Pistons standard size or not?

Having ripped the entire car apart just to fix a couple of oil leaks, I thought I might as well renew the piston rings and big end shells whilst I’m at it, since I have the head & sump off.

Thing is, whilst the shells say they’re “std”, the pistons don’t say anything. Am I safe in assuming that, in the absence of “+20” or whatever, they’re going to be standard size as well ?

Thanks.

the original Jaguar items I have seen have a letter, oversize pistons should have a size marking

can you measure them, or apply inside micrometer across the bore?

Thanks, Tony. Yes, I’ve only removed one so far and it does have the letter G, so possibly the originals. Bore wear is barely perceptible, although mileage 74k.

Well, I tried measuring but the readings are different on every bore, so I don’t really think my measuring would be sufficiently reliable to detect a rebore ! Maybe the bores need honing a little first, could be some carbon build-up at the very top.

I have always found it difficult to get consistent readings, but if one persists, with inside & outside bore and T-gauges, writing down each measurement, eventually you should get accurate enough that .020" overbore would be very obvious, someone has to make those measurements

Unless the bores are ridiculously worn you should be able to measure the current size.
Measure longitudinally this will give a better guide of the current size as should be less bore wear.
Pistons were stamped with letters at the factory as they were graded but all were standard some pistons did have STD stamped on them but this was mainly on later engines.

Got that sorted, my machine shop expert said that not only are the pistons standard but they’re also the originals. But the oil control rings have seen better days, he told me, so hopefully new ones will show a significant improvement in consumption.

Thanks for the help as always, guys.