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71 Eldorado - Engine Compression

704 Views 2 Replies 2 Participants Last post by  Billibob48
Just checked my compression and it's 145 lbs on all eight. Does it need an overhaul or is that normal for 70K miles? Shop manual specs are 165 to 180.
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Warm up the engine by driving 15 miles, shut down and block the throttle wide open. Disable the ignition and recheck compression.

All 8 at 145, cold, is pretty good. Warm, if you check compression and several cylinders are not within 10% of the others, dribble in a half teaspoon of engine oil into each cylinder and roll the engine over several revolutions. If compression rises materially, worn rings. If it stays the same, worn valve seats.

FWIW, one of my Olds 455 marine engines will show 150 - 160 psi, hot, with a compression ratio of 9.7:1. (We build them to run on 87)
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thanks so much for the info. I think I'm going to hang my hat on "All 8 at 145, cold, is pretty good." If i start to have additional problems though I'll know what to do.
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