I rebuilt my motor this past spring. I put about 7000 hard miles on it
this summer (four months of touring the southwest) with no real
problems.
About two weeks ago I started hearing a "tappet" noise and promptly
pulled the cover to discover the set screw on the rocker shaft had
gone to it's grave and was nowhere in sight. I replaced the set screw,
checked for wear and reset the valves (they were all within .002". No
joy same sound of a single valve banging away.
Ran a compression check and no sign of trouble, readings between 164
and 172 psi. Pulled the dizzy and checked advance springs and weights,
all good. Retorqued the intake and exaust manifolds, no change.
Reduced ignition timing and got a very slight improvement.
The sound is coming from the valve cover between the number three and
number five cylinders. The pattern is at half engine speed and a
single sound very much like a valve out of adjustment. The sound is
most pronounced at 1200 to 1400 rpm and almost non-existant at 2800
rpm although it becomes obvious again above 3300 rpm. The sound
becomes less as the engine warms but is always present.
I am beginning to suspect a lifter is sticking. I did not replace the
cam and lifters when I rebuilt the motor as they speced fine. It seems
to me if a valve was sticking it would have shown up before and would
be more likely to stick when it was hot not when cold.
I'm stumped. Anybody have an idea what this may be? I hate to start
tearing down the engine and replacing expensive parts just to see if
it improves.
By the way this is my only transpotation and has been since 1989.
That's right I'm one of those hardcore "drive it like it's
transportation" people. This has been a very reliable car for over 25
years. Please help.
Barry
'71 signal red GT6
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