Bill,
Good work! Now, squirt a bigger bunch of oil into #3 to see if the oil will
seal a bad ring (not likely the problem). If after doing that, you still
measure no difference in #3 compression, the valves in #3 are most likely the
culprit. A bad plug or plug wire could have started this whole mess by allowing
the valve to become fouled until it or they would no longer seat. Regardless,
you will have to pull the head to de-carbonize the combustion chamber and
re-seat the valves.
If that doesn't work, pull #3 piston and connecting rod out the top for service
or repair. If you are after a perfect repair, you will want the engine out for
another overhaul (not necessary).
wcameyer wrote:
> Help[!
>
> Rebuilt my '77's engine a year ago. Have been having some running problems
> lately - rough idle, etc., but seems OK, though maybe a bit weak at higher
> revs
>
> Pulled the plugs, which I replaced a few weeks ago: #1&2 - white, clean as
> new. #3 - black, oil fouled #4 - tan.
>
> Checked compression - #1 - 133, #2 - 136 #3 - zero to five, #4 - 129. No
> appreciable change when I squirted a bit of oil into #3.
>
> Valve adjustment a bit tight on #3, but re-adjusting did not affect
> compression.
>
> OK - What's wrong : gasket, valve, rings, and how do I determine which it
> is??
>
> Need help,
> Bill
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