289 compression
Fleet Mechanic
Joined: Nov 1999
Posts: 1,415
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From: Lower 48
289 compression
You guys are talking about 2 different things. Compression ratio is not the same as the compression reading on each cylinder. I don't know what it should be either.
Trail Rider
Trail Rider
Elder User
Joined: Jan 2000
Posts: 966
Likes: 2
From: Crooked River Ranch, OR
289 compression
What's important about doing a compression check is not the amount of PSI reading, but how close all cylinders are together in the range of readings you get. An engine in good shape will have all cylinders read within 10-15%, for example on a 6 cyl. you may have 4 cylinders reading 130-135 PSI, one cylinder at 125 and one at 120. This engine would be O.K. An engine in poor shape would have one or two cylinders reading much lower say 60 to 80 PSI or even lower yet. At this point you would have at least four things that would contribute to the low reading; 1. blown head gasket, 2. something wrong with the valves in the low cylinders (burnt,sticking,weak springs,etc.)
3. worn or broken rings 4. excessive detonation (broken piston ring lands, or hole blown in piston.)Deen
3. worn or broken rings 4. excessive detonation (broken piston ring lands, or hole blown in piston.)Deen
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