Timing Lights

A timing light works by emitting a flash of light every time the #1 spark plug obtains voltage from the ignition distributor through the inductor signal clamp. When pointed at a harmonic balancer, the strobing effect the light gives off with a bright bulb lights up the top dead center groove on the balancer. This allows you to see exactly where and when the top dead center mark is in relation to the engine's timing pointer. Adjustments can then be made to timing by rotating the distributor to optimize the timing advance. The timing light is powered by either the vehicle battery or self-powered with small batteries installed within.

There are three connections when connecting a timing light, whether "old school" (simple), self powered timing light, or advance timing light. The positive and negative clamps as well as an "inductive" pickup / signal clamp. The positive and negative "alligator" clamps hook up to the vehicle's battery and the pickup / lead wire will clamp over / connect around the number one spark plug wire. Do not place any of the timing light wires in the way of moving parts (belts, fans, pulleys) or hot surfaces (exhaust parts). Next, start the engine and correct idle RPM to manufacturer specifications (typically 800-1000 RPM). To use the timing light, a trigger or button is pressed for it to begin flashing. When pointed at the harmonic balancer, you will see the cut groove appear as it is in the same spot as when the light flashes onto it. Then line up the groove with the timing pointer that is on the timing cover to set timing and correct degrees for your vehicle's engine (you need to research and confirm base / idle timing).

A digital timing light uses a positive and negative connection to the vehicle's battery for power. It also uses the inductive pickup clamp to connect to the #1 spark plug wire for an input signal. A trigger or button activates the timing light. In most cases, a digital version is a timing light with tachometer. The display provides a digital reading of the engine RPMs allowing you to see everything on one screen and monitor degrees of advance at any given rpm you choose. It also displays the timing advance in degrees digitally. Instead of a knob on the timing light there are "up" and "down" buttons that allows you to dial in to the exact degrees of timing that you want to achieve. Once you set the "target" timing degrees, you will then adjust the distributor until the timing groove on the balancer lines up with zero degrees on the engine timing pointer. You can also use this type of timing light to find out how many degrees the engine is currently set at. Simply press the "up" or "down" buttons on the timing light until the groove on the harmonic balancer lines up with zero degrees on the engine timing pointer. Then look at the timing light display and note what degrees are shown. This is what the timing is currently at on your engine. This function is designed to work for both base (idle) timing as well as total timing (base plus mechanical advance). This type of timing light helps provide precise and accurate timing with ease. However, this is the most expensive type of timing light.

A JEGS expert is ready to answer your questions and help you find the timing light for ignition systems that you require to tune and optimize your automotive street or race engine.