I've got a 1960 Buick 401 with a confusing problem that maybe one of you have seen. The engine was running perfect and then one day the engine noise was different. The engine noise appeared to be exhaust and was traced to an area under the intake manifold. I assumed it to be a blown head gasket, but after replacing the head gasket the noise remains exactly as before. Both the head and block seemed within tolerances and did not require shaving. I would appreciate any thoughts you might have as to potential causes of the problem. Please send your ideas and suggestions. Thanks
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