Morris Minor Owners Club

So.......was the old piston oval?
Hmmm........pistons are oval anyway, so was it excessively oval?

Scott......Didnt check it mate ! Spoke to lots of guys @rally they reckoned it shouldnt have happened ,&revs should be ok @5000 plus . All agreed that what with all the messing with guarantee arguments etc ,it was prob. worth paying the money to fix it myself ,also that it could have been just one 'rogue'piston . I've now got this idea in my head that I need a replacement engine ,hence my other postings !!!

Hmmm........pistons are oval anyway

Are you sure?? All the ones I have come across are not oval. Or do you mean they are oval after being used for a while??

Spoke to lots of guys @rally they reckoned it shouldnt have happened ,&revs should be ok @5000 plus .

Yes, 5000 + should be fine (as long as you don't go much +!!).

Unfinished (fresh from the cast) pistons need to be cam ground to size as the areas of different thickness in the piston expand at different rates. There's only a few thou in it, but they are oval to a certain degree.

Unfinished sidevalve pistons seem quite common here (old stock) but there's not too many machine shops who can cam grind them. I had some done a few years ago & seemed to have found the last person in Sydney who was able to do it (& he was retired, but luckily kept his old w/shop gear).

As Cam says, 5000 rpm should be fine. Pistons aren't renown for being the weak point in "A" Series engines .