1275 Piston markings

[RussLCV]

I have just taken the head of a replacement 1275 Marina engine that I acquired recently and its seems in good condition, no scoring or lips in the bores and the pistons only needed a wipe over to reveal the following markings

M 2210 X 7

and the letter B is stamped larger on the opposite side..............

Does this mean its been rebuilt and is non standard, I have yet to remove the sump and the big end and main caps to see bearings. I always thought A on the piston head meant it was standard to what does B mean?

Thanks

Russ

[MarkyB]

The B is just the piston grade or size that fitted best when the engine was built.
+10 or + 20 would suggest an oversize piston so I think yours is original.