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Thread: Compression No's

  1. #1
    Defender of the Normal John Fusco's Avatar
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    Compression No's

    Just did a compression test on my 2.2 normal.
    95's all around.
    I know that it's good that they're all the same, but is 95 a good number to be on ?

    Thanks

  2. #2
    It's good that the numbers are consistent. They do sound low. If I'm not mistaken a tight engine will be in the 125-175 range give or take. Did you do the test properly?

    Check your valve adjustment first. For the comp. test warm up the engine and make sure you hold the throttle wide open when you take the readings.

    Most people will tell you that a leak down test is more informative.

  3. #3
    Defender of the Normal John Fusco's Avatar
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    I didn't have the throttle open.

    I've been having backfiring out the tailpipe and some lurching while running and was afraid it might be a valve. It appears to be spitting out the back left weber throat.
    The plugs all looked good and they all have new wires - new distributer.

    Noticed there is a wire coming out from where there are wires going to the permatune box, but this one is just hanging . Any idea what that was/is for?

    Thanks

  4. #4
    Even numbers=good. 95 is pretty reflective of a good, but relatively low compression 2.4...all figures variable because of the mechanic, his brand of testing equipment, how he performed the test, etc. Bottom line: Even numbers=good.
    Paul D. Early S Registry #8 - Cyclops Minister of West Coast Affairs
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  5. #5
    Defender of the Normal John Fusco's Avatar
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    I read in the performance handbook that when you convert a 2 liter to 2.2 the effective comp ratio goes down ( around 4/10 of a point )

    What would the comp ratio be for a 2.2 with weber ida's ?
    I am not sure if the cams were changed, or if it was ported out on the rebuild.

  6. #6
    I don't think the details of your engine really matter. Your numbers are consistent, just low. If you redo the test with the throttle open they should go way up. I would put my money on the 140-150 range. Get a helper to rev. it up while you read the gauge.

  7. #7
    Defender of the Normal John Fusco's Avatar
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    sundaypunch;

    Good guess - 150 it is.

    The backfiring has gone away - one of the nuts holding down the left carb was loose, so I fired him.

    Any guesses as to the horsepower on a 2.2 with 40 IDA's ?

    Thanks

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