I'm replacing the headers on my drag car. It has a 383 650 hp 2600lbs race ready 5.14 gear. Had 1 7/8" with 3.5 collectors. I ordered new Kooks stainless headers they are 1 7/8" but 3" collectors. The collector looks really small compared to the 3.5. The headers are a fair amount longer as well. Is 3" collector big enough for 650hp 7000 rpm drag car no exhaust? Thanks

This message has been edited. Last edited by: inferno camaro,

I'll throw out that my 6.2 LS, 376 cubic inch, making roughly the same hp, uses 1-7/8 with 3" collector, as well as many stroker LS' using the same header, making more than 650hp, even 700hp+

I think your primary tube is already on the large side.
On a merge style collector the 3" wouldn't bother me, but I think 3 1/2" would be more appropriate.

My 1 3/4" primary tube headers are 3 1/2" collectors.
I have no real science to back up my opinion.
There was a Jere Stall site that had a lot of science on it...don't know if it's still live.

Check that, here is what it is now.. https://www.acpheaders.com/