Timing retarding 2* after installing crank trigger

[Ron Finney]

Originally Posted by pmrphil

Try checking your timing and then rotate the distributor a bit (either direction) and you will see that timing doesn't change (if you're using a crank trigger) the only thing that changes is the position of the rotor in relation to the plug wire tower in the cap. It has no effect on timing events until you turn the dist so far that the spark is transferred to an adjacent tower. The spark is signalled by the trigger, not the dist.

Your observations are correct, but your conclusions are incorrect. The spark (ie. coil) is being signaled by the crank trigger but the spark generated by the coil is being delivered by the distributor, and the timing light is being triggered by the spark in the wire, not the crank trigger. While the change is small, there is a change. The reason you don't see change with the light is that the spark is jumping the gap to the terminal and with the speed of electricity, and the width of the tab on the rotor you are not going to detect that with the flash of the timing light. But, since the spark is being delivered to the terminal in the cap via the tab on the rotor...if it gets there sooner or later...the timing IS changing.....what you are doing is moving it from the center of terminal slightly, yes it is still firing the light the same, because the spark is still jumping the gap. If you were to move the rotor phasing to the edge of the conductive plane, then try moving the distributor you would find that you start killing the cylinder....the spark would now be getting there to late and the gap is too large for it to jump. Granted, this is extreme, but it will show you that moving the distributor will affect timing. If you were to use a scope rather than a timing light to look at the signals in real time, you would see the timing change as well.