11 cab CMP Distributor question

[Lynn Eades]

I may have this wrong, but I think one set of points establishes the dwell and the other set triggers the spark. To check continuity through each set of points, you need to insulate/ isolate the other set of points by putting a piece of paper between the contacts. I hope that helps.
I have a timing jig, but could not figure out what I was doing. I had already ordered a Pertronix for it along with their coil. I installed them and the engine has never missed a beat.

[Brian Butt]

I'm the other half of the 15 cwt team at the Ontario Regiment Museum. We know the truck has a post war engine, but didn't know from what year, so '46 to '49 seems about right. Besides the engine, we know the transmission came out of a civilian truck, because the shifter is way too long, (Ape hanger comes to mind), I'll include some other pics, when I get a chance.
The other part of Mike's question was regarding continuity through the plug wires; We hooked up an Ohm meter, with one probe on the inside cap terminal for one of the cylinders, then the other probe to the clip that goes on the plug. No matter which wire we moved the probe to, it still indicated an open circuit. Shouldn't we be getting some sort of reading?
Now, if the plug wires are pooched, where could we get replacements?

[rob love]

The best wire to use is the steel core 7mm wire on these older systems. NAPA ha a semi tailored set, part number 700170 for around $63 ($45 if you are in the trade) that work fine, or you can order the wire in a spool and buy the ends in either bulk or individually. Personally, I buy it in bulk.

Napa also has the points set (CS47) but they aren't cheap at $65 ($40 trade).


You can likely get the stuff a bit cheaper thru specialty shops like Dennis Carpenter or Mac's.

[Brian Butt]

I'm the other half of the 15 cwt team at the Ontario Regiment Museum. We know the truck has a post war engine, but didn't know from what year, so '46 to '49 seems about right. Besides the engine, we know the transmission came out of a civilian truck, because the shifter is way too long, (Ape hanger comes to mind), I'll include some other pics, when I get a chance.
The other part of Mike's question was regarding continuity through the plug wires; We hooked up an Ohm meter, with one probe on the inside cap terminal for one of the cylinders, then the other probe to the clip that goes on the plug. No matter which wire we moved the probe to, it still indicated an open circuit. Shouldn't we be getting some sort of reading?
Now, if the plug wires are pooched, where could we get replacements?

[Brian Butt]

Thanks Rob, that will get us going in the right direction.

[Harry Moon]

Given the nature of the project, I would recommend if the budget permits, Petronix ignition and coil. Maintenance free after that. especially given how hard it is to get to the points.

[Lynn Eades]

But if you go the Pertronix way, there should be at least one resistor lead. Either the coil lead or the six plug leads, or preferably a full set. I bought a set from Magnacor.
It's not about radio suppression, but about cross fire (induction of a spark in the wrong lead (EMF?))

[MikeV]

So with the electronic system it makes sense to use it , since the vehicles sit for extended times with out running except for events at the museum.

But wouldn't we need to install crankshaft sensors and since we have a franken truck so to speak.

Wouldn't we need serial numbers off the engine to get the right parts?

[MikeV]

Here is another view with the distributor cap on the motor! before we removed the distributor

[Tony Smith]

Originally Posted by MikeV

So with the electronic system it makes sense to use it , since the vehicles sit for extended times with out running except for events at the museum.

But wouldn't we need to install crankshaft sensors and since we have a franken truck so to speak.

Wouldn't we need serial numbers off the engine to get the right parts?

I think you're approaching this with a "Modern Car" mindset. WW2-era vehicles remained unchanged for years at a time, and even then many parts were common to a lot of variations.

The "Rabbit Ears" distributor has exactly the same internal parts as the wartime "Crab Cap" distributor. In fact, as a museum piece you might light to consider changing the bails and cap to revert the distributor to a wartime appearance.

But for this discussion (for the '42 to '49 distributor), the only info you need to find the correct Pertronix ignition unit is the electrical set up of the truck; 6 or 12 Volt, positive or negative earth.

Some examples HERE

Perhaps one of the users on here of the Pertronix unit could provide a quick write-up or photos of the modification?