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  #1  
Old 09-11-2008, 06:12 PM
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Location: Springfield OR
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low cylinder compression

I've got 71 2.8 mercedes 6 cyl with low compression (130) in just one cyl,
compared to 140-150 in the others. Unfortunately cyl on either side of the low are 140 and 150, worried about that imbalance . Overheated at some point- machined the head, new gasket ,no valve work just re-set. Walls of
cyl #5 are not nearly as clean as the rest

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Old 09-11-2008, 06:24 PM
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Location: Cicero, Hamilton County, Indiana about 30 miles north of downtown Indianapolis
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There is no im-balance there

You are close to the 15% allowable difference in compression between cylinders. One cylinder is slightly less efficient as you read it then the others. But it is still putting out a lot of power. If you just did the head work described, I would begin to drive it and get some miles on it. Then ninety days down the road check the compression again. You might be surprised at the reading you get.
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Old 09-11-2008, 06:30 PM
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Quote:
Originally Posted by 250taylor View Post
I've got 71 2.8 mercedes 6 cyl with low compression (130) in just one cyl,
compared to 140-150 in the others. Unfortunately cyl on either side of the low are 140 and 150, worried about that imbalance . Overheated at some point- machined the head, new gasket ,no valve work just re-set. Walls of
cyl #5 are not nearly as clean as the rest
Did you rering it ? If not try using some engine flush and retest after an oil change.
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Old 09-11-2008, 07:57 PM
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Retorque the head and then do a comp test. Then do a leakdown test.
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Old 10-02-2008, 06:39 PM
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great thanks for all the help!

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