Bill Jenkins , Larry Meaux and header wisdom.

[joespanova]

I always found it interesting how PipeMax predictions never coincided with Jenkins regarding primary size , length and collector. Now here's a guy ( Jenkins ) who did nothing BUT flog everything on the track and dyno in probably every conceivable combination...going so far as to dictate the primaries should be 2.125 as large as 2.250 with lengths and esp. collectors ( Jenkins suggestion a 4 inch collector ) that given an engine speed of 9500 RPM in a 331 inch engine with heads that back then probably move around 320ish....maybe a little more. At those speeds and power levels PipeMax predicts what most engine guys and header guys know , today. That the header would be somewhere around 1.890-2.05 ish.and the collector would either be a merge ( some variation of ) or even a straight at 3.5 inches. It doesn't matter that it was a long time ago....Jenkins was into discovery and smaller should have worked back then.....
Why didn't it?

[hoffman900]

As smart as Bill Jenkins is, he was only one guy.

No single person, no matter how smart, can test all combinations, especially in the old school matter in which he did. Furthermore, bias’ creep in, maybe things he learned twenty years prior still guided his decisions, and in doing so, clouded his ability to step outside that box.

Lastly, Bill wasn’t unbeatable. He was a top contender in his discipline, but his discipline was very narrow in the motorsports world as a whole.

I mean this in the nicest way as well. He kicked butt in his respective corner of the world of motorsports, and used the tools the period gave him, but he didn’t have unlimited resources and time, and one person can only do so much.

The lone genius in the garage has been romanticized, but it’s not the best way to do things. It worked in a simpler time, but even someone like Colin Chapman would be out of his league in motorsports today.

[joespanova]

Right , thinking "outside the box" .....but given his "innovative" nature , you'd think as many cam shafts , port configurations , manifold creativity , and so on.......header testing is the proverbial "low hanging fruit"

[hoffman900]

Right , thinking "outside the box" .....but given his "innovative" nature , you'd think as many cam shafts , port configurations , manifold creativity , and so on.......header testing is the proverbial "low hanging fruit"

The problem is that an engine is a complex system. So in order to realize gains due to one change, it might require changing 4 other things, and all not obvious.

This is where modern computer engine development is a huge help. I can run through 20,000 possible combinations of primary/secondary/ collector lengths and diameters, intake lengths, and camshaft event combinations before I even assemble a test piece. You still need to dyno test, but you have a HUGE jump on the development.

[joespanova]

Right , thinking "outside the box" .....but given his "innovative" nature , you'd think as many cam shafts , port configurations , manifold creativity , and so on.......header testing is the proverbial "low hanging fruit"

The problem is that an engine is a complex system. So in order to realize gains due to one change, it might require changing 4 other things, and all not obvious.

This is where modern computer engine development is a huge help. I can run through 20,000 possible combinations of primary/secondary/ collector lengths and diameters, intake lengths, and camshaft event combinations before I even assemble a test piece. You still need to dyno test, but you have a HUGE jump on the development.

No doubt , but had he been around today , if he was close by , I'd certainly ask " Bill , did you ever even TRY a smaller pipe set???"

[Old School]

Could some of the differences stem from Jenkins working in a very narrow rpm range where Pipemax works over a much larger range?

In other words, would the header be the same for a 331 in a powerglide super stock car compared to a 331 in a 4/5 speed stick that leaves at 7500, shifts at 9500, never drops below 8300 at any time other than the launch?

[JoePorting]

Those old SBC heads in the 1970's only flowed about 250 CFM intake, exhaust was probably around 210.

[Mummert]

Overly large headers can weaken the scavenge signal. If he was running camshafts with excessive overlap it could have helped him from running into an over scavenging problem. Many people assume that what they see going on with exhaust systems has to do with the blow down phase. More often than not, it has do due with the overlap period.
All builders have their own particular DNA, no matter how much they learn there are certain things that are all them. It could be as simple as, it was what worked with a particular exh. valve tulip angle he liked combined with the overlap in the cam in a narrow power band.

Pipe Max has proven itself many times over on a large variety of engines. I'm sure what Grumpy did worked for him.

[induction apprentice]

I like the topic. It will no doubt open some new and interesting points of view. I would agree Joeporting and mummert are on the right train of thought.

