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1970 Chevrolet Pickup - Stuck valves or rings?

I’m working on a chevy 283-v8 that sat several years after being removed from 56 chevy. Date marks on block are April, 60. Engine turns free without noise, but compression check shows # 4, 7, and 8 have near zero compression. Others range from 30 to 135. Are valves or rings stuck from storage?

Probably. Engines that old are likely loaded with crud. Best would be a complete tear down, block and heads machined and engine rebuilt. But you could try squirting a bunch of light oil like Marvel Mystery Oil or transmission fluid into the cylinders, along with fresh oil in the crankcase, let it sit overnight, then spin the engine with the spark plugs removed. See what you get then.

Pull the valve covers. Rotate the engine. Do all the valves close? No? Stuck valves. If they all close, then rings.

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Do a leak-down test on those cylinders and you’ll find out why they have low compression.

https://www.pegasusautoracing.com/document.asp?DocID=TECH00137

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