Most people won't have a problem; which is why I always say to see if you
have a problem first. From what I've read, having been run on leaded fuel
in the past tends to leave a protective layer on the seats, which will
usually prevent recession even on unleaded fuel.
But my TR3 was a "barn find", apparently in the middle of quite a bit of
work but effectively abandoned back in the 70s. I don't know that much of
the history, but it might have had a valve job (thereby destroying the
protective layer) and then never been run on leaded fuel. At any rate, it
is the only TR3/A that I've owned, that cared about unleaded. And as I said
before, installing a different head (also unknown history but no sign of
exhaust seats having been changed) solved the problem.
The hardened seats are not expensive. There is some extra machine work to
install them, but it doesn't add very much to the overall cost of a valve
job. I don't recall the delta for the seats, but the entire job, including
new guides, valves, exhaust seats and springs was under $500.
BTW, using 100LL in a car on the street is illegal. I'm told that most
airports will refuse to dispense it into a can, unless you can prove you own
an aircraft that uses it. They can also be held liable if you get caught
putting it in your car; so there's no way they are going to pump it in
directly.
I forget the numbers offhand, but even though "LL" stands for "low lead",
100LL contains far more lead then even the old leaded premium. So it
wouldn't take a lot, maybe only a gallon or two, to treat a tankful of
regular. But even carrying a few ounces of RLS around is a PITA. I'm
really not interested in carrying around a couple gallons of avgas just so I
can fill my tank when it runs low.
Those Amazon prices are ridiculously high (something I've noticed more and
more with third party sellers on Amazon). Shop around, I'm sure you can
find it cheaper than that. For example, Summit only wants $12/bottle, and
shipping is free on orders over $100.
-- Randall
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