How about that.. they changed the exhaust diameter from 2.5 to 2 for the 327-350hp

[Steve F.]

Had an opportunity to pickup some nice side pipes for my 65 350hp. Only to find that the 66 350hp exhaust was necked down to 2.0". I turned down the deal because that set of original pipes belongs on a 66. Not to be cut up for a 2.5" 65.

Not that I'm trolling for side pipes, because I'm not.

Seems my curiosity is more inline with why? Why did GM change to the smaller exhaust outlet? Did the 350hp not require the larger pipe? Or was it economics to just use one pipe for the small block and the 2.5 for the big block? The exhaust pipe is "stepped" up from the manifold, 2 - 2.25 - 2.5 from the down pipe to the turn to the side pipe.

[James G.]

Re: How about that.. they changed the exhaust diameter from 2.5 to 2 for the 327-350h

regarding mid years - Only the 66-67 350 HP used the 2- to 2.5" exhaust -
The std engines used the 2" all the way out.
From 65-66 the SB HP exhaust manifolds were changed from the 2.5" outlet and 2.5" pipes to the 2" outlet manifolds dumped into into the 2" swaged down 2.5" exhaust pipes.
Hope that makes sense.
I imagine 1965 2.5" Small block side exhaust pipes are difficult to find, the 65 BB would also be 2.5" however it would have different connections to the exhaust manifolds if not mistaken.

[Joe L.]

Re: How about that.. they changed the exhaust diameter from 2.5 to 2 for the 327-350h

Had an opportunity to pickup some nice side pipes for my 65 350hp. Only to find that the 66 350hp exhaust was necked down to 2.0". I turned down the deal because that set of original pipes belongs on a 66. Not to be cut up for a 2.5" 65.

Not that I'm trolling for side pipes, because I'm not.

Seems my curiosity is more inline with why? Why did GM change to the smaller exhaust outlet? Did the 350hp not require the larger pipe? Or was it economics to just use one pipe for the small block and the 2.5 for the big block? The exhaust pipe is "stepped" up from the manifold, 2 - 2.25 - 2.5 from the down pipe to the turn to the side pipe.

Steve------

As far as Corvette small blocks go, 2-1/2" exhaust MANIFOLDS were limited to some 1962-65 Corvettes including all SHP and L-75 with manual transmission. No Corvette small block before 1962 or after 1965 was ever equipped with 2-1/2 manifolds. Many 1966-67 small blocks, all 1968 small blocks, and 1970-72 LT-1 and some 1973-79 L-82 were equipped with 2-1/2" exhaust pipes and mufflers but NONE had 2-1/2" outlet exhaust manifolds.

All 1965-74 big blocks had 2-1/2" exhaust manifolds and all except 1969 had 2-1/2" exhaust systems. 1969 exhaust systems were 2".

[Steve F.]

Re: How about that.. they changed the exhaust diameter from 2.5 to 2 for the 327-350h

Seems that the 65 L79 is an odd SHP duck in the mid-years. Not uncommon to find. But one like mine with most of the parts intact is a nice example to keep.