Big tube header vs small tube header on a stroker

tubbedamx said

I would imagine that would depend on cubic inch and Rpm out the back along with the length of your header extension

on my 390 (630hp) I changed from 1 7/8 with 3 collectors to 2 inch with 3 1/2 collectors and I didn’t see any improvement on the dyno until 6800rpm to 7500. And it wasn’t much.

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I dont doubt you wouldnt see a difference with the above factors.1 7/8 headers are plenty for anything Indy head on down
I put a 3.5 inch collector on a 700 horse W5 motor and saw nothing compared to a 3 inch collector( 1 7/8 headers). Ran 140 mph@3220


my motor will be a 12 to 1 418 with decent eddie heads and a flat tapper cam. I race a lot. The 1 5/8 headers were on my stock stroke 360