[TR] (no subject)

[Randall]

> What causes an exhaust 
> valve to get stuck open? How do I fix it? This engine rebuild 
> is relatively recent.


Most likely, there is not enough clearance in the valve guide for the valve
stem.

Valve guides are normally replaced as part of an engine rebuild.  The guides
are deliberately made a small amount oversize, so they crush a bit during
the installation process and the hole closes up.  This compensates for any
variation in machining the holes in the head.  So, It is important that
after the guide is installed in the head, the opening in the guide is reamed
to the proper size. 

The problem is compounded by the common use of phosphor-bronze valve guides
instead of the stock cast iron ones.  The bronze guides need to be reamed a
bit larger than iron guides do, because bronze expands faster with heat.

It is possible there is some other problem; but the next step is the same :
The cylinder head will have to come off, so you (or a machine shop) can
disassemble that valve, identify and correct the problem.

If the problem is lack of clearance (undersize guide), I would want to check
all the other valves as well.

-- Randall 
56 TR3 TS13571L once and future daily driver
71 Stag LE1473 - awaiting engine rebuild
71-2-3 Stag - awaiting gearbox rebuild