Hey guys,
I am going to be running a 383 with 180cc AFR heads, Hot Cam, and HSR system. I will be running ceramic coated long tube headers with true duals and two high flow cats. Just trying to see what size primaries ya'll think I should run, 1 5/8 headers or 1 3/4 headers and this will all be going on a Truck. I was thinking 1 5/8's to keep some low end to the engine however since they are long tubes they help all over the power band so 1 3/4 might not lose any low end. Thanks.

 

1-5/8 will be good, 1-3/4 will be better.

 

Roughly speaking, at what point (in hp) do the 1 5/8 primaries become a restriction?