383 engine noise question

buck351 said

It is synthetic ZRod Amsoil not regular 20W50. Didn't know how 10W30 synthetic would get along with a vintage engine since it flows easier than regular 10W30. For about 40,000 miles before the rebuild I had a different cam and Rhoads lifters which at the time required 20W50, 40 or 50 weight. I ran 20W50 and it was non synthetic. Never checked the pressure back then.

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First, I'm inclined to agree with mguner's assessment of the noise...probably just some loose tolerances if your oil pressure is adequate and you've run down the other likelihoods (lifters, fuel pump, etc.)

The reason I quoted the above statement is because of my own potential misunderstanding. If I understand the rating of oil viscosity correctly, the brand and type don't matter because they're formulated to operate under the viscosity rating on the bottle and the API service rating on the back (I think they're up to SN now). The viscosity of the oil used needs to match the engine build though...thicker oils will create more demand on the oil pump and driveshaft and probably shouldn't be used unless the engine needs it. Thinner oils create less drag but aren't well-suited for large bearing clearances because the volume required to hold the wedge would kinda defeat the purpose of using a lower viscosity oil in attempt to reduce parasitic losses.