High velocity header collectors, are they worth it?

[Greg Hill]

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.

[Ed Wright]

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?

[Chris Hill]

Originally Posted by Ed Wright

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?

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.

[Ed Wright]

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.

[Dave Ribeiro]

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

[gmonde]

Originally Posted by Dave Ribeiro

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

[SSDiv6]

Because there is an array of differences between engine designs and components used, especially camshaft designs, establishing the correct header size for any engine can be complicated and many times considered a mystery.

As others have said, headers that work in the dyno may not work at the track. For many years, the old belief was the larger the header, the more power the engine will make. (The old “Bigger the Better” Theory) The reality is many are running engines with headers that are too big in size for its application.

I have examined data from both dyno and track date were a Comp Eliminator engine gained a lot of power by switching from a 2-Step header to a 3-step design with smaller primaries and merged collectors. Very interesting to see how the change affected both the BSFC and EGT also eliminating a reversion issue that the engine was experiencing.

In the early days and prior to the advent of computers when we had to use a slide rule, paper and pencil, I recommended the use the guide lines as shown in the book titled; “Scientific Design of Exhaust & Intake Systems (Engineering and Performance) by Philip H. Smith and John C. Morrison. Another good book is Practical Gas Flow by John Dalton.

To have an idea on what it takes to design the proper header for your car, the elements and factors to be considered, just go to the Burns Stainless or Kromer Kraft Headers website and look at the “Race/Engine Specification Forms” and you will have an understanding of all the parameters they take in consideration when designing a header.

In fact, Calvin Elston asks potential customers to fill the form from Burns Stainless and when they get the results, he will discuss the recommendations and add his input based on his prior experiences.

Mark at Performance Welding Headers has a lot of knowledge and experience he gained throughout the years while working at Ak Miller Turbo. Ak Miller was the pioneer of race and street turbocharging and much of today’s turbo technology started at Ak’s shop. Much of the power of turbocharged engines is dependent on proper exhaust design. I believe this is one of the many reasons why his headers work so well and because he has taken the time to read and study many of the published SAE treatises and publications on exhaust science.

This is not taking away from other great header builders such as Stahl and Gebbler.

If you are serious about the performance of your car and have the budget, stay away from other brands that just bend tubes to build headers to fit a specific chassis and do not take in consideration how the will perform.