Does anyone remember what amount of clearance you were running on old school race pistons...........A mate of mine is rebuilding a G 45 Matchy racer..........Not sure why he wants to run the old type pistons other than he is too stingy to buy something more up to date..........these engines had a 66 mm bore size, and I believe the pistons have a split skirt as well.......... Personally I would leave them on the shelf.........any idea's..........Cheers........ Greg. PS: This engine will most likely be running on methanol fuel.........