BlankHi Tom,
My '67 MGB has 330K miles on it and I've never made any modifications to the
head for unleaded fuel. I bought the car in '79 with 100K miles on it and
have rebuilt 3 engines for it, the first when I first got the car. No removed
head has had excessive valve seat wear and I don't use any additives. Most of
these miles were in California. I know there are listers out there who have
had valve problems with unleaded gas but I just haven't had that experience.
Maybe it's because my car has the low-compression engine or the fact that I
always use a 160 degree thermostat. Or maybe because most of those miles were
with the top down.
That being said, the official modification for unleaded fuel is to have
hardened steel valve seats installed. The stock B head doesn't have separate
valve seats so this involves removing enough metal to put in replacement valve
seats. Once this is done to a head, it can never be undone. That head will
require separate valve seats for the rest of its life. Listers have told
horror stories of these valve seats coming loose and doing serious damage to
the engine. Other listers insist that this never happens if the seats are
installed correctly. If you think about it, hardened steel and the original
head metal are very different and must expand differently with heat.
Since different people have had opposite experiences, how do you know which
experience you'll have? You can't, but my choice is always to pick the option
that has the least potential for irreversible damage. If you don't do
anything for unleaded gas, the worst that can happen is that your valves and
valve seats will wear prematurely and then you'll need to pull the head and
have hardened valve seats installed. If you put valve seats in initially,
you'll never know if you needed to or not and the worst that can happen is
that you'll have to replace the engine. You pays your money and takes your
chances.
Denise Thorpe, troublemaker
Tom said:
I know this has come up many times but not when I'm doing my heads. The '65
head goes to the machine shop next week. I need to know what parts to
replace to allow me to safely burn unleaded fuel.
Thanks,
Tom
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