Oh, Dear, I have to disagree with someone again.....!
John, I'm afraid unleaded fuel does, indeed, contribute to burned valves.
You're right in that improper adjustment or a lean mixture can also figure
in the equation, but unleaded fuel used in a head which has not been fitted
with hardened seats will often result in valve seat recession and burned
It's most important that, any time a cylinder head is off for a valve job,
the machine shop doing the work should install hardened exhaust valve seats
if that has not already been done. Fitting stellite-faced exhaust valves is
further protection against future valve-burning problems.
British Sportscar Center
From: Susan and John Roper <firstname.lastname@example.org>
To: AlexB72 <AlexB72@aol.com>
Cc: email@example.com <firstname.lastname@example.org>
Date: Sunday, March 22, 1998 3:15 PM
Subject: Re: Cyl Head
>> Hi All,
>> I think it's time to rebuild my cylinder head (burnt #4 exhaust valve),
>> was wondering what can be done during the process to increase performance
>> other than milling the head. (1974 MGB 18V engine).
>> Also, what causes valves to "burn", aside from unleaded fuel?
>> Thanks listers,
>> Alex Baroiant
>Unleaded fuel does not cause burned valves. Most probable causes are
>improper valve adjustment and/or lean mixture. John