Initial distributor timing on the Chevrolet 350ci engine is easily set by do-it-yourself car maintenance enthusiasts using just a few tools and an inductive timing light and should take only a few minutes. The amount of ignition advance will depend on the engine version and model of auto, but is generally set between 8 and 12 degrees before top-dead-center (BTDC). Contact a local Chevy dealership parts department or a parts store for the correct setting.
Secure the car so that it cannot move while running. Engage the parking brake or place chock blocks in front of and behind a wheel to prevent the car from accidentally moving. Bring the car to operating temperature. With the car in park (or neutral), remove the air intake filter assembly. Disconnect any vacuum lines the assembly may be attached to and plug them if necessary. Disconnect the vacuum hose attached to the distributor vacuum advance and plug it. Turn the car off.
Attach the power leads of the timing light to the battery. The red lead is clamped to the positive terminal of the battery and the black clamp is attached to the negative terminal. The third cable of the timing light--the inductive pickup--is attached around the spark plug lead (wire) of the number-one cylinder (front, driver's side spark plug). Ensure the timing light cables are clear of any moving parts and restart the engine.
Aim the timing light at the marker (timing pointer) on the timing cover adjacent to the harmonic balancer, and activate the strobe (usually with a trigger). The harmonic balancer is a 6- to 8-inch diameter disk attached to the front end of the crankshaft. The flashing strobe of the light will illuminate the timing marks on the balancer to point to the initial advance the distributor is currently set at. If the indication is incorrect, loosen the distributor clamp bolt with the 9/16-inch open-end wrench or distributor wrench just enough so that the distributor can be turned without force. With one hand holding the light on the timing indicator and the other available to rotate the distributor, find the proper timing position of the distributor. Disconnect and set the timing light safely aside, and tighten the distributor hold-down bolt so that the distributor is secure. If the idle speed of the engine changed due to the timing adjustment, use the screwdriver to adjust the curb-idle adjustment screw so the proper idle is attained. Reattach any hoses to the air filter assembly and reinstall.
