When working with Plastigage, three precautions should be taken, Before testing, make sure that all the oil and grease have been removed from the
Crankshaft and bearing surfaces, do not rotate the crankshaft whilst it has the Plastigage in position, and, when removing the Plastigage after the testing process, be very careful not to harm the crankshaft or the bearing surfaces; this can be done via wiping off the Plastigage with a fingernail or a blunt wood stick rather All major and big-end bearings should be checked for clearance when an engine is being overhauled, a procedure which applies whether new or reconditioned bearings are being fitted. First, it is advisable to fit in the main bearings and caps into the engine block after which you have to clean the crankshaft and the bearing portions with oil, grime, and other interferences. Take a strip of Plastigage and fit it along the extent of each of the main bearing journals, then fasten and snug each of the main bearing caps into position in accordance with the torque specifications and in such a way that the arrow on the cap points towards the front part of the engine. Following this tighten all bearing caps and then withdraw them with a view of measuring the flattened width of the Plastigage strip using the scale present on the Plastigage envelope to determine the bearing clearance. To find out if the cylinder bores are out of round, unbolt the Plastigage gently, turn the crankshaft 90 deg and then measure the clearances again using Plastigage the values with the first measurements to gauge for eccentricity. For connecting rod bearing clearance, assembled each
Piston/rod assembly as well as using the Plastigage as mentioned earlier and also for connecting rod side clearance. If the bearings are within tolerances they may be installed as described above, if not they must be replaced by correct size bearings and where upper and lower bearings are affected they must be replaced together.