[T3] ? Mystery of the Clacking Valves ?

[David Yaghoubian <goob@roadrunner.com>]

<x-flowed>If you've got one of those Sherlock Holmes pipes, spark it up... :)

Keeping this as succinct as possible to start, my super clean, 
perfectly running 1776 (@~35K miles) developed a bad pushrod tube 
leak in the outside tube for the #3 cyl last week. It never skipped a 
beat that I noticed, but was spraying oil, so I had to get it fixed 
pronto since it's my daily driver. Not having time to do the job 
myself I took it to my local shop... highly trusted folks who have 
been working on VWs since the mid-70s and who have routinely done me 
and my square right over the past decade. What they found was that 
the pushrod in the leaking tube was bowed/bent (!) and had been 
rubbing on the inside of the tube, causing the leak. They pulled the 
engine and removed the head to see if there was any damage to the 
valve or seat that might have caused the pushrod to bend, but the 
head looked perfect. So they put the head back on with a new tube to 
replace the leaking one, installed a new set of pushrods and lash 
caps all around, adjusted all valves, drove it around, then adjusted 
the valves once again when it was cold. The mystery of the bent #3 
pushrod remained... I have it here as a souvenir to ponder.

Soooo... I drive home, and then to work and back the next day (~30 
miles total) noticing that the idle keeps creeping up...eventually to 
around 1500rpm at idle. The valves sounded loud as hell when I went 
back to check the engine, and I could tell something was way off due 
to abnormal fumes/smell.  So I waited until the next morning until 
they were dead cold, and went to do a valve adjustment. I was shocked 
to find all of the valves more out of adjustment than I had ever seen 
on a VW engine.... I'm talking about  1/8/ to1/4 in. gaps...I don't 
have a gauge in the kit to span that canyon!!! The rocker arms were 
tight, and nothing looked broken/missing anywhere. So I called up the 
shop owner, who was about as surprised as I was to hear this, and 
didn't really have an explanation beyond that the rods had possibly 
shrunk or reseated somehow, but basically concluded he wasn't sure 
how that could happen. We decided I would finish doing the 
adjustment, and see what happened after some more driving.

Sooooooo.... I did the valve adjustment all around (.004 as usual) 
and did another round trip to work on the freeway (~20 miles total). 
The next morning I check the valves dead cold, and am amazed to find 
that after my easy freeway commute they were all way out of 
adjustment again. The outside #1 valve was so far out of adjustment I 
had to use up almost all of the remaining thread on the adjustment 
screw to get it back to .004. The other valves weren't nearly as bad 
as this one, but were all at around .013, which is still insanely 
loose... after only a 20 mile drive! I called up the shop with the 
news and they said to definitely bring it back in asap so they could 
determine what the heck was going on.

Which brings us to today. They pulled the new rods out (an EMPI set) 
and nothing looked bent/broken or out of the normal. They replaced 
the EMPI set with a new set of Scat rods, which rumor has it are 
superior steel than the EMPIs. (?) Before putting the new Scat rods 
in they used a tiny camera to look at the lifters, and aside from 
what was described as a stripe of what looked like rust on that 
outside #3 cyl, nothing looked out of the ordinary, and the engine 
oil is still clean-clean. They test drove it on the freeway today, 
and are going to do the valves again before I pick it up tomorrow 
morning to give it another shot.

Hence, the mystery of the clacking valves. Does anyone have any 
explanation(s) for how the above could transpire? To start, I am 
stumped as to how the #3 rod was originally bent/bowed. More bizarre 
is the radical change in valve clearance/adjustment on all cyls, and 
especially the #1, which used up a full adjustment screw's worth of 
thread in less than 50 miles. Aside from the cam lobe getting ground 
down severely (which one would expect to see in the oil, no?) I can't 
for the life of me understand the physics/geometry behind this. Where 
did that ~1/2 inch on #1 disappear to?! Ultimately I'm going to pick 
it up tomorrow, drive it, and check the valves again (and again) but 
since this engine has thus far been 110% reliable and never seen any 
abuse/trauma I'm just very curious, and more than a bit concerned.

Thanks to any and all who might be able to sleuth this and shed light!

Dave Y.
68 Square 

_______________________________________________
VWType3.Org mailing list - type3@vwtype3.org
http://lists.vwtype3.org/listinfo.cgi/type3-vwtype3.org
Contact gregm@vwtype3.org if you need help with the list.
</x-flowed>