How to Time a Chevy 305 Engineby Robert Bayly
The small block Chevy 305 engine was introduced in 1976 as a fuel economy engine. It has the small bore of the 265 Chevy engine (3.75 inches) and the long stroke of the 350 Chevy engine (3.48 inches). Many parts are interchangeable between the small block engines, and most maintenance procedures are the same. This includes engine timing.
Warm up then engine then turn it off.
Attach the timing light by clamping the spark plug lead over the number one spark plug wire. The number one wire is the first wire on the front of the driver's side of the engine. Attach the power wires from the timing light to the battery with the black wire clipped to the negative cable and the red wire clipped to the positive cable.
Locate the timing mark plate on the timing cover. It is on the lower driver's side of the engine below the water pump and is marked, "BEFORE-16-12-10-8-4-0-4-8-AFTER." If it is hard to see the numbers, spray it with carburetor cleaner and wipe it off with a rag.
Find the groove in the harmonic balancer. The harmonic balancer is the round disc-like part that the crankshaft pulley bolts to. Its surface is directly below the timing mark plate. If you cannot see the groove, bump the engine over with the starter to turn the crankshaft. When you can see the groove, clean it with carburetor cleaner, wipe it dry with a rag and mark it with white-out so it will be easy to see.
Loosen the distributor hold-down clamp with a 9/16-inch wrench. Loosen it just enough so that you can turn the distributor by hand but not too easily.
Locate the vacuum advance hose on the distributor. Disconnect it then plug it with a small screw.
Set the parking brake. Start the engine and place it in neutral. Turn off any accessories, such as the air conditioning. Aim the timing light at the timing mark plate. As the timing light flashes, you will see the notch in the harmonic balancer hover around the numbers on the timing mark plate. The notch needs to be on the "BEFORE" side of the "0." Turn the distributor, in small increments, until the notch lines up with the "4" on the BEFORE side for a car with California emissions and "8" for non-California emissions.
Tighten down the distributor clamp, being careful not to move the distributor. Recheck the timing alignment with the timing light. Turn off the engine, disconnect the timing light and reconnect the vacuum line to the distributor.
Things You'll Need
- Timing light
- 9/16-inch wrench
- Shop rags
- Spray carburetor cleaner
- Small screw
- Be careful to avoid contact with the engine fan and fan belts. Also take care around the spark plug wires, which can give you a good shock.
Robert Bayly, based in Apple Valley, California, began writing in 2010, his "how to" articles can be found on eHow. With more than 15 years in the auto industry, Bayly has been an auto and diesel mechanic, service writer and parts manager. He received certificates from Pontiac (parts system), Cat Diesel (engine service), Saab and Fiat (parts- warranty system).