Timing Components: Testing and Inspection

CHECKING VALVE TIMING





Since the valve timing mark on the back of the cam drive pulley is oriented to the TDC firing point for cylinder # 1, valve timing can be checked easily on a running engine with a timing light as long as ignition timing is correct.

The camshaft runs at 1/2 crankshaft speed and the ignition timing point is 3° after TDC, so the timing light will flash 1 1/2° away from the cam timing mark. Each tooth on the cam drive pulley changes valve timing about 16° so the 1 1/2° error makes no difference.

Run engine at idle.
Make sure ignition timing is correct.
Shine timing light onto back of camshaft drive pulley.
Valve timing mark should be aligned with edge of valve cover gasket.

If valve timing is incorrect:
Turn engine and align ignition timing mark on flywheel to cylinder # 1 firing point.
Remove alternator belt and cam belt cover.
Loosen belt tensioner and remove belt from cam drive pulley:
Make sure drive belt remains seated around crankshaft and intermediate shaft drive pulleys.
Turn cam drive pulley and align mark with edge of valve cover gasket.
Re-install drive belt and re-set tension.
Re-install drive belt cover and V-belt.
Re-check ignition timing and valve timing.