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New engine compression test

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Best Answer colinlucas , 05-19-2017 08:59 PM

Took the head back to the machine shop. Some valves were leaking, thus the drop in compression. :/

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#1
colinlucas

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Hey everyone!

 

Got my engine bits back from the machine shop and assembled / installed. After bringing the engine up to temp for the first time with some rotella diesel oil I thought I would do a quick compression test. The results are:

 

#1: 120

#2: 110

#3: 120

#4: 120

 

Also, there was some carbon on the #2 sparkplug. So the questions are:

 

How much do you worry about a compression test before the rings are even set? Is #2 compress or the carbon worrisome or will it go away after the rings are set?

 

Thanks!



#2
speedengineer

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Seems low.  Compression shouldn't change much after engine break-in, even if leak down is a few percent worse on fresh motor.  I would try a leak down test.

-Have you used this gauge on another engine and it read normal?
-You sure cam timing is set correctly?  That can have a large effect.
-Correct compression test procedure:  Warm engine, fuel disabled, throttle open?  How many cranks?


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#3
colinlucas

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✓  Best Answer

Took the head back to the machine shop. Some valves were leaking, thus the drop in compression. :/






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