| parrish | -- 06-28-2011 @ 11:43 AM |
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I've always read that one should remove all plugs and used open throttle to test compression, which is what I do. If I want to test only one known low compression cylinder, will I obtain an accurate historical reading with only the one plug removed? Thanks for the help.
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| supereal | -- 06-28-2011 @ 2:09 PM |
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The reason to remove the plugs is to allow the engine to crank at maximum speed. I usually forget to prop the throttle open, but it doesn't seem to make much difference. It is a good idea to do a dry test, then squirt some oil into the cylinders to see if the compression rises. If it does, the rings are worn, if not, the valves are leaking.
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| Stroker | -- 06-28-2011 @ 2:10 PM |
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Parrish: In theory yes; however a couple of caveats: 1. Your starter will not spin the motor as fast, so you will possibly be comparing "apples-n-oranges" if you are not used to counting revolutions. Just make sure you get a representative reading by letting it turn over at least as many times as you would normally with the plugs out. The cylinder won't "pump-up", but sometimes the first revolution may not have "gulped its' breath" fully after you propped the throttle open. 2. Make sure the ignition is off!
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