Wiring changes for new distributor & coil

I'm in the last stretch of getting these engines together. I'm trying to figure out the wiring harness for the new ignition. The new engines have Mallory YLM624AV Breaker-less Distributors, Mallory Pro Master 9-29723 internally resisted coils and Edelbrock 1409 carbs with electric choke.

Questions:

1) Is the orange accessory wire ignition switched? I need an ignition switched 12 volt source for the electric choke.

2) The gray electronic tachometer lead (Pin 2) is connected to the coil "-" terminal as stated in the service manual. The Mallory diagrams clearly call out connecting all wires originally connected to the coil "+" terminal but say nothing about the coil "-" terminal. I'm guessing this is the only place this could connect. Is that it is correct?

3) With the internally resisted coil, I now have the Yellow & Purple harness lead connected to the starter "R" terminal an the purple wire from the starter "R" terminal to the coil "+" terminal. The Yellow & Purple originally went to one side of the ballast resistor with the purple wire from the coil going to the other side of the resistor and the "R" terminal on the starter. I'm just closing/cutting off the unused pigtail.


Anyone familiar with this set up? I'm also curious about how the electronic tach works and what the yellow wire on the purple & yellow connector does. Is the yellow the exciter on the alternator?

Best thing to do is test the orange wire to see if it is switched. My experience indicates most are NOT tied to the ignition switch. You usually have to use the purple lead from the key.

The grey tach lead goes to the coil's - terminal.

You should tape the lead from the R terminal of the solenoid. The internal resistor coil has no means to use it.

The lead from the R terminal provided battery voltage to the coil during cranking. It bypasses the ballast resistor as well as any voltage drop from the key switch.

Most all tachs are 'electronic' in nature. They measure the frequency of the pulses from the coil's - terminal and convert it to a calibrated voltage (or current) source to drive the meter (display). The all digital ones are simple frequency counters with the appropriate scale factor for the number of cylinders used. You can build a functional one pretty cheaply using a "frequency to voltage converter" chip and a few other components.

Thank you yet again makomark!

The purple wire from the "R" terminal to the coil "+" is separate from the harness. I'll just remove it altogether.

Great info on the Tach. I never put much thought into it and assumed it was resistance based similar to the temp gauges. I picked up a Tach/Dwell meter from Harbor Freight when I bought the boat. It was about 20 bucks.



My dad was a mechanic with Cadillac, his Snap-On Tach/Dwell meter was the size of a lunchbox with the galvanometer. From the 60's or early 70's. Pre AD converter. I was too young to pick up, let alone retain, much of his knowledge when he passed. About all I remember is that he had every tool imaginable and they were much nicer than what I have today.

good to remove it since it is not integrated into the harness.

Sad about your Dad, especially his tools. I have several "quality" snap-on items that are ancient. Many of their newer items are overpriced, imported pieces of metal. What used to be a guaranteed, long lasting investment has become a coin flip for many items.