Many cars today use timing belts instead of timing chains that were used in the past. Most import automobiles use them and some new domestic autos are switching to them. There are advantages and disadvantages to using timing belts. Timing belts are more quiet than a timing chain. This is good for high performance applications that use knock sensors to detect detonation. The lesser noise minimizes the background noise caused by a timing chain. The downside is that the timing belt should be replaced every 60,000 miles. A timing chain will generally never need to be replaced. Many times people will wait past 120,000 miles and their belt will break. If the timing belt breaks the car will stop wherever it happens to be. Depending on what type of car you own the timing belt breaking can be very costly.
Small engine timing is completely mechanical. The coil is mounted closely to the flywheel. The flywheel is the large circle with cooling fins. The flywheel is on the opposite side of the engine from the output shaft. The flywheel has magnets mounted in it. As the flywheel magnets pass the coil they induce a current. The coil then discharges to the spark plug. The relationship of where the coil sits and where the flywheel magnets are, dictates the timing. The coil can be moved slightly to change the timing. Move the coil in the direction the flywheel moves and the timing will be retarded and opposite to advance timing. The only other factor that affects the timing is the flywheel. Occasionally the flywheel can shear it’s key on the crankshaft. The key locates the flywheel in the correct rotational spot to insure correct timing. If the key is sheared the timing can be anywhere, and the engine may spark but not run. The key is square and can be viewed from the end of the shaft. The key will have a cutout in the shaft and the flywheel. Offset keys purposely rotate the flywheel to advance timing.
Setting the timing on a vehicle is a simple task. First you must know what the manufacturer’s spec is for the stock timing. This information is usually under the vehicle’s hood. Many vehicles have their ignition timing set somewhere between 6 and 12 degrees advanced. Advanced ignition means that the spark that occurs in the cylinder happens earlier before the piston reaches top dead center. After you know what the timing spec needs to be you will need a timing light. Connect the timing light up to the battery or power source that it uses first. Next connect the clamp over the number one spark plug wire, which obviously runs to the #1 cylinder. This should also be marked on your distributor. If your distributor has a vacuum line running to it, remove the vacuum line and plug it so that it doesn’t suck in air. If this line is not plugged, the timing reading can be incorrect as the timing may be advanced slightly. The next thing you will need to do will be to locate the timing mark usually high-lighted yellow on the end of the engine or dampener.