Ignition Timing Adjustment

Ignition Timing Adjustment

Maximizing your vehicle's power and mileage

Regardless of make or model, basic automotive engine maintenance is generally divided into four categories: lubrication, fuel, intake/exhaust, and ignition. Most do-it-yourself enthusiasts have no trouble with routine oil changes or air filter replacements, but giving your ignition system a tune up is a little more technical and is often met with some apprehension. It is true that some specialized electronic gadgetry is required, but the equipment usually costs less than a single trip to the local mechanic and will become a welcome addition to your automotive tool arsenal. You'll need a timing light (available at nearly any auto parts store), a tachometer (if your vehicle's instrument panel doesn't already have one), and a small selection of basic hand tools.


To prepare for the adjustment, ensure that all other systems on your vehicle (airflow, fuel pressure, idle rpm, etc.) are operating properly. Though not necessary to set ignition timing, this would be an ideal point to replace your spark plug wires, distributor cap, rotor and spark plugs. Connect the timing light (and tachometer, if used) to your vehicle's battery and No. 1 spark plug wire per the manufacturer's instructions. Check the vehicle specifications to determine the proper timing advance (often noted on a sticker on the underside of the hood), read in "degrees before top dead center" at a particular rpm. In this case the recommended advance is five degrees at a 750-rpm idle. Being very careful to avoid entanglement with moving belts and pulleys, start the engine and bring to normal operating temperature and specified rpm. Direct the timing light to the main crank pulley, and observe where the timing mark on the pulley falls compared to the degree tab on the front of the engine. If the marks line up properly, the ignition timing is correct and no adjustment is necessary. If not, your engine's power and mileage have likely suffered and adjustment is required.


Looking near the base of the distributor housing, find the distributor lockdown bolt. Loosen the bolt just enough so that the distributor can be slowly rotated by hand. You may want to scribe match-marks on the housing and head (or intake depending on engine type), so that you can return to the original setting if desired. Again using the timing light and observing the mark on the main pulley (with the engine running as before), gently rotate the distributor housing until the timing mark drifts into the proper position relative to the degree tab. Tighten the lockdown bolt on the distributor, and give the timing mark one last look to ensure the distributor didn't accidentally move out of position. Your ignition is now calibrated per the manufacturer's specifications, optimizing your vehicle's power and mileage and minimizing exhaust emissions.

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