Header Collecter Extensions
 

Just wondering when using a collecter extension like a 12" or 18" how much difference on HP. & TQ.? I have a 9.5 to 1 comp. 502 BB dualplane intake, 2" primary headers and 3.5" collecter. It made 621 tq. @ 4500 and 621 hp. @ 6100. The car weighs 3200 lbs w/driver and has a 4:10 gear and turbo 400 trans. It has run 10.07 @ 131.65 mph. If I use one will it make more tq and hp? It has merge collecters on the headers. Also I run a small tire 29.5/11.5-15.

Re: Header Collecter Extensions
 

It's not uncommon to get .03 to .05 performance improvement from the correct length collector tube. Can't say what that means in HP or torque.
I have only used the old paint stripe on the tube, and cut it where the paint changes color, to determine the "correct" length.
Start with about 18" on there and cut it after a few passes to get the length.