On Fri, 18 Jul 1997 07:06:30 -0400 Leckstein <bleckstein@monmouth.net>
writes:
>
>I did not use hardened seats on the first or second head as I had been
>warned that they often became dislodged and could destroy the engine.
>
That's the first time I ever heard of that, and I wonder if anyone you
talked to actually experienced this. Maybe it is an urban legend or they
weren't installed correctly to begin with.
>This whole history should generate some discussion of whether or not
>it
>pays to modify the valves etc. for un leaded gas use, as the cure may
>be
>more dangerous then the disease. Maybe this applies only to T types as
>the
>later cars, especially the later B's were built for unleaded and the
>casting procedures for the head may have been modified to accept the
>unleaded valve train.
>
>I would be interested to hear comments.
>
By coincidence, this topic was also covered by Mike Ash, Technical Editor
of MGA! in a tech session today. He says he has a couple of cars that
have done 50k to 60k miles on unleaded gas without hardened valve seats
and hasn't had any noticable difficulties. He hasn't had those heads
off, though, to see if there is any valve recession. He does recommend
the stellite valves, whether or not you get the hardened seats and bronze
guides. Other sources I have heard seem to support Mike's experience. I
would be curious to hear if anyone has actually seen a head whose valves
had receded due to use of unleaded gasoline-- I have yet to hear of
anyone with first hand experience with this supposed phenomenon.
I purchase some of the British enthusiast publications, which seem to
reflect some amount of hysteria over this subject, since they are now
phasing out leaded gas in that country. I think there is more concern
than is warranted, considering the evidence so far.
In any case, I have never heard anyone knowledgeable on this subject
recommend pulling a good head just to put in hardened seats, etc. They
only recommend it be done if you have to do work on the head anyway.
David Littlefield
Houston, TX
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