Header primary size - 547 A460 engine

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Header primary size - 547 A460 engine

Post  Rich Osmond on August 29th 2013, 8:07 pm

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.

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Re: Header primary size - 547 A460 engine

Post  Lem Evans on August 29th 2013, 8:21 pm

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

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Re: Header primary size - 547 A460 engine

Post  bbf-falcon on August 29th 2013, 8:49 pm

X2,the 2 1/4 is bout right.

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547" headers

Post  Rich Osmond on August 29th 2013, 10:29 pm

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.

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Re: Header primary size - 547 A460 engine

Post  rmcomprandy on August 29th 2013, 11:41 pm

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.

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Headers

Post  Rich Osmond on August 30th 2013, 8:15 am

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

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Re: Header primary size - 547 A460 engine

Post  rmcomprandy on August 30th 2013, 4:58 pm

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.

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Re: Header primary size - 547 A460 engine

Post  v-twin on September 4th 2013, 1:32 am

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

Post  Rich Osmond on September 4th 2013, 9:22 am

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.

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