CLASS RACER FORUM - High velocity header collectors, are they worth it?

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Re: High velocity header collectors, are they worth it?

Quote:

Originally Posted by JRyan (Post 201326)

Years ago, in the '80's, Jere Stahl used to send out a monthly newsletter to customers with alot of good technical information. Much of it was related to his recent Dyno Testing with headers of all types. We have to remember that Jere was the originator of the Stahl "total tuned headers" and was considered to be the guru of that time with regard to headers.

I remember in one of the tech articles that he mentioned making over 2200 dyno pulls with various engine/header combinations. So he had it all figured out, and all his previous success was well-founded -- right? Not in his words! This isn't an exact quote I'm sure, but it's pretty close; "After 2200 dyno pulls, I found out that neither I nor anyone else knows a damned thing about headers".

Now with computer technology and simulations, people can get better predictions for the correct header, but I know of $3,500 headers, done with computer models, that are hanging on the garage wall, and the old Hooker Supercomp headers with homemade primary extensions and collectors are on the car and FASTER. Now it may be that you'd luck into a problem/solution like Jeff Lee did that would make the $3,500 headers faster, but if the luck didn't occur, you might go through alot of A-B-A testing and without multiple changes (which is usually a no-no), you would never find the sweet spot. I think that was Jere's suggestion. Tune around what you have, and it won't be that far off.

Need proof? How many of you have changed cams, intakes, head flow, converters, or whatever, and have picked up a bunch of ET and never touched the header? Was it right for ALL of those possible combinations? Probably not, and who knows why! Some people have actually gained hugh amounts of HP on the dyno with headers, and SLOWED DOWN on the track. So I guess that you, your car, and the ET slips are the experts on what header is best. Got a ton of money? Try all the headers you want. If you don't, tune around what you have.

Jerry

Good post Jerry.This would be about my luck.LOL

Re: High velocity header collectors, are they worth it?

For those interested, Jere still has all of those news letters, they're available for free on his web site. Jere is still extremely active, and one of the sharpest people I know, and not just about headers, but cam design, data acquisition, dyno operation, and racing in general. He's a lot like Bill Jenkins and Warren Johnson, he's a contrary old codger, but if you can talk sense and knowledge to him, there's a ton of information he has to offer. But he is completely intolerant of B.S. or people that waste his time.

Re: High velocity header collectors, are they worth it?

I have read that equal length primaries (assuming proper diameter) will deliver the most power but in a narrow RPM band, Running different length primaries will lower the peak HP but broaden the HP curve delivering higher average HP over a larger RPM band.

It seems to me that higher average HP should be the goal for a drag motor.

Re: High velocity header collectors, are they worth it?

If the primary length varies enough that some primaries are off enough to lower the amount of HP produced by those cylinders, they'll just lower the overall average HP, in the vast majority of cases.

The reason is that you have an approximately 3" "window" for tuned length. After that, the length of the primary is far enough from the correct harmonic length that it hurts HP over the entire range. That happens because you lose way more off the peak than you ever gain everywhere else.

The "tuned" in the term tuned equal length header refers to the length of the primaries and the collector being tuned to one of the natural harmonics created by the rest of the combination, cam timing, port size, bore, stroke, rod length, etc. If the primary and the collector do not match one of those harmonic lengths, you are not operating in a "tuned" state, and therefor the header is not working with the engine, it is working against it, by disrupting those harmonic tuning lengths. That's a crude layman's way of explaining it, used here for the sake of brevity and clarity.

Obviously, given the constraints imposed by the stock engine location, mostly stock chassis, and ground clearance on a Stock or Super Stock car, it is next to impossible to build absolutely perfectly tuned headers. In some cases, it can be impossible to even get within the 3" "window", at least on the primary tubes, no matter what you do. Also, in some cases, even if you add extra bends to move a tube to get close to the window, between the extra bends and the inch or two that end up from perfect, you're better off to just use fewer and/or less severe bends and live with the incorrect length.

Re: High velocity header collectors, are they worth it?

There are a couple of things I have observed over the years about headers on my car that may or may not be true for others. #1 Is that a dyno is not the place to test headers. Mike Keown told me years ago a bigger header will make more power on the dyno but won't go down the race track like it shows on the dyno and that has been my experience. #2 is what I heard from a really good header builder and that was that the first 8 inches of the primary tubes were the most important part of a header and the size of the first step should match the port size. These are just my experiences on my car and probably aren't relevant for every one else.

Re: High velocity header collectors, are they worth it?

I experienced what Greg mentioned about big headers on the dyno. I quit drag racing in 1980 and went dirt track racing. I had a 358" methanol burning, Hilborn injected engine on Carroll Caudle's dyno, and tried a set of his 2" dyno headers just for grins. My thinking was if my 292" C/SM Camaro liked 2" headers (It did. Thanks Garly), so this 358" should. On the dyno it did, it was up everywhere, as much as 40 ft lbs. Bought a set for the car. It was just plain lazy. My driver said it felt like he was towing something. Finally listened to him and put the smaller ones back on it and it stepped right back up.

Guess we don't race dynos, right? :D

Re: High velocity header collectors, are they worth it?

Quote:

Originally Posted by Ed Wright (Post 201493)

I think allot of that is PROBALLY due to the acceleration rate of the engine being different on the dyno vs. the track. If I remember correctly, on our truck engine design of a 440, the engine will accelerate at 2,000 rpm/second in first gear after the converter locks up. I don't think a dyno can simulate that very well.

What does a superflow test at, 300 rpm/sec correct? I think that is still slower than the accel rate in high gear, but it's been a long time since I've looked at that.

Re: High velocity header collectors, are they worth it?

Chris, that acceleration rate is selectable. Too many years ago, so I don't remember what Carroll was using that day. Most guys use what is closest to their car pulls in high gear. With that dirt car, I have no idea what that would be. No data logger. We had no minimum weight, so if you tossed it up and it came back down, if we could get by without it we didn't use it. :D

Re: High velocity header collectors, are they worth it?

Has anyone done any testing with extentions on merge collectors, also adding to primary tubes ? thanks, in advance.........

Re: High velocity header collectors, are they worth it?

Quote:

Originally Posted by Dave Ribeiro (Post 202146)

Has anyone done any testing with extentions on merge collectors, also adding to primary tubes ? thanks, in advance.........

had a set of hookers 1 7/8 primarys with 3 1/2 collectors ,,added extensions and picked up 2-3 hundreths ,,then i built a set of steps with a smaller collector size,merg collector and picked up about 3 hundreths ,,now this is track results and over many runs and conditions this was the average gmonde