The UK finally banished leaded fuel availability in 1999. In the run-up to that
event, there was a
lot of panic (fuelled (no pun) by the Press) that unleaded fuel was unsuitable
for classic car
engines as a whole. This has proved to be bunk with cars that had cast-iron
heads. At that time I
was working for BMIHT and did a lot of research for enthusiasts prior to
releasing a publication on
what they were supposed to do. The findings were as follows:
1. Cast iron head engines - even without hardened exhaust valve seats, create
what is basically
known as 'lead memory' - in other words, lead is absorbed into the cast iron
rather like a sponge.
2. There really is no need to panic and fit hardened seats as all Triumph
engines have proved to be
exceptionally tolerant of lead-free fuel without hardened seats.
3. All that is needed is slight retarding of the ignition.
Of course, if you want to use an additive, potassium is widely held to be the
most suitable as a
lead replacement. To the best of my knowledge, the factory did not ever fit
hardened seats to cars
for North America, even though unleaded fuel was available there long before it
was in Europe and
the UK. With this in view, surely the factory would have been concerned about
valve seat life where
unleaded was widely available and IF it had felt hardened seats were desirable,
I'm sure it would
have fitted them for all markets and not just North America. My 2.5PI now has
over 250,000 miles on
the original head. It has certainly had new valve guides in my ownership but I
thought I'd wait to
see how it coped on unleaded without an additive. At 10,000 miles of hard
driving, no sign of valve
seat recession and I think it actually performs better on unleaded than it did
on leaded!
My 2 cents worth
Jonmac
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