1973 Plymouth Valiant Uneven Compression

PLYMOUTH
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RAINEDOUT2000
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I was given a 1973 plymouth valiant. I checked the compression from front of the engine to the back was 90, 90, 90, 0, 90, and 155. What could be the problem?
Mar 10, 2006 at 12:03 PM
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JACOBANDNICKOLAS
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The engine is worn out. It needs to be rebuilt. The 90 PSI is very low, 155 PSI is normal, and the 0 PSI concerns me. It could be a bent or stuck valve, a hole in the piston... You need to pull the head off to check for the cause.

Let me know what you find and we'll go from there.

Joe
Mar 22, 2009 at 6:45 AM
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Suggested Repair

The engine is worn and needs a rebuild. Remove the cylinder head to find the cause of the 0 PSI reading, which may be a bent or stuck valve or a hole in the piston.

Conversation Summary

The owner of a 1973 Plymouth Valiant reported compression readings of 90, 90, 90, 0, 90, and 155 PSI from front to back. The expert said 90 PSI is very low, 155 PSI is normal, and 0 PSI is a concern. The engine is worn and needs a rebuild; the zero reading could be a bent or stuck valve or a hole in the piston, so the head should be removed to inspect the cause.

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