C3 '77 Exhaust Leak

[jim34671]

Just fired up a newly built 350 in my '77. (L48)
There seems to be a very pronounced exhaust leak coming from the vicinity of the
carburetor.
Exhaust/Intake manifolds tight and fine.Exhaust pipes tight.Donut changed.
EGR and choke heat tubes fine also.
The engine was recieved as a short block and I built up the top end.
It runs fine above idle,yet this exhaust noise quite noticeable.
Is there anything I may have forgotten during intake manifold installation?
I simply laid down the 2 intake gaskets and torqued the manifold in place.
It's a stock GM manifold.
Thx
Jim

[Joe L.]

Re: C3 '77 Exhaust Leak

Jim-----

If the leak is not originating from the EGR valve or its gasket, then the only thing that I can think of that would cause an exhaust leak in this area would be a crack or similar defect in the intake manifold exhaust crossover passage which supplies hot exhaust gas for choke and EGR system operation.

[Joe G.]

Re: C3 '77 Exhaust Leak

Jim,

You mentioned laying down 2 gaskets. There should be a front, a rear and two sides for the intake manifold. Could this be the problem?

Joe

[jim34671]

Re: C3 '77 Exhaust Leak

Joe,
I only use a good bead of silicone for front and rear.
Jim

[jim34671]

Re: C3 '77 Exhaust Leak

Joe,
Is there a chance that an A.I.R.tube missing would do such noise?
Both EGR gaskets replaced.
Jim