Im sure this has been asked and aswered a thousand times by now, and yes I used the search bar and no info. Anyways, I built a mild 355 for my car and installed it this summer. Im still running a crappy 2.5" OD to a blowmaster crossflow. I am wondering if anyone has, or know of a flow chart for cat backs for our cars, or the best flowing exhaust. I am not worried about exhaust tone, I just want the best flowing exhaust made for our cars. (Btw, i know mufflex and hawks makes 3.5 - 4" exhaust, but i am wanting a 3")

Specs:
9.7 - 10:1 compression
350 4 bolt block .030 over
GM performance Steel crank
Eagle H beam rods
Speed pro flat tops 4 valve reliefs (Hyper)
Ported Vortec Heads (1.94/1.5 valves)
Stainless valves
Edelbrock Sure Seat valve springs
1.5 Rockers
Comp Cams 270H Magnum cam (.470/.470 lift, .270/.270 duration)
Procomp port matched High rise dual plane polished (Performer RPM style)
Carter AFB competition series 650 CFM
Summit Street/Strip HEI
Clyotes True double roller timing chain
Melling High volume oil pump
Manley Push rods
Melling lifters
Summit headers
Custom 2.5" y pipe
2.5" intermediate
Flowmaster muffler
Tremec T5
Zoom clutch / pressure plate
3.23 non posi rear end

I am guessing this motor is capable of 380 - 400 crankshaft HP, with a good tune and a few little mods. It roasts the tires pretty nicely in 2nd and part of 3rd. Currently on 215/15 firestone indy 500's sadly, but saves the tranny.

 

I've never seen more than just a muffler flow numbersand the further back in the exhaust the muffler is the lower the flow need to be...

 

Thanks for the reply. I heard the flowmasters tend to flow really bad, and magnaflows flow decent and same with the hooker and SLP exhaust. So , with my mods, what exhaust should I run.