its kinda a bad question, but what do you use a timing light for and how do you use it?
pete

 

OK. Here goes
A timing light is nothing more than a strobe light. Most timing lights today are powered from the battery of the vehicle and have a inductive pickup that is in the form of a clamp that is clamped to the number one spark plug wire. Some of the early timing lights
were a neon bulb that was connected in line with the number one plug wire and the neon was lit by the energy going to the plug. If you look at a electric fan and blink your eyes fast enough the blades will seem to stop. This is what a timing light does. There is a mark on the rotating crankshaft vibration damper, in the form of a scribed line, and a scale of 0 to 15 usually by 2's bolted or cast in to some stationary part of the engine near the vibration damper, on the 4.9l six it is a metal tab bolted to the left lower timing cover bolts. this tab is level with the outer diameter of the crank damper and if the engine was not running you could line up the scribed mark on the damper ( by turning the engine by hand ) with a number on the timing tab. The numbers indicate the number of degrees before top dead center ( advance ) of number one piston. If you want to know where the number one spark plug is firing and thus set the amount of initial advance ( 4.9l = 10 Before top dead center) or even retard ( the number of degrees after top dead center ) You can either BLINK YOUR EYES real fast ( Ha )or use a timing light when the eye blinking routine doesn't work. The timing light being connected to the number one plug wire will light , flash, when the distributor sparks number one plug. This very bright light , being pointed at the scale and the rotating damper,will make the rotating scribe mark on the damper visable and seem to stand still as it only flashes when number one plug fires. This fools your brain as all you see is the lit up mark and not the rest of the unlit damper so it stands still.Now you can rotate the distributor , clockwise or counter clockwise, and change when the plug fires ,either advance or retard . Rotating the distributor will change the time the plug fires and also because it is connected to the no.1 plug ,the time the light flashes. This timing is all related to where the No.1 piston is on the firing stroke either before the piston hits the top ( advance )or after the
the piston goes past the top of the stroke ( retarded). By changing when the timing light flashes , by moving the distributor. The mark on the damper will seem to move and line up with a different number. So by using the timing light to illuminate the mark on the damper and by rotating the distributor slightly you and set at how many degrees advance or retard the plug will fire. This is based on number one cyl and no others.

Bob / stractor