Cylinder compression issue

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
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hohenstaufen9
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Cylinder compression issue

Post by hohenstaufen9 » Sat Sep 10, 2022 7:23 am

Hi gents,

Not long ago, I replaced a blown head gasket on my F head. It’s a rebuilt engine (supposedly). It was running fine for a few hundred miles. One day, on a longer than normal run at higher RPM, I suddenly lost a bit of power while pulling up a hill. And started to hear a rattle at idle.

Did a compression test yesterday with the following results:

#1 dry 110 / wet 125
#2 dry 112 / wet 122
#3 dry 100 / wet 105
#4 dry 80 / wet 90

I’m guessing not rings, but any other opinions are appreciated!


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dpcd67
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Re: Cylinder compression issue

Post by dpcd67 » Sat Sep 10, 2022 12:21 pm

Rebuilt means brought back to factory new condition in EVERY respect. So, was it actually rebuilt, or just overhauled?
I would retorque the head, check tappet gaps on the valves, and drive it. I've driven jeeps with less compression.
Just read the term Rattle; that's not usually good. Where are you? I'll look at it.
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hohenstaufen9
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Re: Cylinder compression issue

Post by hohenstaufen9 » Sat Sep 10, 2022 12:57 pm

Yes, a rattle at idle. Hard to tell from where. The prior owner passed away and only info is supposedly it was rebuilt. When I got it, it had a head gasket leak on #3. I cleared that up along with adjusting valves. Re-torqued the head a few times. Got nearly 500 miles on it before this happened.

I’m in Northern Cal.


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