Bob,
Regarding spark plugs, it was the early cars that used the hotter
N12Y's, the later ones (and the PI cars) used the colder N9Y's. I agree
it's
counterintuitive based only on compression, but perhaps other factors
were at work making the engines run hotter after 1973 despite the lower
CR?
Anyway, my TR250 owner's manual says N12Y and the Bentley
confirms it for pre-'73 TR6's on page 51.
Best Regards,
Tom Marincic
CD3574L
"Early TR6's (prior to CF1) used N9Y, later cars used he N12Y. I believe
that
the earlier cars with the higher compression engines used a colder plug
(N9y) and the newer cars with lower compression use the N12Y. This has been
the case for my TR6's since new... My Dad owned a '70 and then the '74 that
I have now. The '70 used the N9Y's and the '74 N12Y's...
I think you may have the numbers reversed."
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