J-Rod

Does anyone know where there are calculations for headers? I have been able to find the ones to calculate priamry length. My question is more along the lines of when doing a stepped header, how to figure how long tube a needs to be before stepping down to tube B, etc...

Also looking for the same formulas for calculating intake manifold plenum size, and runner length.

Thanks.

Old SStroker

You might try Scientific Design of Intake and Exhaust Systems by Phillip H. Smith.

There isn't necessarily a "one size fits all" formula for exhaust, especially stepped headers. Some hgher end simulation programs give some help, but it's more results than design. The programs are better with intake than exhaust. Length, area, taper and flow coefficient are addressed.

More importantly, IMO, is whether to use 4 into 1 or 4-2-1 headers. 4-1s are easier to build and probably less sensitive to tuning lengths, but many of the high-end series like Pro Stock and Winston Cup use 4-2-1s.

If I were building a header instead of buying one, I'd seriously consider 4-2-1. There is at least one company that will build you 4-2-1s on your car and tuned to your engine. The bad news is nearly "3 large" to have it done!