Hello again to you all.
Beginning in early spring, I had put the TR6 back together after a valve
job, and found that while the car ran, a pushrod would occasionally pop
out at odd intervals. I had chalked it up to a tight valve guide (as per
several suggestions from this list) and thought that it had finally worn
in--at one point she had gone for 450 miles of driving without a hitch--
when all of a sudden I lost #5 cylinder for good while on a drive to
work. A quick check showed that not only had #9 pushrod popped out, but
#9 valve was stuck open! I got the car back home, pulled the head off,
and took out all the valves. I discovered several things; 1) the #9
valve had a badly scored stem, not from a rough valve guide, but from
some minor abuse by whoever cleaned the valves up when the valve job
was done at the machine shop; 2) the machine shop had installed the wrong
valve springs, putting in the double spring setup for engines from '73 on
(mine is a '72) which might not have been so bad, except that the shop
apparently failed to order the bottom spacers that fit under the springs
for the double spring setup, which is different from the spacers for the
single spring setup (they do not fit properly on the double spring
setup) so they just left the bottom spacers out; 3) in checking out the
old springs, I found that the whole problem with the car in the first
place before I took it into the machine shop for the valve job was a
single defective intake valve spring which had partially collaped,
accounting for the almost non-existent compression on #6 cylinder that
had occasioned the tear-down in the first place. A careful inspection of
the valves seats showed a surprising amount of pitting, suggesting that
the machine shop hadn't ground the valves at all; they had simply replaced
the valve guides and valve springs. I cleaned up the gouged valve stems
and hand-lapped the valves myself and reassembled the head using the
old springs (I had a spare TR-250 head that I robbed a spring from) and
old spacers. After all this, the car now runs fine.
Moral of the story: check everything twice, both before and after you have
machine shop work done, unless you know the shop very, very well (the one
I used was recommended by a sportscar parts man, I had no reason to think
they were anything other than highly reputable). I was very stupid for
just dropping the head off, expecting the shop to find the correct parts,
etc, picking up the finished(?) product and putting back on the car without
a thought (anything that comes back from a machine shop looks good because
it has been so thoroughly cleaned). I should have inspected that head
with a fine tooth comb before reassembling the engine. In fact, I should
have checked the valve springs myself before I took the thing into the
shop in the first place. I would have easily discovered that the leaking
intake valve had a collapsed spring and would have saved myself about
$250 and endless aggravation, not to mention a second teardown, gasket set,
lost weeks of driving pleasure, etc, etc. It is probably unwise to expect
a typical machine shop to know how to deal with an older engine like this
(the manager said he had never heard of a valve train that didnt have
valve seals; he thought I was crazy). This particular shop probably does
good work on standard, good old american iron. As is often recommended
by contributors to this list, check everything twice; parts, procedures,
and especially, reputations of shops to which you farm out needed work;
check with friends and local clubs for several recommendations before
you commit your dollars and find someone who knows these cars at least as
well as you do (preferably better). Sorry to ramble on, but its been a
long, hot summer.
Gary Morrow
'72 TR6, '68 TR250 (here, there everywhere)
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