Just Purchased Virgin 340 Short - What to do with Pistons

cudaracer said

CC's are 65, and the piston are in the bore by 0.07"

Can anyone calculate my CR, assuming deck height is typical

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Mmmmm... you deck height is nowhere near to typical for the early high compression pistons; those stick .018" nominal out of the bores. If they are truly .070" down in the bore at TDC, then IDK what they are; they may be the later low compression 340 factory pistons, but I did not think they were down in the hole that much. The Silvolite 1267 mid-compression replacements don't sit low like that.

So is this 'in the bore by .07" ' for real or did you mean .007" or ???? Do the pistons have 2 or 4 eyebrows? What actual heads do you have?

If you were to put in newer Icon or KB or other newer pistons, you would save considerable weight. The Icon's have a light ring pack. But not sure any of that is of value to you for your use. And the crank would need re-balanced as noted.

Of course we know nothing about the condition of the present pistons, bores, rings, ring grooves. So it is a guess as to what it will do.