I have an 88 Iroc with the 5.7. How wide is the stock pipe going from the cat to the muffler? And how do I tell a stock pipe from a flowmaster or whatever catback?

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-80 Camaro 350, Carter AFB, headers, dual exh, ram air, all sorts of crap
-88 Iroc-Z 350tpi, 3.27 gears, 4 wheel disc, MSD 6a, tpi airfoil, k+n's, white gauges, accel coil, flowmaster, pretty quick

 

I'm pretty sure it's 2 1/2".

The aftermarket quality cat-back systems utilize mandrel bends (all the same size) to employ better flow characteristics over stock regardless of pipe diameter. A good starting point for upgrades is going with a 3" catback exhaust system, and go from there. You will see the difference in pipe diameter, and smoother bends over stock.



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Dan Young
1995 Z28/M6
Groton, CT

1985 Z28/A4
(Prospective purchase)

 

I think its 2 3/4" on the 350 cars.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

I've spent considerable time modding the stock exhausts on both of my '88 L98's and will back-up Kevin. The stock catback is in fact 2.75" O.D. pipe. The pipe after the cat is a heavier guage than the pipe before it(14 ga vs 16 ga, I believe). It takes a while to cut through it with a cut-off wheel if the pipe is still on the car(don't ask!).

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He who hesitates,... is lost!

 

not if you grab a bench grinder with one of those big cutting discs!!

 

I used a 40,000 rpm die grinder with a 3 1/2" cut-off wheel. It took 40 minutes of cussing and swearing to complete the cut, by which time the wheel had 1/4" less diameter. A bench grinder would have been ideal, IF the pipe had been removed from the car, but this was not an option at the time.

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He who hesitates,... is lost!