Compression in merc 420's
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Compression in merc 420's
What should the cranking compression be in 1989 Merc 420's ? and how many hours of run time before they should be rebuilt ????
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Compression ratio when new is 8.8-1. I would do a leak down and compression test. When the leak down # gets high you need to think about rebuilding or doing a cylinder head rebuild.
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