About a year ago I saw some tech tv show on race cars. Anyway they had 1" x 6" rectangular exhaust pipes to correct the clearance problems. Has anyone ever thought about this approach versus a circular pipe.

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1990 Formula 350, dual cat, aluminum driveshaft, AC delete, TES headers, Flowmaster, K&N 1000CFM, MSD, Hypertech, 3.73 gears, ROH 17x9.5 x (4)

 

I believe they have those in NASCAR for the high speed ovals, due to the downforce reducing ground clearance. Round is the best cross section. The more you depart from that, like flattenig, you will get less flow area for the same inside surface area, or else, a whole lot more inside surface area for the same flow area. In either case, it's less efficient than a round pipe. Those flat exhausts are for special cases, where there is no other way. The f-body just doesn't have room for an efficient dual exhaust unless you drag it on the ground under the floor pan. So many cars nowadays, including ***** 4-bangers, have dual or quad tips, but only a single exhaust pipe, so what's the point?

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1985 Yellow IROC-Z 5.0 HO, T-5 3.73 Posi, 4 wheel disks
PFCM pads, GTA wheels, Koni yellows, B&M Ripper, Dynomax

 

The best thing you can do is stick the biggest single pipe from the back. Another choice is a side exit exhaust. asfar as I know they dont have any prob with draging.

 

Ive got true duals under my 85.

2.5" with long tube headers with spin tech muffers. Havent rubbed 1 time. YET