> John,
> Please explain CR's.
I'm not John, but I'll take a shot at it. CR is compression ratio ...
higher compression ratios require higher octane fuel. They also result in
more power output and better fuel mileage, so Standard-Triumph adopted the
approach of lowering the compression ratio for markets where higher octane
fuel was not available. The lower CR also affects the optimum fuel mixture
and spark advance to some extent.
So for example, "low compression" TR4s got a Lucas 40842 dizzy, rather than
the 40795 fitted to the "HC" versions.
> Bearing in mind the altitude variations, not to mention fuel types and
> general road conditions, it may be you'll have to equip yourself with
> varying needle and jet configuations to use in your car depending on
> where
> you happen to be.
That's true, but IMO it would take some really severe variations to make it
worth the effort to change needles. For example our fuel here in California
has been diluted by roughly 10% to produce a leaner mixture (with
accompanying poorer fuel mileage and performance) but we get by well enough
on stock needles (and a few turns on the mixture adjustment). And the CR
won't change unless you alter the internal engine components.
Randall
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