My two cents. Is things are very different now. Very few today would port a stock iron head today with 45 deg seat angles, use medium ratio rockerarms, huge dome pistons and a oem plug location etc. Then go try rev it up to hell and so on. The headers they built back then were they stainless steel or thermal coated. I have no doubt Jenkens tried all different sized header combos. I would bet if we tried duplicate one of his race engines today. We would probably find his header combo works best. That does not suggest to me at all Larrys software is wrong. I suspect it is very good if the right information is put into it.

[Stan Weiss]

This is the Intake from my GK roller from around that time. My understanding is Grumpy's was a very steps wilder.

Stan

Code: Select all

_______I__N__T__A__K__E
Rocker_Arm_Ratio_=_1.500_________Valve_Lash_=_0.02400

VALVE_____Lift______Opens___Closes__Duration
_________________Deg_BTDC__Deg_ABDC_____________Area
_________0.00000____55.73_|_102.97_|_338.71_|__58.34
_________0.00600____51.32_|__97.70_|_329.01_|__58.36
_________0.01000____48.55_|__94.42_|_322.97_|__58.19
_________0.02000____42.63_|__88.27_|_310.90_|__58.15
_________0.04000____33.51_|__78.89_|_292.40_|__57.72
_________0.05000____30.00_|__74.80_|_284.80_|__57.23
_________0.10000____15.35_|__60.60_|_255.95_|__56.26
_________0.15000_____4.49_|__49.63_|_234.12_|__54.23
_________0.20000____-5.08_|__40.21_|_215.13_|__52.08
_________0.25000___-13.74_|__31.55_|_197.81_|__50.48
_________0.30000___-22.16_|__23.29_|_181.13_|__47.43
_________0.35000___-30.55_|__15.09_|_164.54_|__46.00
_________0.40000___-39.21_|___6.57_|_147.36_|__42.07
_________0.45000___-48.48_|__-2.43_|_129.09_|__37.59
_________0.50000___-58.85_|_-12.27_|_108.88_|__32.61
_________0.55000___-71.29_|_-23.72_|__84.99_|__27.20
_________0.60000___-90.19_|_-40.71_|__49.10_|__15.47
CAM
_________0.00600____75.00_|_125.75_|_380.75_|__41.94
_________0.01000____65.60_|_114.12_|_359.72_|__41.78
_________0.02000____51.32_|__97.70_|_329.01_|__41.54
_________0.04000____34.91_|__80.56_|_295.47_|__40.80
_________0.05000____29.65_|__74.50_|_284.14_|__40.39
_________0.10000_____9.63_|__54.44_|_244.07_|__38.49
_________0.15000____-5.25_|__40.03_|_214.78_|__36.40
_________0.20000___-18.14_|__27.24_|_189.11_|__34.41
_________0.25000___-30.72_|__14.92_|_164.21_|__30.48
_________0.30000___-43.87_|___1.94_|_138.07_|__27.53
_________0.35000___-59.07_|_-12.48_|_108.45_|__22.62
_________0.40000___-79.67_|_-31.43_|__68.91_|__14.87

[SpeierRacingHeads]

This would be a lot like what Grumpy worked on. A modern Super Stock 64cc exhaust port.

I think a picture is worth 1000 words.

[nitro2]

Making an exhaust work well at overlap over a narrow rpm range is easy as pie, so that's not where the discrepancy lies.

NA engines making a LOT of power per cubic inch run into blowdown issues, especially so if the heads didn't flow as well as they do today. When you get to that point, the point of having blowdown issues that can't be further effectively addressed with cam and porting, but only by the exhaust, that's when the exhaust has to change drastically. Most people never actually make the drastic changes because ingrained logic and sim soft programs don't point them in that direction.

[hoffman900]

Making an exhaust work well at overlap over a narrow rpm range is easy as pie, so that's not where the discrepancy lies.

NA engines making a LOT of power per cubic inch run into blowdown issues, especially so if the heads didn't flow as well as they do today. When you get to that point, the point of having blowdown issues that can't be further effectively addressed with cam and porting, but only by the exhaust, that's when the exhaust has to change drastically. Most people never actually make the drastic changes because ingrained logic and sim soft programs don't point them in that direction.

