[T3] Tight exhaust valves

[Jim Adney]

On 26 Dec 2013 at 7:43, Jacob Adam Schroeder wrote:

> My car ('72 FI Squareback) had been running noticeably hotter lately and
> started leaking a little oil from the valve cover gaskets (probably due to
> excessive heat), so I decided to check my valves while I was replacing the
> valve cover gasket.  It had been ~ 1500 miles since the last time I
> checked/adjusted my valves.  Each of my intake valves was still .006, but
> each of the exhaust valves (on all 4) were tight.  Tight as in practically
> no clearance.

Tight exhaust valves are always a concern, but I gather that these 
may have been rather freshly re-done heads. In that case it is 
POSSIBLE that this was just the seats and valves seating into one 
another. With fresh heads, it's always a good idea to do several 
short-term checks and adjustments before going back to the normal 
6000 mile interval.

With rebuilt heads from anywhere, including MOFOCO, you can't be sure 
of what angle they used when they cut the seats, so there will always 
be some uncertainty about how long they will take to seat properly.

While checking the head stud torque is a reasonable thing to do if 
you're worried that they've come loose, it's never part of a standard 
valve adjustment, and keep in mind that you can only get to half of 
those nuts from under there. If you have head studs that seem to keep 
coming loose, it's most likely that they are pulling out of the case, 
so you have much bigger problems. In general, our head stud torques 
never need to be checked.

And keep in mind that the head stud torque spec given in the manual 
is for the OG 10 mm head studs. If your engine has been rebuilt with 
the later 8 mm studs, you must use a different, SMALLER torque, or 
you'll pull the special inserts out of your new engine. That would 
qualify as a real tragedy. The correct 8 mm spec can be found in the 
Type 1 Bentley, because late beetles got the 8 mm head studs.

The only time I've seen exhaust valves tightening up this quickly, it 
turned out that the OG seat was wearing badly, letting the valve sink 
into it quickly, but there was no way for me to know exactly what was 
happening until I got that head off and disassembled. I've never seen 
a valve that was stretching, but I assume it's possible since VW 
gives length specs to check.

I HAVE seen a valve seat that was actually sinking into the head. 
That's sad, because it destroys the head.

I hope you find that after another adjustment or so, the valves seem 
to be holding their adjustment better.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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