anomoly

[richard bies <bies@domain.elided>]

Have mentioned a few of the gotchas in switching engines from the '81 to
the '84 GTV6.  Probably no-one noticed.....

I did the switch because the engine became very rough and prone to
back-fire.  Checking compression on #6 (which I suspected), a big zero --
not even a slight pulse as the piston moved -- mechanical de-tensioner;
it has slipped; presumably it slipped again, too far.. So I started
looking for an intake valve and the gead-gasket for that side.  But the
word seems to be that it can be very difficult to remove one head with the
engine in place.  So before pulling the head (and hopeing the piston was
not holed) it seemed prudent to check the other bank.  Zero also on #2.
Both banks have problems -- so I decide to switch a good-running engine
in, and address the problem with engine out; no time pressure (oddly,
only two valves seem to be affected??).  (They go <in> easily -- but you
have to take the whole damned car apart to get the engine <out>....)
Switch completed -- runs good -- now time to see what's with the other
engine, now out.

Clearance on both #2 and #6 intakes had gone to zero -- presumably these
valves are badly burned/bent and stretched.  The heads come-off readily --
but I don't see what I expect to see -- no holes in the pistons (although
#2 valve [only] has clearly been hitting the piston) -- both valves look
fine.  Someone has just had a valve seat facture -- no, the seats are
fine.  How can compression be zero?  Ah -- those valves stand higher from
the chamber than any others -- how can that be?

I recall seeing semi-circle traces on the ends of valve stems thirty-five
years ago in the Giulietta Veloce engine -- the little shims somehow get
displaced (presumably the stems/guides got stickey, or valve-float @ over 
7 grand had something to do with it -- with the stem moving, the shims
can't get away).

Yup.  The same semi-circles.  The stems are not stickey -- how?  The
rev-limiter is under seven, and at that it's the <exhaust> which float
around 7.4.  But both chambers have had something bouncing around inside
(no-longer to be found) -- did it bounce between valve and seat, releasing
tension on the shim and allowing it to get off, then in the subsequent
backfires, get blown back into the plenum, falling into the other cylinder
and doing the same thing?  (Something clearly spent a lot more time in #6
than in #2.)  Wierd happenstance -- seemingly had nothing to do with the
de-tensioner.  This engine is jinxed -- something had wiped the timing
sector casting off the front of the engine,  presumably being what caused
the timing to jump-off on the Turnpike a couple years ago.  Also a wierd
happenstance.  Anyone a better theory?

Don't drop things down the spark-plug holes, or let things get into the
intake, anyway...

r.m.bies

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