Is there an example you can give?

I think of a NASCAR application (I know what works there only applies there), with all their modeling / dyno testing / and validation work (pressure sensors, etc.), and the exhaust systems that Calvin helped introduce to that world in 1993-1994 look relatively the same, minus a tapered secondary.

I believe Grumpy was a fan of header plates. A friend of who built race winning IMSA / SCCA engines, knew people from Grumpy's shop (Philly area) and was also friendly with Jere Stahl. His Toyota engines in the mid-late 1970s were making 122hp/L (pushrod, 2TC engines). Looking back they had large primaries for what it was, and they were running header plates. The idea was the flange / header plate was the AR piece, but it was an idea that came out of conversations with the aforementioned. Granted, that was 45 years ago now, I am not sure what his Pro Stock Truck engines looked like, which I think was the the last time he was developing competitive pro stuff.

[nitro2]

Making an exhaust work well at overlap over a narrow rpm range is easy as pie, so that's not where the discrepancy lies.

NA engines making a LOT of power per cubic inch run into blowdown issues, especially so if the heads didn't flow as well as they do today. When you get to that point, the point of having blowdown issues that can't be further effectively addressed with cam and porting, but only by the exhaust, that's when the exhaust has to change drastically. Most people never actually make the drastic changes because ingrained logic and sim soft programs don't point them in that direction.

Is there an example you can give?

I think of a NASCAR application (I know what works there only applies there), with all their modeling / dyno testing / and validation work (pressure sensors, etc.), and the exhaust systems that Calvin helped introduce to that world in 1993-1994 look relatively the same, minus a tapered secondary.

I believe Grumpy was a fan of header plates. A friend of who built race winning IMSA / SCCA engines, knew people from Grumpy's shop (Philly area) and was also friendly with Jere Stahl. His Toyota engines in the mid-late 1970s were making 122hp/L (pushrod, 2TC engines). Looking back they had large primaries for what it was, and they were running header plates. The idea was the flange / header plate was the AR piece, but it was an idea that came out of conversations with the aforementioned. Granted, that was 45 years ago now, I am not sure what his Pro Stock Truck engines looked like, which I think was the the last time he was developing competitive pro stuff.

Fast blowdown, IF one is at the point where blowdown has become a limiting factor, is not going to be accomplished using small primaries and conventional header dimensions.

Just to be clear, none of my technical input on ST is ever about NASCAR.

[hoffman900]

Making an exhaust work well at overlap over a narrow rpm range is easy as pie, so that's not where the discrepancy lies.

NA engines making a LOT of power per cubic inch run into blowdown issues, especially so if the heads didn't flow as well as they do today. When you get to that point, the point of having blowdown issues that can't be further effectively addressed with cam and porting, but only by the exhaust, that's when the exhaust has to change drastically. Most people never actually make the drastic changes because ingrained logic and sim soft programs don't point them in that direction.

Is there an example you can give?

I think of a NASCAR application (I know what works there only applies there), with all their modeling / dyno testing / and validation work (pressure sensors, etc.), and the exhaust systems that Calvin helped introduce to that world in 1993-1994 look relatively the same, minus a tapered secondary.

I believe Grumpy was a fan of header plates. A friend of who built race winning IMSA / SCCA engines, knew people from Grumpy's shop (Philly area) and was also friendly with Jere Stahl. His Toyota engines in the mid-late 1970s were making 122hp/L (pushrod, 2TC engines). Looking back they had large primaries for what it was, and they were running header plates. The idea was the flange / header plate was the AR piece, but it was an idea that came out of conversations with the aforementioned. Granted, that was 45 years ago now, I am not sure what his Pro Stock Truck engines looked like, which I think was the the last time he was developing competitive pro stuff.

Fast blowdown, IF one is at the point where blowdown has become a limiting factor, is not going to be accomplished using small primaries and conventional header dimensions.

Just to be clear, none of my technical input on ST is ever about NASCAR.

I realize that. I think back to the stub exhaust thread.

My only looking at NASCAR is because the amount of dollars and engineering that has been put into those applications, and even as specialized as they are, the architecture and use is still closer to that than say Formula 1.