[PontiacsForLife]

Hey guys, I want to get a new single exhaust system for my '62 w/a 1bbl 4 cylinder. The original pipe is very small, and if this pipe isn't the ideal size, I'd like to make it optimum. My priorities (in order) are a quiet car, followed closely by a small performance gain. Does the small diameter pipe make it quiet?

-Adam

[mechanickeith]

Small pipe does not make it quiet. It is a restriction & causes a severe loss of power. The muffler makes it quiet.

If my memory is correct, the inside dia at the outlet of the exhaust heat crossover adapter is 1 7/8 inch , 1 7/8 into the stock muffler & 1.5 inch from muffler to end of tail pipe. I have 2 cars that I have opened up the adapter outlet to 2 inches & ran a 2 1/4 inch pipe all the way out the back with a turbo muffler. Both are nice & quiet & made quite a bit more power. I did have to adjust the tune some for the less backpressure system.

I have 1 car that I removed the heat crossover all together & ran a 2.5 inch pipe from the exhaust manifold out to just in front of the right rear tire with a cheap glasspack. Quite a bit louder & ran much better.

I have also ran several with different style of headers. Most power I got was from a set of home made tri-y's I built. 1 7/8 primary pipes into 2 inch into 2.75 collector.

[PontiacsForLife]

Rather than modifying the butterfly valve, I'm thinking about using a Pontiac 350/400/455 D port (standard) exhaust manifold and blocking off the exhaust crossover port under the carburetor. Do you forsee any problems with this plan? Will a Firebird/Bonneville/LeMans exhaust manifold be less restrictive and match the (essentially) 389 head?

-Adam

[mechanickeith]

Tha butterfly valve is in the manifold, not in the exh crossover adapter that bolts to the manifold. You can do it as you describe, but, if the car is driven in any cold weather it will be a real bear to get warmed up if you delete the exhaust crossover.