is pushing backwards. Now the intake valve (which is larger in diameter) opens, and exhaust gasses seeking the path of least pressure take the easy way.....the intake port "exit". This is not a good thing because besides turning the intake port black "reversion" also contaminates the intake charge with inert gasses which will not burn again. My studies showed a direct correlation between low lift intake flow and reverse flow.....The better the low lift flow on an intake port, the better the tendency for reverse flow, or sucking exhaust. I designed my intake ports to not flow worth a **** at low lift, and also to not flow backwards. I'll not detail how, but the approach to the inlet valve seat, and its blend to the chamber are how it's accomplished....remember the seat is only the 45 degree angle that's ~ .055" wide. were not talking about the seat ring itself. The assymetric shapes I developed for that area and the last .5" of the intake port (the wierd valve job) are why the port doesn't dare flow backward, and as for low lift flow......study the piston velocity when the valve's at .150" or less. You'll find that it's so slow that the port's not being sucked on at all(relatively speaking), so big flow #'s at low lift wouldn't do you any good anyway. If I had known how to design an intake port that flowed 0 cfm. up to .150" lift, I would have, but all things considered my "weird seats" worked well for their time.
Exhaust ports: Read my Re. to RX first. I've never had much luck with performance of engines with no exhaust valves, so I've never been inclined to design exhaust ports without valves included. All I'll say is that the some flow attaches itself to the head and stem on the exhaust side, so the valve is somewhat like a guide for flow. The thing you're missing when flowing with no valve is that the valve stem represents part of the cross sectional area of the port, and, as previously stated areas are critical when dealing with velocities over mach 1. My port phylosophy has always been to calculate how much air a given displacement engine needs to run at a given rpm range (taking into account the many variables such as bore / stroke / rod length, and of course rules), and design a high velocity intake port that's not too large or so small that the velocities will cause separation of a well prepared air / fuel mixture.

Larry Widmer.

That quote needs to be a sticky.

 

[273]

Adjust as per DV recommendations regarding CR and low lift flow.

If your general argument is that going with DV's recommendations over the generally wider lsa people run will gain you some mid range torque then I agree with you, just not seeing evidence for 40-50 lbs-ft.

But this thread is about video at the begin of it, fast forward to his dyno proof, do you find it proof or not? I don't, all I am saying, really not suppose to be a debate about DV.

Watch the video and let me know or not, but stop using DV words as proof, show dyno results.

 

[Bewy]

NBT,
So you need extra exh duration to make HP? The turbo guys didn't get the message....nor Jon Kaase who won the EMC contest with a 400 Ford engine that made 660 hp. It used a FT cam that had 246/238 @ 050 duration....on a 98 LSA & 92 ICL. Hmm....

 

[Bewy]

Richard Holdener did a two cam test about a month ago on a 5.3 LS engine. Maybe somebody can link it?
Cam 1: over 600 lift, 234/248 @ 050 113.5 LSA
Cam 2: 550 lift, 218/230 @ 050, 105 LSA

Cam 2 made 60 ft lbs more on the low end & crossed over at about 5000 rpm with cam 1. So below 5000 it was stronger.
Cam 1 made more peak hp, but it had 16* more duration & lift....Hmm.

 

[Newbomb Turk]

NBT,
So you need extra exh duration to make HP? The turbo guys didn't get the message....nor Jon Kaase who won the EMC contest with a 400 Ford engine that made 660 hp. It used a FT cam that had 246/238 @ 050 duration....on a 98 LSA & 92 ICL. Hmm....

It depends. So yeah, single pattern cams have their place but its usually over valved on the exhaust side. Take a look at a 632 Chevy. Most of the cams for those have a 15-20 degree split, maybe more. The current trend is huge strokes and small exhaust valves to get the biggest intake valve you can. So it takes more time/area to use blowdown to it's most effective value.

Its not 1985 any more so don't build an engine like it is.

I couldn't care less what the hair dryer crowd does.

 

[273]

Here's DV own dyno proof, (finish later got to go)

 

[273]

Even in DV's own dyno proof doesn't show the 40-50 lbs-ft gain 1.4 lbs-ft per cid torque level etc..

Does it show what we already knew? That going tighter gains mid range torque, from the dyno graphs I've seen so far about an average of 3 lbs-ft per degree, starts off a little higher and gets less as it gets tighter.

In this one seems about 6 lbs-ft per degree from 111-108 a little higher then other few similar test have shown and the gains seemed to shrunk 1 lbs -ft per degree after 108, and this one unlike the others had a decently different peak hp.

