> I am the proud new owner of a 71 GT6 MKIII and have a basic
> question. I was informed by the previous owner that I should add
> a lead additive to the fuel. How importnant is this and what
> happens if it is not added? Are there long term effects? Thanks
> in advance.
Cameron, just to clarify (hopefully) other's comments : Some older engines
may suffer what's known as "valve seat recession" when run on unleaded
gasoline. This seems to be primarily true of engines that are run at full
output for long periods of time, like trucks and race cars. "Lead
additives" (which do not contain lead and are more accurately known as "lead
substitutes") are intended to combat this problem.
However, many (most ?) engines do not suffer valve seat recession even when
run on unleaded, and there is some evidence that Triumph was already
hardening valve seats by 1971 in anticipation of the elimination of lead.
Previous running on leaded fuel may also harden the seats enough that
switching to unleaded will not cause VSR. Also, you'll know fairly quickly
(and before much damage occurs) if your engine is suffering from VSR,
because the valve clearances on the exhaust valves will be too small when
you check them as a normal part of a tune-up.
So my suggestion is to save your money for a valve job (hardened valve seats
are both the cure and real preventative for VSR) at least until you know if
it's a problem for your engine and your driving. Odds are very good that
you'll have the money for a valve job long before you need one, and won't
have to mess with carrying messy, smelly (and toxic) chemicals around to add
to each tank of gas.
Randall
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