What is a Quick Way to Check Valve to Piston Clearance on an Assembled Engine?
Low tension checking springs, Part Number 99881-2, must be used (instead of your normal spring) to mock up your valve train and to check the piston to valve clearance on the engine. Assemble the valve train and verify correct lifter preload or valve lash. By mounting a dial indicator on the cylinder head with the plunger's tip on the valve spring retainer, you can quickly check the clearance.
Hand rotate the engine through a complete cycle (two rotations of the crankshaft), stopping at several points before and after Top Dead Center (T.D.C.) to check the valve clearance. The least amount of clearance will usually occur between 15 degrees before T.D.C. and 15 degrees after T.D.C. This also provides a graphic illustration that gross valve lift does not determine piston to valve clearance, as the piston is fairly far down in the cylinder when maximum valve lift is reached.
By pushing the rocker arm down with your finger, the valve will contact the piston. The amount of movement shown on the dial indicator is the valve clearance at that point of engine rotation. Rotate the crankshaft a few degrees and re-check the clearance. As the piston moves through this area, the dial indicator reading will lessen, then become larger as you rotate the engine past the critical point. The shortest reading you get is the actual valve to piston clearance.
Hand rotate the engine through a complete cycle (two rotations of the crankshaft), stopping at several points before and after Top Dead Center (T.D.C.) to check the valve clearance. The least amount of clearance will usually occur between 15 degrees before T.D.C. and 15 degrees after T.D.C. This also provides a graphic illustration that gross valve lift does not determine piston to valve clearance, as the piston is fairly far down in the cylinder when maximum valve lift is reached.
By pushing the rocker arm down with your finger, the valve will contact the piston. The amount of movement shown on the dial indicator is the valve clearance at that point of engine rotation. Rotate the crankshaft a few degrees and re-check the clearance. As the piston moves through this area, the dial indicator reading will lessen, then become larger as you rotate the engine past the critical point. The shortest reading you get is the actual valve to piston clearance.