Question on header diameters..

[C&C Chevy]

1 1/2", 1 5/8", 1 3/4" These are the most popular primary tube sizes for headers.

What's the difference for each primary tube size? What's the best application for each? Is bigger always better? Just curious.

[f.monroe]

I am sure someone will give you a more specific answer but bigger isnt always better . A stock engine wont perform as well with a larger diameter header as a well built engine . Too large of primary tube will not provide enough back pressure and will cause problems . I have heard of engines running hot due to using too large of a primary . If your engine is stock to mild , I would use the regular 1 5/8" tubes . Frank

[SSC's76]

Wow mention of 1-1/2" headers, thats a small pipe not suitable for anything over 300 cu or with any modifications.

A stock/mild 267-305 will usually be fine with 1-5/8" headers, step up to a cam with over .400 lift and your going to want the 1-3/4" headers. A 327-400 will benifit most from 1-3/4" even stock smog engines. Usually 1-3/4" will flow well for an engine to the 400 hp range then you step upto the 1-7/8" might even want to go to the 2" or the 2-1/4" after that.

[magnethead]

it think mine has 1 7/8ths" primary's....

[C&C Chevy]

That sucks about the 1 1/2". Seems like most of the headers under $150 are 1 1/2" primary kind. I guess I'll start looking for a 1 3/4" primary tube header.

[Karl Hoh]

Smaller primary tubes help low end torque. If your engine is stock or very mild, I would run 1 5/8. We ran 1 3/4 and 1 7/8 on a 480hp camero bbc drag car. My 2 cents.