The piston/connecting rod assemblies must needed to be cleansed, and the initial piston rings have to be taken off from the pistons and additionally new piston rings have to be incorporated at the time of reassembling. A piston ring expander tool is to be used to ease out the rings without scratching the pistons. Carbon deposits have to be removed manually with a wire brush or fine emery paper from the top of the piston down as far as the rings; use of electric wire brush erodes the piston's material. Dirty deposits made of carbon can be wiped out by using a piston ring groove cleaning tool or a fragment of an old piston ring paying attention to possible damaging of the grooves. After that the piston/rod assemblies need to be cleaned with solvent and if possible the piston/rod should be blow dried with compressed air. If the pistons and cylinder walls are not worn out or damaged keen and the engine block is not rebored new pistons may not be necessary as they are usually over sized but new piston rings should always be fit in a rebuild. Every piston should be for signs such as cracks, scoring, scuffing, hoop cracks, holes and burned areas as these suggest that the piston has overheated or there are abnormal combustions and thus a thorough check of the cooling and lubrication systems should be made. Electrolytic (non uniform) corrosion shows up in the form of small pits around the openings which points towards the possibility of coolant leakage and this must be rectified before rebuilding the engine as it may occur again. Side clearance of the piston rings should be done using feeler gauge at several positions on each groove and the right ring should be used for the right groove; in case the clearance is above the prescribed limit, then new pistons will be needed. Piston to bore clearance must be checked by measuring the bore diameter and piston diameter and checking whether they are correctly matched and calculating the clearance by subtracting the piston diameter from the bore diameter; if the results show too much clearance it means that the bore requires rebore and new pistons and rings must be fitted. Piston-to-rod clearance has to be checked by turning the piston and the rod in opposite directions; if there is significant end-play, often felt or seen, some or all of which may be removed at an automotive machine shop. In case pistons require removal from connecting rods they should be taken for assessment for bend and twist to a machine shop. Connecting Rods should be checked for crack and damage by removing the rod cap to clean the bearing surface, looking for nicks or scratches, old bearings should be replaced new ones installed, and caps tightened with finger tightening if rebuilding because of connecting rod knock then new rods should also be fitted.