The piston must fit properly into its corresponding connecting rod and this is most efficiently done by special tools with help from an arbor press if available and by a professional. New piston rings should be of the same size as the piston that is to be employed for the rebuilt engine, and the process of setting them offers key to constructed engine's process. Before putting the piston rings, one must take some measurements on the ring end gap, which has to be done for each piston ring and for all the entire set of piston rings that must include a top ring, a second ring and a three-piece oil control ring. Screw one top ring into the bore of the cylinder so that it is perpendicular to the cylinder wall then, when another top ring has been fitted, use a feeler gauge to measure the gap between the two ends of the ring. If the gap is lacking, remove the ring and put a new top ring in its stead then check all top rings whereby by use of a fine file trued to size. As with the second rings and the oil control rings measure the end gap of each second In the same way. Roll a piston ring over the groove of the corresponding piston to feel any bind; if rings are distorted, replace them. If available use a piston ring expander or small lengths of tin to align the ring gap on the piston rings to the appropriate grooves when fitting the rings. Loosen and install the bottom oil ring spacer and its components and check that they float in the groove and do the same for all the pistons. The piston rings are to be correctly fitted and properly cleared in their respective grooves and the fitting should be checked using a blade feeler gauge and correction if any should be done.