Piston Help Please!

[TomLS]

Hi all,
My pistons are marked:
AE 20397 -1, 524 EYN
It appears to have been stamped with a very small center-punch, making it very hard to read, so from what I can find, it's more likely to be:
AE 20397 V1.524 EYN.

I can't find reference to this (or variations on it) anywhere! I was told the engine was bored +60, but I can't confirm these, and due to some stupidity on my part (trying to pull the pistons out the bottom of the block instead of out the top...), I need to replace the rings, as I was forced to snap some out to get the piston back down the hole!

Cheers.

[bmcecosse]

What size engine ? If they were +60, it would normally say so on the pistons. They appear to be Hepolite 1098 pistons - and VERY expensive !! To get the size - measure the bore diameter........

[TomLS]

It's the 1098 (or 1156) I'm rebuilding.
Hepolite pistons? What's special about them (/ what are they)? I just pulled the #1 piston (although incorrectly) and it had these markings on it. Having fully stripped out the crank, I didn't have a spare pair of hands to help me turn the block over and check the other pistons. Although I severely doubt an uneven rebore considering the uniform -0!0 of the crank and big ends.

[bmcecosse]

They seem to be available from USA at a great price. Without fail in my experience the pistons would be marked something like '060' on the top if oversize by 60 thou. But maybe not in this case - measure the bores!!!
http://www.englishparts.com/products/MG ... 20397.html

[TomLS]

I have measured the pistons, and found them to be 65.69mm across. That translates to be in increase in diameter of 43 thou, so I guess it's a +40, not +60!
Will standard piston rings do the job, or should I use the proper Hepolite ones?

Thanks.

[katy]

A google search reveals: http://britishpartsdirect.com/index.php ... uct_id=112

[bmcecosse]

No idea if the ring grooves are same size - you could ask the supplier of the rings what width they are and compare with the ring grooves in your pistons. May be safer to just fit new +40 pistons complete from Bull Motif....... However - interestingly that 1.524 mark on the pistons is exactly = 60 thou........... So indeed I think the pistons ARE +60.....

[TomLS]

I don't know HOW I didn't notice that! Clearly, they are just metrically marked... I'll contact a supplier tomorrow and see if they can find the proper rings.

Cheers Roy!