Collector Size

I have a 394 ci motor and Pipe Max said to run 1 7/8 primaries and 3 1/2 collectors. So that is what I built. Mine is a pump gas motor and runs 6.20' s in the 1/8 @ 110 mph.
X2!!!
If you want an exhaust system that is tuned to your eng. PipeMax program is a good place to start.....and finish:D