David Boreham adds to the discussion about unleaded gas:
>
>I should also say that Bill Sohl may be partially correct about Triumphs as
>many of the later models shipped to the US were fitted with stellite valve
>seats. However, the Triumphs in the rest of the world, as well as older models
>certainly can not be run on unleaded.
>
David is on track about the later Triumphs, but what I found most
significant was the complete lack of negative replies (that is
stories from owners that did see a problem) even from the
owners of pre-1970 Triumphs. Of the Vintage Triumph Register's
membership, over 1/2 own pre-70 cars: TR-2 through TR-4A,
early Spitfire, etc. and yet no one reported any noticable
problem AND several mentioned they had ALWAYS used unleaded
fuel (A premium gasoline brand AMOCO, has always been
unleaded, even in the 1950s and 1960s).
This type of "tell me your problem survey" that we conducted is
far from scientific, so I think it is correct to not take a
conclusive opinion from it, still with the large base of
membership, I would have expected some problems to be
reported, even if the problem wasn't related to unleaded fuel
as the cause.
There is, for the USA, one other possible explanation that does
seem plausable. As David reports, the findings of the Rover
testing indicated accelerated wear above 3800 rpm. For
most Triumphs, and in particular the TR series, that represents
a speed in excess of 70mph. As American readers of this list can
attest, the highest legal speed limit anywhere in the US is
65 mph (about 108 kph). Given then, that few US Triumphs ever
are run for extended periods at or above 3800 rpm, this may
explain the total lack of reported valve seat wear problems.
In the report David mentions, it would be interesting to
learn the duration of the engine speeds tested in
the above 3800 rpm range. For example, what was the
equivalent miles (or how long in hours, etc) was the
engine operated above 3800rpm to produce a noticably
accelerated valve seat wear condition?
Lastly, as a comparative point of reference, what
leaded gas is available in the US now contains less
than 0.1 gram per gallon (I think that equates to
about 0.025 gram per litre) so the point made in David's
posting about the futility of mixing leaded regular with
unleaded premium is also true in the USA.
Bill Sohl
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