Let me start by introducing myself. My name is Glenn, and I live
in San Antonio Texas. I own several TR7's, one for 8 years that is my
daily driver, and a couple others which I'm in the process of fixing up.
I've been a lover of LBCs ever since I was a kid, and my oldest brother
bought a band new 1967 MG. I just signed up onto the Triumph list last
week, apparently not the best weekend to start. But overall I'm enjoying
hearing some of the advice and tech talk and am glad I've signed on. I
am a bit jealous about the good weather all over the country. Here in
south Texas it has been raining for a steady week.
I agree with the comment that the actual numbers on a compression
test are not as critical as the differences between the readings. As you
can tell from the responses there is no absolute number which one call
declare the engine good or bad. There is many different factors that can
make the overall reading all high or all low, from barometric pressure,
humidity, timing, temperature(both outdoor and engine). When I lived in
Wyoming, at 7000 ft altitude, I was lucky to get readings above 110. Now
that I'm down closer to sea level my pressure readings are considerably
higher. The main purpose of a compression test is to find a cylinder(or
cylinders) with excessive wear. Normally one can consider the cylinder
with the highest reading to be the most efficient cylinder. The cylinder
with the lowest reading is the least efficient. If the difference
between the two cylinders is greater then 15%, then there is a problem to
investigate. If two cylinders side-by-side are low, that is a good
indication of a blown head gasket. If one cylinder is low, then a squirt
of oil, as describe by another reader will lead you to the problem. If
the compression of the low cylinder increases with the squirt of oil,
then the rings are leaking, if the readings stay low, then a leaky valve.
The concept of pressurizing the cylinder sounds interesting.
I'll have to check that out. My father used to pressurize the cylinders
in the fashion described to change to valve seals without removing the
head (the pressure keeps the valves from falling in).
I've seen a lot of references to history books and commission
numbers this weekend. One thing I've learned over the past years is to
not put much faith into BLC record keeping. I have a TR7 which the
title say 1976, the emission sticker says 1976, and the exhaust design is
typical of 1976, but "the books" indicate that the commission number is
1977 model. I've also know of a 69 TR6 which came from the factory with
TR5 door panels, always a problem in concourse competition since it
doesn't look original, and several cars with commission numbers or
paint codes that don't exist according to "the books".
Again, I look forward to hearing all of your experiences and tech
tips. (and No, I'm not a doctor, I am one of the common folk who can
barley afford to keep my car on the road, and love every minute of it).
Glenn Haslem
2 1976 TR7, 1979 TR7
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