Noise Question

[Bernie]

Thanks again for the responses. Here, I think, is the end of the story. I probed all around with the end of a tube to my ear. I couldn't find any one place, like the timing cover or the flywheel cover, that the noise was coming from. I did find that the bolts attaching the exhaust to the manifold were a bit loose so I tightened them and the noise became less. I set the timing correctly and the noise got less. I replaced the vacuum line to the right hand outlet (looking from the front) of the carb (Edelbrock 1406) this is the port with constant vacuum, and the noise got less again at higher revs. It is now at a level that is ok. I had put the bigger Corvette manifolds on and had a new exhaust made with turbo-flow mufflers. It sounds to me that the noise is some sort of resonance in the exhaust.