The V8 Owners Forum -

Anyone know what "M" stamped into the piston crown signifies, there is also an "M" stencilled onto the area below the hyd tappets underneath the valley gasket.

Perhaps manufactures by Mahle?

They are a well known piston caster / manufacturer

Ian

I can confirm that some pistons do have an M on the crowns even when they were produced by Hepolite.

I rebuilt a 3.9 for a friend with cracked a liner and went down the route of getting the block fitted with top hat liners. The company that fitted the liners (I think ACR) needed to know what marking was on the piston crowns as it decided how the liners were finished. Needless to say his pistons had the M on them.

landrovernuts wrote: '...The company that fitted the liners (I think ACR) needed to know what marking was on the piston crowns as it decided how the liners were finished...'

hmmm must be quite important if it decides how the liners are finished. some digging needed here...