We've been inundated at Gaydon this year with queries from
owners as to whether they can run their 'leaded' cars on
unleaded.
Certainly, the UK press have gone in turbo-charged mode on
this subject, spreading alarm and despondency wherever and
whenever the opportunity arises.
Broadly the situation is this. Within the UK, exhaust
catalysts became mandatory on April 1, 1989. This meant all
cars sold after that date had to have hardened valve seats
to run this fuel. However, for quite a number of years past,
a firm by the name of BRICO had been supplying manufacturers
with stellite or stellite faced valve seats as a matter of
course - often as a matter of simple product up-grade and
quality improvement. Manufacturers are aware that stellite
is acceptable as a 'hardened' seat, though it seems that
many have either lost their records as to when they started
to use them or haven't felt it worthwhile informing the
production cut-in dates. As so many Triumph users seem to
have had no problems with valve seat recession in much older
cars, it's likely BRICO were supplying these components
long, long before unleaded was even being used in the
States. Of course, many UK motoring journalists have failed
to grasp this important aspect and have appeared to used a
simple rule of thumb that valve seats were 'soft' before
April '89 and 'hard' afterwards. Nothing could be further
from the truth.
All that said, there is evidence that some cars continued to
use 'soft' valve seats until quite recently (prior to April
'89) and this does nothing to clear a somewhat muddied
picture.
Jonmac
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