Thread: 350 small block knock at idle rpms

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Couple more questions. Automatic or manual? Does it do it in gear or in nuetral or both? Could it be the torque converter, or a loose torque converter bolt if it is an automatic?. Have you gotten under the car to try to locate it? Have you had the carburetor or intake manifold off lately? Any chance something small could have fallen into an intake port and is sitting on top of a piston? (been there done that with a piece of a cotter pin. Made a knock like you decribe. But my knock did not go away above idle).

One thing to try is a mechanics stethascope to try an locate it. if you don't have one, a long extension or breaker bar placed right by your ear and then the other end moved around against different parts of the motor will transmit the sound. Just be careful around moving parts.

As for the overheating, describe what you mean by high speed, and how long before it over heats?

Pat