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9/24/13 12:29am - Original Message: '69 BB exhaust size'
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Kalispell, MT - USA

1969 427 sport coupe, Monza Red, matching numbers, all original.

Joined: 2/28/2013
Posts: 10
Maybe a newbie question....but I am!
Why is it that my 427 goes from 2 1/2 inch down to 2 inch from the manifolds?
Why wouldn't they, (Chev), open the whole thing up and make it 2 1/2 inch all the way to the back? Heck...it's a big block!
Also, I have new front and intermediate pipes coming from Corvette Central. Looks like the originals were clamped. Should I use clamps or is it ok to weld them and still be okay with the NCRS folks?
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9/24/13 6:30am - Reply: 'Re: 69 BB exhaust size'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19542
Most, if not all, low HP engines used the 2" exhaust. The higher HP engines went with the 2 1/5" exhaust, but all engines had the 2 1/5" manifold outlets.

If you plan on doing NCRS Judging, it's best to use the same type of fastening as original. Without looking at the AIM, I couldn't say which way yours was originally, but it's safe to say that the head/intermediate pipes were most likely clamped. Some years had mufflers welded to the rear pipes, some were clamped....same with the exhaust extensions/outlets....some welded, some clamped. 

Joel Adams
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9/25/13 11:50am - Reply: 'Re: 69 BB exhaust size'
F4Gary Gold Member
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Grapevine, TX - USA

1972 LT-1 convertible with factory air.

Joined: 8/26/2006
Posts: 943
60 mph
26" tire
2.73 rear end

=2100 rpm


A 3.55 rear end would get you 2800 rpm.

As you go up or down the rear end ratio list, each step adds or subtracts about 200 rpm.

|UPDATED|9/25/2013 9:50:05 AM (AZT)|/UPDATED|

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 Forums -> C3 Fuel, Emission Control, and Exhaust Systems
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