I changed the spark plugs today and decided to do a compression test while I was in there. Here are the results:
1. 160
2. 160
3. 170
4. 170
5. 160
6. 160
I guess this engine is in better condition than I thought.

It still uses oil but no puddles under the truck or no smoke.

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1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

Excellent!

Lou

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Home of Slant6-powered fun machines since 1988

Those are some good numbers!

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If it was easy, everybody would be doing it.

I did the same thing today as part of diagnosing my starting issues - thought I may have had a compression issue in #1 while trying to find TDC. My numbers weren't as high, ranging from 140-150. My spec material states 130-160 with a max variance of 20 so well within range and tolerances. Only concern is that I may have a leak in the valves as my vacuum/pressure gauge doesn't stay put on the compression stroke, and I can clearly hear a hiss coming from somewhere. Does anyone have any idea how to tell if it is indeed the valves or the piston rings? I suspect the valves as the engine had been running very rich so lots of carbon buildup!

Here's a video of the sound - #1 is closest to the camera. You can hear the hiss once the intake closes (2nd valve from camera), and the compression begins. Video

FYI there are no spark plugs in any other cylinders so the only hissing is coming from #1.

Thanks as always!

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1966 Clark Cortez Motorhome w/
Industrial Slant 6 looking for adventure!