The 1968 Chevrolet Corvette with the 327 cubic-inch small-block V-8 engine has a timing marker attached to the timing cover on the driver's side of the engine. This marker has numbers stamped on it representing degrees of crankshaft rotation before and after top dead center. All Chevrolet small-block engines have timing markers in this location. The harmonic balancer attached to the crankshaft has a groove in it that aligns with the timing marker when a timing light is attached to the engine. It is necessary to understand what the numbers on the timing marker mean in order to properly time your engine.
Park the Corvette on a flat, paved surface and set the parking brake. Place the automatic transmission in Park or the manual transmission in Neutral.
Find the timing marker attached to the timing cover on the driver's side of the engine. It sits directly above the harmonic balancer. The harmonic balancer is the large metal disc that the crankshaft pulley bolts to. The edge of the marker looks something like a piece of a saw blade. It has numbers on the high points that read, "12-8-4-0-4-8." The word "BEFORE" appears above the numbers "12-8-4." The word "AFTER" is above the numbers "4-8" that appear after the "0." These numbers represent degrees of crankshaft rotation "BEFORE" and "AFTER" top dead center. Top dead center refers to when the piston is at the very top of its stroke. The low points on the blade, between the numbers count for 2 degrees of crankshaft rotation. Therefore, the low point between the 12 and the 8 represents 10 degrees before top dead center. The ignition timing for this engine is 4 degrees "BEFORE" top dead center. This means that you want the timing mark on the harmonic balancer to line up with the "4"on the "BEFORE" side of the timing marker when you attach a timing light to the engine.
Use a ratchet socket attached to the bolt in the center of the crankshaft to turn the crankshaft and a clockwise direction. Turn the crankshaft until you see the groove that runs across the top of the harmonic balancer. This groove is what lines up with the timing marker when you attach the timing light to the engine. The timing light will make the groove that just appeared hold its position next to the timing marker. Remember, when a timing light is attached to the engine, the groove should line up with the "4" on the "BEFORE" side of the timing marker.
