Most any hobbyist familiar with engine tuning can relate to the usefulness of an inductive timing light. It consists of a strobe that's triggered by the electrical impulses passing through a spark-plug wire. As the strobe illuminates upon cylinder firing, it makes an otherwise variable Top Dead Center (TDC) mark on the harmonic balancer appear fixed, allowing the operator to compare it to a series of graduated stationary marks on the front cover, to measure spark timing.
As engine speed increases and the distributor advances, the balancer's variable mark follows and at some point can't be referenced to the stationary marks. In order to measure spark lead at all times, some hobbyists have modified their Pontiac's original harmonic balancer, adding one or several degree marks to it, while others simply purchase an aftermarket balancer that's completely indexed. Spark lead can then be determined when the appropriate variable degree mark reaches the stationary marks of the front cover.
Though these methods work well, it may not be convenient for some hobbyists to remove and modify their Pontiac's original harmonic balancer or lay out cash for a fully indexed aftermarket unit. Others may want to simply verify the accuracy of their modified original or check a new balancer's correctness. In these instances and many more, an adjustable timing light can prove an invaluable resource for any tuner. It uses an internal microprocessor to delay the strobe a selected degree, realigning the variable TDC mark on the balancer with the front cover's stationary marks.
The accuracy of the various adjustable timing lights presently on the market can range from poor to superb, and retail price isn't necessarily a separating factor. Since such a light might be used to tune a high-dollar engine, precise accuracy is required--even the slightest variance could lead to engine failure from full-throttle detonation. We routinely verify the accuracy of our adjustable timing lights using an engine with a fully indexed harmonic balancer and suggest the same to our readers.
Follow along as we provide six common uses for an adjustable timing light using Actron's No. CP7529 Digital unit. After connecting the clips of its power cables to the corresponding terminals of a 12-volt battery and clamping the inductive pickup to the No. 1 plug wire, taking all appropriate safety precautions, we started our Pontiac and let it warm to normal operating temperature. We then disconnected the vacuum advance canister, plugged its source, and got to work.