Hi Listers,
A month ago I posted a plea for help about my attempts to restart an
abandoned restoration on my '74 TR6. I had cleaned out the old gas [most of
it] and on the third time I started it there were immediately 4 bent pushrods
and 2 broken rockers. Many listers wrote me helpful and intelligent replies
as to why this could have happened, and I promised to let the list know when I
doped it out.
Nearly everyone's theories were simultaneously correct. The engine had
been rebuilt, but diabolically. I'll get to that in a minute. When I got the
head off there were 3 stuck valves. They had to be drifted out with a wooden
mallet. I took it to my machinist and he said it was bad gas. I cleaned out
all the valve guides with carb cleaner and ground in the seats with compound
to be sure none of the valves were bent or not seating. The valves were used,
but the guides were new. My machinist said the clearances were OK.
The reason there was no tappet noise on the initial startup was that all
the rocker adjuster screws were tightened down to zero. So the valves were
held off their seats, got hot, expanded, and seized.
The reason the engine "rebuilder" did that was the rocker shaft was not
replaced, and it was so worn it made a terrible racket, so he just tightened
it down until all the noise went away! It was so worn that the oil galleries
on the side of the shaft were worn completely away, starving the rockers. And
the cam.
While I had the thing apart, I looked at the tappet buckets and said to
myself, "Self, you really don't want to know". So I didn't take them out to
look at them. As it turned out, I really didn't want to know. When I got
it back together with the right clearances at the rockers, number 11 valve
made noise and the rocker arm wasn't opening the valve far enough. The noise
would disappear if I pressed sideways on the pushrod while it was running. So
I guess that cam lobe is wiped. Next weekend I'll take the engine apart
again.
Thanks to the list I know the proper way to bed in a new cam. Anyone got
a suggestion for a RELIABLE STREET CAM?
Misery loves company,
Larry Brown
Asheville, NC
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