Setting the Timing
Now we will be setting our timing. That is the ignition timing not to be confused with valve timing that can only be adjusted on a few all out racing engines. What we are doing when we set the timing is determining when the spark ignites the fuel/air mixture in the cylinder. The ideal time is just before the piston reaches the top of the compression stroke. That way the gas has enough time to completely ignite and release it's power to drive the piston down as it moves past top dead center. If the timing is too soon the explosion will try to drive the piston back down as it is coming up. Not good. It can also cause a condition call spark knock, which simply is an uneven burning of the gases. (This can also be cause by low octane fuel) This explosion is not a steady push of power against the piston but more like hitting the walls of the combustion chamber with a hammer. Again not good. If the timing is too late the piston is actually running away from the explosion on its way back down and not fully benefiting from the expansion produced by the combustion. Both too early or too late can cause the engine to run hotter and make it work harder to do its job. The timing can be set while the engine is not running (static) with the exception to the distributor that has two vacuum advance lines that was on the early 70s motors. These are set with a strobe timing light at 5 degrees retarded or after top dead center while at idle. On most engines and most distributors a setting of 7-½ degrees advance or before top dead center seems to be ideal. The procedure goes like this. Bring the engine to top dead center on #1 cylinder.