I'm a recent subscriber, so please bear with me if this topic has been
covered in the past.
I have been monitoring the compression in my TR4 over the past two years,
and am starting to get concerned. During my end-of-season, before we pack
it away, just to make sure I have all my winter projects identified, going
over the car ritual, I measured compression. With the engine up to
temperature (170 F) and all plugs removed, I observed the following:
#1 100 #/in2
#2 170 #/in2
#3 155 #/in2
#4 155 #/in2
All of the plugs had a nice tan/grey color, and there was no evidence of
fouling or oil splash.
A similar set of measurements taken about 18 months ago yielded 135 in the
#1 cylinder, and 160-175 in the other three. The car has about 70K miles
on it.
Clearly I have a problem, hopefully just in the #1. I squirted some 20W
oil in the #1 cylinder, turned the engine over a few times and took
another reading -- came out the same.
Now, I am hoping that I have a bad valve, but I also realize that the low
compression might be the result of a broken ring or some other problem
with the piston. I suppose if I got really lucky, it might be just a
leaking head gasket. Regardless, I will have to pull the head.
Questions:
1. Are there any other tests that I should do before tearing into
the engine?
2. Once the head is off, what's the first thing I should look for
to determine the source of the low compression?
3. Assuming that it is a bad valve, what's the general opinion on
hardened valve seats, etc. for running unleaded gas? I currently use a
lead substitute with premium unleaded. Maybe this is all somehow related?
4. Any other advice regarding things I should plan on doing while the
head is off and the snow is deep on the ground?
Thanks in advance for any experience/guidance you can provide. I
took apart a few Sunbeam engines in my youth, but am old enough to know
that I didn't know enough to know.
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Dean Mericas
1965 TR4 (CT37089L)
dmericas@limno.com
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