The Ford 4.2-liter V8 engine is also known as the Ford 255 engine. The 1980 Ford Mustang featured the engine with an ignition timing of 6 degrees before top dead center. You should regularly adjust the ignition timing of older engines such as the Ford 4.2. It can be done with a some mechanical skills and a few automotive tools.
Make sure you have enough space to work on the engine before you begin adjusting the ignition timing of car. Place your key in the ignition and turn your engine on. Shut down any accessories and equipment in your vehicle.
Exit your vehicle and put wooden or metal wheel chocks on the front and back tires of the car. Reenter your vehicle and engage your car's emergency brake.
Put the transmission in neutral and gradually bring the engine to a warm idle speed of 550 rpm. Exit your car and open the hood to your 4.2 engine, allowing the rpm to go back to idle.
Locate the engine control module on the right side of the engine. It will look like a large computer chip. Turn the warm idle speed option on.
Attach the timing light to the car battery by putting the red clips on the positive terminal first and the black clips on the negative terminal second. Attach the timing light clamps the spark plug wire labeled "No. 1" and shine the timing light on the pulley connected to the main crankshaft.
See where the timing mark on the pulley is compared to the timing mark on the distributor housing. The distributor housing has a cap on it and is connected to the engines camshaft and oil pump. This will show you what the current ignition timing is; 6 degrees before top dead center (TDC) is the factory recommended ignition time for the 4.2 engine.
The distributor housing will have a lock-down bolt at its base. Use a wrench to loosen the lock-down bolt and disconnect the distributor vacuum hose.
Plug the distributor vacuum hose into the engine control module. The engine control module should have multiple ports for you to use, but you may have to pull back the plastic protection on the ports. Disconnect the 3-pin switch assembly on the engine control module.
Ground the carburetor switch with jumper cables by placing the red clamps on the switch and the black clamps on the ground.
Rotate the distributor with your hand until the timing mark on the distributor lines up with the timing mark on the pulley. 6 degrees before top dead center is the factory recommendation for the 1980 Ford Mustang equipped with the 4.2 engine, but the timing may be slightly different for you vehicle.
Remove the jumper cables from the carburetor switch. Unplug the distributor vacuum hose from the engine control module and reconnect it into the distributor housing before tightening the lock-down bolt with a wrench.
Remove the timing light clamps from the spark plug wire and take the clips off the car battery. Turn off the warm idle speed option off and close the hood.
Enter the car and put the transmission in park. Exit the car and remove the wheel chocks from your tires.
