Thank you for all of the suggestions about my U20 starting to stumble. I
have tracked most of them down and found that the fuel pump is not the
problem. I replaced the distributor cap and wires. No help.
I tried adjusting the airflow screws and found the front carb was not very
effective, but it does effect air flow to some degree. Looking into the
vent holes on the top of the SU carb bowls I can see the floats are staying
up near the top side of the bowls and not flooding.
Next I took the plugs out and noticed that I need to lean it out a bit, but
they are not wet or white. I put a compression gauge on each plug and found
the following:
1 - 155 lbs
2 - 175 lbs
3 - 200 lbs
4 - 225 lbs
These readings were taken without squirting oil into the plug holes, and I
ran them twice to be sure of what I was seeing.
Over the winter the head gasket was replaced to correct an oil leak. I did
not see any major cylinder wall problems in the two cylinders I could look
at, but I did not turn the engine to look at the other two cylinders (1 & 4)
because I did not want to mess with the timing chains.
This engine has been played with by someone, and it will not run well on
less than Super grade gasoline. It still wants to ping if I get on it hard
using Super grade gas. If my memory serves me correctly the head is milled
about .017 if my head measurements and memory are correct.
I suspect that I may be looking at tearing down my parts car engine and
rebuilding it (numbers matching) to replace this one from what I see on the
compression gauge.
Tom
69 2000 "Mr. Hyde"
Portland, OR
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