I have had more experience with British bike cylinder heads than MG's, but
the argument about hardened valve seats rages on amongst the enthusiasts of
these machines also.
In my personal, subjective experience with normal, non-hardened valve seats,
the presence of lead in the fuel had no noticable effect in preventing
valve-seat recession. In fact, few Brit-bike used cylinder heads from the
50's and 60's can be found without the valve seats being seriously pocketed.
I think there are other factors that may be more influential than unleaded
fuel on the longevity of valve seat material.
I have no doubt, for example, that the average Brit Bike was thrashed, in
every sense of the word, much more than the average LBC.
My Triumphs have aluminum cylinder heads with cast-in, cast iron seats,
similar to the material our MG's are cast from. I have a '68 Bonneville that
made it to 1982 with good seats, at which time I restored it. It has a
further 20,000 miles on it, all on unleaded fuel, and at last look this past
season, the seats are still like new. But this bike is one of my pride and
joys, and is never thrashed and always impeccably maintained.
Other heads in my garage with much less use have seats receded past useful
service. The variable seems to be running frequently at redline, (as in
"racing"), extreme cam profiles requiring heavier than stock valve springs
to avoid valve clash and float, poor or no maintenance, or use of cheap
chain-store oil, and lack of proper air filtration.
I suspect Maynard, you drive at less than redline and maintain your car
properly as an enthusiast like you surely must. That is likely why your
"soft" seats still are lookin'good.
On my recent rebuild of my MGB's head, I had hardened seats installed
never-the-less, because a/ they are relatively inexpensive to install,
b/I have fitted a supercharger and a heavy-valve spring cam, and c/ I plan
to thrash the bejeezus out of it at every opportunity because it goes soooo
good.
Be a good boy (girl!) and drive easy and your valve seats will last a long
time.
Pump up the pressure and drive it like a sports car often and you might like
the extra life hardened valve seats bring to your cylinder head.
Happy New Year!
Dave
>From: "mghirsch" <mghirsch@netzero.net>
>Reply-To: "mghirsch" <mghirsch@netzero.net>
>To: <mgs@autox.team.net>
>Subject: Re: Blown Head Gasket
>Date: Mon, 31 Dec 2001 14:01:14 -0600
>
>There is aobut 40000 miles on my car since I rebuilt the engine. I did not
>use hardened valve seats. This spring when I had to do a head gasket, I
>had
>the head and valves checked. There was no problem with either the valves
>or
>the seats.
>
>What has to be understood is that the seats themselves become hardened with
>use. The constant closing of the valves acts like a mini-forge and hardens
>the seat.
>
>While I'm not saying that no one has had a problem, I have not noticed it
>in
>any of my cars, or in the engines I have worked on. If you want to do it
>fine, but I have found more problems with the seats becoming loose than
>with
>valve recession.
>
>Maynard Hirsch
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