Borgo piston identification

[Raveydavey]

I have an old 66mm borgo here, not oversize and without that cross. Must admit the cross on the one in the pic looks a bit Heath Robinson

[Adam_Winstone]

The +, ++, 0, - all relate to 66mm standard factory tolerances, not oversizes. If you look on the top of a genuine factory barrel you will also see a similar mark, which told them in the factory what to match as pairs during assembly. These differences are slight, probably more like the grading of pistons for plated barrels, certainly not .2, .4, .8, etc of oversizes.

Adam

[Wack]

Standard 57mm

[Adam_Winstone]

Tom,

When you check out the barrel, the mark should be located on top of the barrel, within the area machined flat for the head gasket face.

Adam

[Adam_Winstone]

Sorry, should have added...

Yes, whilst this is a standard 57 and standard rings would be right for it, if the bore is considerably worn, what you may want to do is try to get hold of some 57.2 or 57.4 rings and gap them to the bore. By this means you can normally get more miles out of a slack bore before you need to have a rebore... not that it will stop any piston slap though.

Adam