ifitgoesfast

1964 Corvette 327 CID / 365 HP

Can 2" side exhaust pipes be adjusted to fit 2.5" manifolds? I bought a set and then later learned the engine I have has 2.5 inch exhaust manifolds. Can they be adjusted, or flared to fit? Do I need some kind of adapter? Any help would be appreciated.

Also, are the side covers of different sizes for 2" and 2.5" pipes? Or are they all the same, regardless of these two pipe sizes?

KC John

I could be wrong, but I think the flange is the same size on both the 2" and the 2.5". The actual pipe is the only thing that changes.
The side covers are all the same.

Fawndeuce

The ones I just bought from Allen's have a step down for the 2" manifolds on my '67, I thought All the SB side pipes were 2 1/2" OD?
Are you sure yours are only 2" OD?



Paul

wmf62

any good muffler shop can make a new end piece to mate up the exhaust pipe to the manifold.
Bill

JohnZ

'65 SB sidepipes came two ways - 2" manifold connection or 2-1/2" manifold connection, depending on the engine; '66-'67 SB sidepipes only had one flavor - 2" manifold connection. All sidepipes (SB & BB) used the same straight muffler section (1-7/8" inner pipe diameter).

ifitgoesfast

I assume it was the L76 365 HP engine that called for the 2.5", and I'm guessing that was necessary because of the higher compression (11:1)?

Is it the L76 engine which had the 2.5" manifold that a 2" pipe connection would not fit? I'm trying to decide if I should make this work somehow, or just sell them.

wmf62

it can be easily made to work, don't fret about what engine had what... as John said:
All sidepipes (SB & BB) used the same straight muffler section (1-7/8" inner pipe diameter).
Bill

MikeM

To answer your question, in 1965, only the 250 horsepower base engine used the 2" pipes. The 300, 365 and 375 used the 2 1/2" pipes.

I believe I would rather have my 2" diameter downstream in the sidepipes as the exhaust cooled and contracted rather than in the hot, expanding, exhaust coming out of the manifold.

JMO. Maybe GM engineers know different?

ifitgoesfast

Can I just bolt these on or do I need some sort of adapter for the pipe to manifold connection. I currently have the regular under car rear pipes install. Before I remove them, I want to make sure this can work.

(btw, the car had small side pipes in the 70's, someone already cut off the body and bracket)

MikeM

Your car does/should have 2 1/2" manifolds. The pipes you bought have 2" inlets. You NEED TO DO SOMETHING here to make them fit.

You can probably have a muffler shop cut off about six inches of your pipe and weld on the same length and 2 1/2" diameter connector to your manifolds.

Go see Midas. They can be your friend.

wmf62

gee Mike, i suggested that twice... maybe he will listen to you...
Bill

ifitgoesfast

Sorry guys, wasnt paying attention. Thanks for the direction.