Morris Minor Owners Club

I've aquired a 10ma 1098cc engine and when I stripped it down I noticed the pistons were 30 thou oversized which I can't understand as the Haynes manual says only 20 max is possible ?
Is there a reasonable explanation for this size overbore and is it reliable?

In some ways you have already answered your question in that the engine has already been bored to plus 0.030".
Pistons are available for a plus 0.060" re-bore
https://www.morrisminorspares.com/engin ... -4-p830161

Is a 0.060" re-bore reliable? If the re-bore is done properly it is no less reliable than an engine with a standard bore.
I would ignore what you have read and if necessary re-bore the block in question.

Thanks again Phil.
Should I supply the pistons myself or is there an advantage in the engineering firm supplying them?
(£140 from ESM etc.)

So long as the bores are sized to the pistons it will not matter if you or the engineering firm supply them. Check that the pistons are of a good quality.