Is 108 optimal in this one, 105 barely gain I guess most would say ain't worth it but 18-20 lbs-ft between 111 & 108 people looking for driveability would probably stayed with 111 but anyone wanting good overall power would take the 108.

This is one he choose out of 1000's of runs to verify his position, if this is the trend looks like it gets you into the ballpark.

 

[George Jets]

318 Dyno Pull



Here is a close to stock (sort of) 318 Magnum with a fresh top end and something like a 340 cam grind.

.274 on 114 lobe centers.

253 Wheel Horse Power

Add 75 HP for driveline loss.

253 + 75 =
"328 HP" at crankshaft

They are running 600 cfm Edelbrock.

Pretty darn good for a sort of stock 318 Magnum with a fresh top end.

Running a 114 cam, at 4765 rpm.


☆☆☆☆☆

 

[Hysteric]

Now put some comp into that 318....

Here's the cam regrind @ Crower:

 

[273]

318 Dyno Pull



Here is a close to stock (sort of) 318 Magnum with a fresh top end and something like a 340 cam grind.

.274 on 114 lobe centers.

View attachment 1716216156

253 Wheel Horse Power

Add 75 HP for driveline loss.

253 + 75 =
"328 HP" at crankshaft

They are running 600 cfm Edelbrock.

View attachment 1716216157

Pretty darn good for a sort of stock 318 Magnum with a fresh top end.

Running a 114 cam, at 4765 rpm.


☆☆☆☆☆

With more lift and exhaust duration Richard Holdener got 350 hp out of a 5.9l magnum.

 

[George Jets]

With more lift and exhaust duration Richard Holdener got 350 hp out of a 5.9l magnum.

The above video is about him maximizing his 318 at a minimal cost, and utilizing his original valve train to work with the new cam grind numbers.

Not "You Should Drop in a 360".

318 ^^^

☆☆☆☆☆

 

[Newbomb Turk]

318 Dyno Pull



Here is a close to stock (sort of) 318 Magnum with a fresh top end and something like a 340 cam grind.

.274 on 114 lobe centers.

View attachment 1716216156

253 Wheel Horse Power

Add 75 HP for driveline loss.

253 + 75 =
"328 HP" at crankshaft

They are running 600 cfm Edelbrock.

View attachment 1716216157

Pretty darn good for a sort of stock 318 Magnum with a fresh top end.

Running a 114 cam, at 4765 rpm.


☆☆☆☆☆

How did you come up with a 75 HP loss?

 

[273]

The above video is about him maximizing his 318 at a minimal cost, and utilizing his original valve train to work with the new cam grind numbers.

Not "You Should Drop in a 360".

View attachment 1716216182

318 ^^^

☆☆☆☆☆

You missed my point, your saying your figuring around 328 at crank, I'm saying the 5.9l with a bit more cam got 350 hp to me that's pretty close to each other.

 

[George Jets]

How did you come up with a 75 HP loss?

20%
Read the comments in the above video, the Sorta Stock owner of the 318 Magnum talks about it, along what the cam grind numbers Crowler helped him select.

Thank You...

☆☆☆☆☆

 

[George Jets]

1 Horse Power per cu.in.
Not all bad ^^^ on a minimal budget. Sorta Stock 318.

☆☆☆☆☆

 

[Dale Davies]

Conversion from gross HP on an engine dyno, net HP on an engine dyno with all accessories and exhaust as installed in the vehicle and wheel HP as determined on a chassis dyno. Friction in the drivetrain and tires on the dyno rollers drop the seen reading. More or less a standard, but some drivetrains will show more or less reduction. An example is the Ford 9" as compared to the 8.8" differentials. It is accepted the 9" is stronger but has more frictional loss.
Then there is net power. When the General came out with the rounded Caprice body style that sold well to police forces, they came with the LT1 Optispark engine. In a Corvette it was 300 HP. In a Camaro it was rated at 275HP. In the Caprice the rating dropped to 250HP. Pretty much most of the difference was in the exhaust system. Corvette owners would be more tollerant of more exhaust noise. The General did work to keep the sound level down. Camaro owners take in a more broad spectrum with more wannting a fairly quiet exhaust. Then you get to Caprice purchasers that are looking for Cadillac quiet.
When you use a hub dyno tire friction is taken out as a factor.
Maybe 20% compensation is a bit high, and 15% may be closer. Without pulling the engine and running it on a dyno we can not know the exact drivetrain loses.

