ignition timing and advance question, Pertronix, Ford 800

blue_tractor_man · Sep 13, 2009

I installed a Pertronix ignition in my Ford 851 (really a "64 4000 4 cylinder). I took the advance springs and weights out, cleaned and replaced them. I noticed that after putting in the Pertronix ignition that the timing no longer goes down to the 5 degrees advance that it did before. It starts at 15 degrees and goes on up to the factory spec 28 degrees. It seems that the original points had some effect on the original timing. The advance weight springs really do not begin to hold the weights back until the timing gets to 15 degrees. In other words, my tractor idles at 15 degrees and then goes on up to 28 degrees at full speed. It seems that the drag of the points on the cam had the effect of pulling the advance back to 5 degrees.

Does that seem plausible?

Also, why was the factory spec 5 degrees at idle? That seems like very little advance at idle. The tractor seems to idle just fine at 15 degrees.

Should I change anything or just run it like this?

John B. · Sep 13, 2009

15 degree may kick back when you try to start the engine but if it doesn't knock when idling it may be okay. I would check to see after running it with the new ignition and shutting if off to see if you can turn the rotor in the opposite direction of rotation to see if it moves back any. If you took the weights out you may have one that is stuck holding it at 15 degrees or if one of them has a flat spot on it holding it in the advanced position.

At idle an engine doesn't need to advance the timing much. The purpose of advancing the timing is that the fuel mixture only burns so fast no matter what speed the engine is running. The faster the engine speed the sooner the fuel needs to be ignited so the fuel is at it's maximum force when the piston is in the best position to take advantage of this force. This is the purpose of advancing ignition timing.

Blue-Tractor_Man · Sep 14, 2009

Yes you can turn the advance back when it is turned off. There is absolutely no resistance until the weighs hit the little leaf springs.

My theory is that the drag of the points on the lobe retarded the timing, but with the Pertronix ignition there is no drag.

Is it OK to leave the initial timing at 15 degrees? Seems like when i was hot rodding cars, the idling advance would be pretty high because of the vacuum advance. Never seemed to be a problem on my cars.

waltdavies · Sep 14, 2009

Did you put the springs back in the correct place it makes a big difference.
Walt

Blue-Tractor_Man · Sep 14, 2009

The springs are little leaf springs that are riveted onto the weights. they don't look like any other spring and weight system I've seen before. I looked in the parts manual and they appear to be stock. The little leaf springs do not look like they are meant to be tampered with.

ignition timing and advance question, Pertronix, Ford 800

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