header tube sizing?

I didn't have time last winter to experiment with Mr. Evans exhaust plates and larger BBC Dyno Headers we have at the shop to see what type of HP/Torque gains might have been picked up. Any of you run before and after tests on your combos? I currently run a Hooker Super Comp header with a 2'' Primary and 3.5'' collector in a Fox Body. I know there are some 2 1/8'' to 4'' Fox Body out there. I had to modify the current headers around the steering linkage between using the TFS heads and the K-member spacers to drop engine down in car.

never got a chance to do back to back testing with the different headers , but i now run the kooks 2 1/8 deals and the fittment was great

bruno wrote:never got a chance to do back to back testing with the different headers , but i now run the kooks 2 1/8 deals and the fittment was great

has your engine been moved back any ?

10SHOTS wrote:

bruno wrote:never got a chance to do back to back testing with the different headers , but i now run the kooks 2 1/8 deals and the fittment was great

has your engine been moved back any ?

no , the engine was on solid motor mounts at first and then i just added the front and rear plate

From a set of long tube over 32 inches 2.00 dia 3.5 collector to a set of 28 inch 2.250 stepped to 2.375 and a 4 inch collector on a 900 hp 15:1 557 Box stock P-51's it was worth 50 hp.

But you have the length, diameter, shape and quality of the bends at play here also.

Thanks for the input. My brother has larger tube headers, but Now lives in Florida and I'm in Maryland. I don't think the engine will get pulled out this winter for any testing. I normally run 10.00 index events, but there might be some 6.00 Index 1/8 mile stuff going on this year, and I would need to find a tenth to be competitive without spending alot of money.

Matt Jewell wrote:I didn't have time last winter to experiment with Mr. Evans exhaust plates and larger BBC Dyno Headers we have at the shop to see what type of HP/Torque gains might have been picked up. Any of you run before and after tests on your combos? I currently run a Hooker Super Comp header with a 2'' Primary and 3.5'' collector in a Fox Body. I know there are some 2 1/8'' to 4'' Fox Body out there. I had to modify the current headers around the steering linkage between using the TFS heads and the K-member spacers to drop engine down in car.

Are your headers too low with the K member spacers? I have the spacers and D-D shorty headers, but I have a set of the Hookers hanging on the wall. I have been thinking about trying them, but worried they would be too low. Sorry for the hijack.

IDT-572 wrote:From a set of long tube over 32 inches 2.00 dia 3.5 collector to a set of 28 inch 2.250 stepped to 2.375 and a 4 inch collector on a 900 hp 15:1 557 Box stock P-51's it was worth 50 hp.

But you have the length, diameter, shape and quality of the bends at play here also.

Wow!