Race header sizing
 

I'm getting ready to have another set of headers fabricated for my car and I wanted to get some knowledgeable opinions on header size. My current headers are stepped 2 1/16" to 2.25" primaries. The combination is in my signature below, but the engine is 541 CI, and I shift around 7800 rpm. HP is around 1050. Does anyone else have a similar combination, and what size headers are you running?

Tagging on - Always good to hear opinions and possibilities of facts.

OK, I spoke with Jeff at KRE and he recommended starting with a 2 1/8" primary for around 12-15", then stepped to 2.25", then to a 3.5" merge collector. Any thoughts on this?

This is a Trans Am series car. 358 cu in engine, 935HP @ 8600rpm. 2.25 inch pipes into 2.5 inch pipes into 3 inch Y-pipes into 4 inch side pipes.

We swapped out the engine in just over two hours after it had lost coolant pressure in the last 15 minutes of a practice run. Big increase in crankcase pressure the next time out indicated rings were toast. It was only a $60,000 muck up.

Then pinion bearing gave out during qualifying and we had to swap out the carrier the night before the race. Hypoid gear lube is an excellent skin softener.

I'd try Larry Meaux' Pipe Max and see what it says?
Just a rough estimate I'd think it would need a little more?
(need a lot of engine specs to use it)


:confused:

2-1/8 for around 4” to 2-1/4 to 2-3/8 total length under 28” into a 4” merge collector. Clocked for firing order

A FWIW, John's combo in my signature uses 2 1/4- 2 3/8 step header, 34 primary length, 4.5 collector.

526 CID
4.500 / 4.315 / 6.7
HP heads / 13.2 :1
Victor intake w/Cloverleaf spacer & sheer plate
8896 Dominator carb
920hp at 7000 rpm


.

Exactly what I was looking for. Thanks!!

That's what I'd do

Here are my SS headers. Very close to what John suggested. I run 2.125-2.25" and merge collectors clocked to firing order at 900 to 950hp depending on combination in car.

WOW Nice and great fitment too

GT

We tried 2 different sets of headers on the dyno.

2"-2 1/8" 947HP

2 1/8"-2 1/4"-2 3/8"-2 1/2" 963HP

Thats a pretty good jump, wouldn't of exspected that much from a step
header.

GT