cylinder bore markings

[paulbell6]

Hi, having dismantled my Stag engine in 1992 I thought I could remember everything needed for the re build, how wrong was I!
I am trying to refit the pistons and one side of the engine has 4 "g"s stamped on the block the opposite side has no markings at all. I assumed that this side would be "F" but I now find having fitted 6 pistons with new rings and shells (all original sizes) and having inadvertantly mixed the last two assemblies up, that I have one g and one f piston left! I have tried to measure the bores to identify the difference in sizes but I only have a vernier caliper and I can seem to make it read anything I want. I have looked at the tolerances for the bores and the tolerance swing between G and F is 0.02mm which seems very small. Does anybody have any advise on the matter please if only regarding the best device to do the measuring?

[Staggard]

Hi you really need an internal micrometer for the bores and an external for the pistons

[flying farmer]

Easiest way is to fit a piston ring into the unworn bit at the top of the bore. I think the difference between F and G was about half a thou, so the ring gap should be about 1 1/2 thou bigger on the bigger bore
(circumference being 3.142 x diameter)
Neil

[paulbell6]

What an amazingly simple but brilliant way to sort my problem out. They say the simple ideas are always the best. Thank you so much! Paul