The engine must be cold as the checking of the valve clearances should be done only in case where camshaft or other parts related to the valve have been changed or replaced or where excessive noise is heard coming from the valve train area. Loosen the connection of the cable from the negative terminal of the battery, next remove the spark plugs and the valve covers. Loosening the crankshaft pulley centre bolt one can use a socket and a breaker bar to rotate the engine until the camshaft lobes of the cylinder to be checked are positioned away from the tappets. With the feeler gauge, ascertain valve clearance for the valves which have been indicated and ensure they jot down all the readings taken; then compare the observed readings with the standard valve clearance in order to point out those valve clearances which are beyond the standard. Do the same process to all valves to obtain its initial measurement. If any clearance is out of specification, one has to replace the tappet with one of another thickness to correct it and, of course, the camshafts have to be removed in order to be able to deal with the tappets. Sticker the lifters for replacement and the valves that should go together with them using a micrometer to measure the thickness of the head of each lifter to the nearest 0.001 inches. If you'd like to know how thick the new lifter should be so as to achieve the desired valve clearance, then the formula N equal R + (M1-M2) should do it for you, where N is the thickness of the new tappet, R is the thickness of the old tappet, M1 is your measured valve clearance and M2 is the standard valve clearance. Coated lifters are coded on the bottom aspect to express their measurement where a marking of 3.310 denoted thickness of 3.31 mm or 0.13 inch. At last, select the new lifters that should be placed in the specific location, while apply the engine assembly lube on it, and place it into its correct position; replace the camshafts and timing chains back, and check it with the valve clearance.