To recap, I'm searching for clues to low compression on my TR6.
I managed to sneak away for a few minutes from the Daimler adventure,
and checked a few things on the TR6. I did not take another
compression reading, as I felt comfortable that what I had seen was
likely to be true. You can bet that another compression reading will
be taken before the breaker bar comes out of the box though...
I pulled the rocker cover, and set #1 at TDC on the compression
stroke. I then checked the orientation of the rockers which revealed
that the cam was correctly positioned with the crank. #11 and #12
valves were exactly even, which is how one locates the correct
orientation of the cam WRT the crank. As I moved the crankshaft
pulley back and forth #11 & #12 valve would move up and down the
instant the crank would move. Humm... both valves must be slightly
open so this particular cam must have some overlap there. The #6
piston is on it's way down on the intake stroke, so the exhaust valve
is just about closed and the intake has begun to open. To me, this is
the correct behavior, according to what I read in the Bently manual.
I was unable to locate a source for a leak down tester, so I'll have
to wait to find one of those. Anyone have a good source for one? I'd
really feel better to find out what's going on before doing anything
drastic.
Someone mentioned stuck valves. I would be surprised, as all the
valve guides were replaced. The shop that rebuilt the head used the
old valve springs and used shims (if needed) to set the seat pressure
back to stock specs. Perhaps my springs are a bit weak. Could weak
springs cause low cylinder pressures? I would think that weak springs
would only effect the higher RPM running range, where the valves could
possible "float". Besides, the car runs great on the highway and at
higher RPMs.
It was also mentioned if I checked the ring gap in the cylinder during
the rebuild. Uh, no, I didn't. The reason was that the pistons were
shipped to me with the rings already installed, and I didn't want to
take the chance of breaking the ring while removing them. I wish I
had done that now. The leak down tester would probably answer this
question though...
I don't think I'll have much time till after Thanksgiving to further
test this little mystery. The Daimler has a yearning to be put back
on the road before thursday, so we'll be putting in the late hours to
get that baby back to it's home port.
Thanks for all the suggestions so far. Larry (Snyder), let me know
what you find in your #6, maybe it'll help me figure mine out!
Cheers,
-Scotty "what goes up, must come down" Paisley
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