Sam,
Your summary seems to profile the difference in early Spitfire 4
cylinder engines and the later (Large Journal) ones. I don't know much
about the GT6 engines, but it would appear that the later ones follow
the same sizing as the Spits. I suspect you have a later GT6 engine,
correct?
Joe
Sam Gentry wrote:
>
> OK... I am confused... I am checking the crankshaft from my 73 GT6 and the
> dimensions that I get are not even close to the numbers in my Bentley. The
> rod journals are right on, but the main bearings are way off. The book
> says 2.001 to 2.0005, but I measure 2.312!!! I have used two micrometers
> and a dial caliper and get the same answer. I have an old crankshaft that
> measures more or less the same (it is fairly worn). Does anyone know the
> correct crank main bearing specs? I don't see how I could be off by 0.311!!
>
> While I am at it... What is the correct bore diameter? The book says
> 2.9405 to 2.9416 in three grades, but pistons no longer seem to be
> available in grades. The book says that the bore can be as much as 0.010
> over, but over what? What is the nominal dimension? Of course,
> 2.9405-2.9416 is only 0.0011 so I guess it does not matter much which
> dimension I use. The middle is 2.941 and that is a number I have seen. My
> bore is about 2.945-2.947 which is within 0.010 of 2.941. It is even
> within 0.010 of the smallest diameter specified.
>
> More while I am at it... If the bore is less than 0.010 oversize does that
> mean that I can use standard rings?
>
> Thanks, Sam
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