Lawrie Alexander wrote:
>
> 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
> valves.
>
> 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.
>
> Lawrie
> British Sportscar Center
>
> -----Original Message-----
> From: Susan and John Roper <vscjohn@iamerica.net>
> To: AlexB72 <AlexB72@aol.com>
> Cc: mgs@autox.team.net <mgs@autox.team.net>
> Date: Sunday, March 22, 1998 3:15 PM
> Subject: Re: Cyl Head
>
> >AlexB72 wrote:
> >>
> >> Hi All,
> >>
> >> I think it's time to rebuild my cylinder head (burnt #4 exhaust valve),
> and I
> >> 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
> >> 74MGB
> >
> >Unleaded fuel does not cause burned valves. Most probable causes are
> >improper valve adjustment and/or lean mixture. John
> >
Lawrie, I don't think we disagree. My second post did not make the net
, some problem? Unleaded fuel used in an engine with the softer seats
intended for leaded fuel may cause valve recession which, if it occurs
will result in tight valve clearances and the burned valves that often
result from tignt clearances, but the cause is still failure to keep the
valve clearances where they belong. After much wringing of hands and
knashing of teeth, most find that pre-unleaded engines subjected to
occasional and less than heavy use suffer little recession. An engine
used for daily transport or by a heavy-footed user is the exception.
John.
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