It is mandatory that the block must be cleaned before it can be inspected; this is useful. Clean the steel structure and make sure to observe the presence of cracks, rust or corrosion on the structure and also examine the threaded holes for stripped threads. It is recommended to take the block to an automotive machine shop that is capable of doing core tests for concealed cracks on it. In the event that there is formation of defects, then the block should be repaired or replace depending on the extent of the defect. Examine for scuffing / scoring, by taking off the cylinder head and using a micrometer, measure the diameter across the top, under the ridge, at the centre and at the bottom of the bores parallel to the crankshaft axis. These measurements should be taken with the block not clamped on an engine stand which in turn causes distortion. Select three reference points on a crankshaft's axis and measure each cylinder's diameter at those points and compare the findings. If the above precision measuring tools are not recalled, feeler gauge stock available at auto part dealers can be used to check piston to cylinder clearance. To check clearance, slip in a feeler gauge with the piston located as shown in fig. 37 and with the actual gauge between the piston and cylinder on one of the thrust faces. Normally the piston should move through the cylinder under moderate pressure; if one finds that the piston goes down with ease then it means that there is too much clearance and that means one has to acquire a new piston. Should the piston feel tightly fitted at the lower end and float at the upper end, then the cylinder bore is considered tapered, while if tight areas are felt while threading the piston/feeler gauge then the cylinder bore is out of round. Perform this process to the other pistons and cylinders that are still unfixed. If, however, the cylinder walls are excessively worn or scuffed, scored, out-of-round or tapered beyond limits, take the engine block to an automotive machine shop and have it rebored and honed, which will require the use of oversize pistons and rings. The block deck should also be checked for distortion using a precision straight edge and a feeler gauge laying the straightedge diagonally on the block. If the cylinders are intact, and one can achieve the piston-to-cylinder clearances, rebore is not required, and honing will suffice.