 

[Newbomb Turk]

20%
Read the comments in the above video, the Sorta Stock owner of the 318 Magnum talks about it, along what the cam grind numbers Crowler helped him select.

Thank You...

☆☆☆☆☆

You didn't say 20% in your comments and I'm not interested in the video. Depending on what it is 20% is probably 2 or 3 percent low so now I'll ask how did they come up with 20%.

And remember I do not want to watch the whole video, which is why I asked in the first place.

 

[Newbomb Turk]

Conversion from gross HP on an engine dyno, net HP on an engine dyno with all accessories and exhaust as installed in the vehicle and wheel HP as determined on a chassis dyno. Friction in the drivetrain and tires on the dyno rollers drop the seen reading. More or less a standard, but some drivetrains will show more or less reduction. An example is the Ford 9" as compared to the 8.8" differentials. It is accepted the 9" is stronger but has more frictional loss.
Then there is net power. When the General came out with the rounded Caprice body style that sold well to police forces, they came with the LT1 Optispark engine. In a Corvette it was 300 HP. In a Camaro it was rated at 275HP. In the Caprice the rating dropped to 250HP. Pretty much most of the difference was in the exhaust system. Corvette owners would be more tollerant of more exhaust noise. The General did work to keep the sound level down. Camaro owners take in a more broad spectrum with more wannting a fairly quiet exhaust. Then you get to Caprice purchasers that are looking for Cadillac quiet.
When you use a hub dyno tire friction is taken out as a factor.
Maybe 20% compensation is a bit high, and 15% may be closer. Without pulling the engine and running it on a dyno we can not know the exact drivetrain loses.

It's probably low at 20. Thats why I asked where the number came from. I have never EVER seen a 15% loss on a wheel dyno. You can drop the tires pressure a couple of pounds and lose 2 or 3 percent. Where the tires are on the rollers change that percentage.

The only way to know what the friction losses are is to do a coast down.

Some shops are so lazy they won't do it. And some people wonder why their dyno numbers are off.

Come to think of it, didn't @boosted have his car on a chassis dyno? And if IIRC his car ran pretty much what the dyno said it would. That says to me his dyno operator has his **** in one group.

 

[273]

In the Richard Holdener video did his van on a chassis dyno and engine dyno, the chassis dyno made 68-72% of what it did on the stand.

 

[Bodyperson]

Conversion from gross HP on an engine dyno, net HP on an engine dyno with all accessories and exhaust as installed in the vehicle and wheel HP as determined on a chassis dyno. Friction in the drivetrain and tires on the dyno rollers drop the seen reading. More or less a standard, but some drivetrains will show more or less reduction. An example is the Ford 9" as compared to the 8.8" differentials. It is accepted the 9" is stronger but has more frictional loss.
Then there is net power. When the General came out with the rounded Caprice body style that sold well to police forces, they came with the LT1 Optispark engine. In a Corvette it was 300 HP. In a Camaro it was rated at 275HP. In the Caprice the rating dropped to 250HP. Pretty much most of the difference was in the exhaust system. Corvette owners would be more tollerant of more exhaust noise. The General did work to keep the sound level down. Camaro owners take in a more broad spectrum with more wannting a fairly quiet exhaust. Then you get to Caprice purchasers that are looking for Cadillac quiet.
When you use a hub dyno tire friction is taken out as a factor.
Maybe 20% compensation is a bit high, and 15% may be closer. Without pulling the engine and running it on a dyno we can not know the exact drivetrain loses.

The difference for the caprice was compression ratio too. I can’t believe this isn’t a bigger part of this discussion. All of this discussion also seems like all out racing applications. It’s not. Sure, run the tight separation but dialing back your timing to run on pump gas is a power killer or don’t and kill power with detonation.

 

[Dale Davies]

The difference for the caprice was compression ratio too. I can’t believe this isn’t a bigger part of this discussion. All of this discussion also seems like all out racing applications. It’s not. Sure, run the tight separation but dialing back your timing to run on pump gas is a power killer or don’t and kill power with detonation.

I did state probably most of the power difference was exhaust system related. But you are correct in that the Caprice had slightly lower compression.

 

[Bodyperson]

I did state probably most of the power difference was exhaust system related. But you are correct in that the Caprice had slightly lower compression.

Iron heads too comparatively speaking but getting caught up wrong in the discussion at hand.