Header primary size - 547 A460 engine

Gents - I posted some Dyno results last week for my 547" A460 head engine. We only pulled the engine to 7000 rpm which is where we saw peak power of ~930 hp. My Fox mustang headers wouldn't fit the Dyno so we used a set of chassis headers which were 2 1/4" primary x 4" collector. The headers I have for my car are 2 3/8" x 4". Are the 2 3/8" tubes too large for my application (2900# non-nitrous car)? Thanks for you help.

2-3/8 is bigger than I'd want.

X2,the 2 1/4 is bout right.

I am thinking the same. I have too much invested to give up power just to use a set of headers I have on hand... I will build new ones.

Know anyone looking for a nice set of HPC coated 2 3/8" Fox body headers? Headed to the "stuff for sale" section.

How long are those 2 3/8" primary tubes...?

IF they are made 28 to 31 inches long, you could sane yourself quite a bit of time by using a large step with 2" tubes for about the first third of the length and use most of your present headers; (unless the port itself would be to big for 2").

There would not be any difference in power to see with those 4" collectors.

Thanks everyone.

The headers will be in the 28-31" range you mentioned. IF I need to just build new headers what would you recommend? Primary tube size? Step vs no step? Collector size?

Thanks again

here is a whole lot more to it than maximum horsepower. RPM power range and almost everything about how the vehicle ACTS is very important.

The figures I gave you would act like a 2 1/4" straight tube header ... whether that 2 1/4" into 4" is the correct size or not is to be determined.

why not try what you have ? You may lose some bottom end , but that may help with starting line traction

Thanks, I think that is a good point especially since this is going in a stock suspension 10" tire car. I think I will do that in the interest of testing, and then modify them over the Texas "winter" to include a 2 1/4" step. Thanks again.