Chevy, Gmc, S10 Blazer, Jimmy, adjust, check, timing step by step guide with full pictures:
Note: It is imperative that the procedures included on the Vehicle Emissions Control Information label be followed when adjusting the ignition timing, The label will include all information concerning preliminary steps to be performed before adjusting the timing, as well as the timing specifications,
1: Locate the VECI label under the hood and read through and perform all preliminary instructions concerning ignition timing,
2: Locate the timing mark pointer plate located beside the crankshaft pulley, The 0 mark represents top dead center (TDC), The pointer plate will be marked in either one or two-degree increments and should have the
proper timing mark for your particular engine noted. If not, count back from the 0 mark the
correct number of degrees BTOC, as noted on the VECI label, and mark the plate,
of pulley and mark it with chalk or a dab of paint so it will be visible under the timing light
4: With the ignition off, connect the pickup lead of the timing light to the number one spark plug wire (see illustration). Do not pierce the wire or attempt to insert a wire between the boot and the wire. Connect the timing light power leads according to the manufacturer's instructions. Note: Some engines incorporate a magnetic timing probe hole for use with special electronic timing equipment. Consult the manufacturer's instructions for proper use of this equipment.
5: Start the engine, aim the timing light at the timing mark by the crankshaft pulley and note which timing mark the notch on the pulley is lining up with (see illustration).
6: If the notch is not lining up with the correct mark, loosen the distributor hold-down bolt and rotate the distributor until the notch is lined up with the correct timing mark.
7: Retighten the hold-down bolt and recheck the timing.
8: Turn off the engine and disconnect the. timing light Reconnect the number one spark plug wire, if removed.
Chevy, Gmc, S10 Blazer, Jimmy, adjust, check, timing