[AlfonsoR]

Unless you're very experienced and methodical, I would not lap. The silicon carbide cmpd in particular can be very aggressive if high pressure is applied. The lapping strategy would be light pressure and the same duration across all cylinders so that the same amount of material is removed from each.

Remember that the cam housing still has to mate to the heads and that too has a specification for flatness across the three cylinders.

The best would be to have the case machined so that all cylinders start out at the same height with relation to the crank centerline. Second, each cylinder should be machine finished to the same height. Third, each head is machined to give you a consistent height for the cam housing to fit within a certain spec of flatness across the three cylinders on each side.