Bob,
Bummer! Did, perhaps, you replace the valve guides with silicon bronze
guides? I had this happen over the period of a couple of years after I had
the head rebuilt with stellite valves and silicon bronze guides.
The silicon bronze tends to spall, especially when very hot after running a
while. The valve stem seems to expand and small areas of the guide will
yield up a small shaving causing the valve to stick open.
I have had various opinions, but the most common seems to be to ream the
valve guide a thou or two over the recommended size. This, however, leads to
a bit more oil being sucked down into the cylinder and burned, but does cure
the problem. Other say to use plain old cast iron guides and leave the
clearance as original. I tend to prefer the first.
If you havent replaced the valve guides, check for bent valve stems, overly
worn rockers, or even a slightly bent push rod. Any of these can cause the
valve to be pushed slightly to one side and thus hang up. Also check for a
broken valve spring, excess carbon build up on the valve stems, or dirt or
debris stuck under the valve head.
My bet is that it is one of the above.
Keep up apprised.
Regards,
Lew Palmer
-----Original Message-----
From: BobMGT@aol.com [mailto:BobMGT@aol.com]
Sent: Saturday, September 25, 1999 6:20 PM
To: mgs@autox.team.net
Cc: mg-t@autox.team.net
Subject: Sticky Valve?
Today my TD suddenly started making a terrible tapping racket while at
highway speed. I had to limp home at 20 mph. This has happened twice before
in the last two years. The last two times the noise was much diminished
after
the engine had cooled off, and gradually disappeared altogether with gentle
driving. It sounds like valve noise to me. Is this the symptom of a sticky
valve? If so, is there any quick cure? Should I pull the head and have my
mechanic rebuild it? (It's a long drive to my mechanic, I'd have to use a
trailer to take the whole car.) Thanks in advance for any advice.
Bob Donahue (Still stuck in the '50s)
EMAIL - BOBMGT@AOL.COM
52 MGTD - under DIY restoration NEMGTR #11470
71 MGB - AMGBA #96-12029, NAMGBR #7-3336
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