Hi Ian
Further to Kevin's answer it should be noted that the JP pistons supplied by The LDMCC have a much thicker boss than that of the original cast iron pistons which limits the side play necessary to get the pistons to enter the bores. This was done quite deliberately as it was considered at the time of development of these alloy replacements that a thin boss the same as used originally would be too weak. However. to enable them to be used without interference it is necessary to remove a small amount of metal from the short side of the little end. Due to variation in tolerances between individual engines it is difficult to be precise about the amount to be removed but it should not exceed 1.5mm. In many case 1mm is sufficient. The little end is fairly soft and can be cut with a junior hacksaw. Ensure that no swarf is allowed to enter the engine and the saw cut is kept square and deburred properly. If you are unhappy about this procedure, my personal view is that the piston would not be unduly weakened by removing 1.5mm from the inside of the relevant boss: in fact I know of one member who upon receiving a pair of alloy JP pistons machined the boss internally down to the same thickness as the original cast iron pistons and in spite of dire warnings found no problems. At least he never came back to report any. Chris.
