Compression Test Results - Uniform but Low?

[DeltaT]

I tested my compression today, cranked about 4 seconds per cylinder.

Results were pretty consistent in a range from 92 to 112. Exact numbers were 92, 93, 97, 100, 100, 112.

This is an 87 GN, around 124,000 miles.

How do these numbers compare to a newly rebuilt and broken-in motor?
Thanks,

Jim

 

[mikestertwo]

Kind of low. A motor in good shape should be in the 150-160 range

 

[TurboBob]

did you block the throttle open when testing?

B

 

[buickruss]

Motor warm or cold?

 

[DeltaT]

Motor cold, throttle untouched (closed).

Thanks,

Jim

 

[earlbrown]

There's you problem. Pin the throttle open and run the test again.

 

[DeltaT]

Arrrgh, OK thanks. It wasn't too painful. I appreciate the advice.

I'll post back tomorrow with results.

Jim

 

[1KWIKSIX]

Hey Jim, I know it's already been posted, but wanted to remind you to be sure to warm up your engine first before checking your compression. Otherwise you really won't get a true reading. Throttle Wide Open during cranking too!
Please let us know what your results are afterwards.

 

[gunslinger]

Even with a cold engine, and the throttle closed, these numbers are way too low.
How does it run?
How many times are you letting the engine turn over when you're testing?
If numbers you posted are peak readings, I would expect the engine to barely run. And since the numbers are uniform, I would suspect that the timing chain jumped, and cam timing is off.

If the engine runs okay, I would try a different compression tester.

 

[Fast4Ward]

i would go another few seconds and watch the guage. it does stop at its peak.