I thought I would continue this thread since it has gone on for a while and it is lacking details.
I have a M51 5 Ton dump with the R6602 Gas engine. I converted the spark plug wires to civy wires ( covered in another thread ) and I have changed the points and condenser but the ignition
has been a downer for this truck. Even with new parts (likely Chinese junk) the points pit and become erratic after only a few hours of operation and that results in missing, fouled spark plugs, rough running and even more fuel consumption. Points suck.
So this is what I started with, the standard Delco Mil distributor with likely the original '62 coil.
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I left the distributor in the truck to do the conversion and that worked out fine. Remove all of the parts including the coil. Once the coil is unclamped, get under the truck with a stick and tap the coil out of the distributor. It slides out but it didn't want to come out after 50+ years..
View attachment 656145
So after all of the parts are removed I realized that the breaker plate is held in by two screws and is removable!
It has to be rotated counter clockwise just a little so that it can be removed without shearing off the incoming power wire.
I used a drill and removed the cam that is used to adjust the breaker points. Once that is out of the way, the plate that comes with the Pertronix kit slips over the brass points pivot pin.
There is a predrilled hole in the Pertronix plate and I lined up with center holes after the pertronix plate was slipped over the brass pin and drilled and tapped a 8-32 hole for a screw. There is an existing 8-32 screw hole in the original ste
View attachment 656146
So there is an issue with the original distributor housing. The replacement coil I wanted to use is slightly larger in diameter than the original Delco coil (which is obsolete).
This is how I dealt with the hole size issue. A 2 1/2" hole saw enlarged the shoulder in the casting. And a sanding drum opened up the hole for the coil body.
I used a battery powered 1/2" drill to do the enlarging. I get better control from the battery drills than a big honking 1/2" AC powered drill.
So here is the coil in place. I think the hole saw was 2 1/2" in diameter and the sanding drum was probably a 2" unit. I wore out one sleeve enlarging the hole. Not bad.
I did have to tap the coil into place with a piece of wood as it was a snug fit, but that is fine.
Here is the assembled unit.
This Pertronix unit is a standard 12 volt unit. I used a voltage converter externally to drop the voltage to the distributor.
This is mounted in the corner of the firewall next to the generator regulator box. I cut the 24 volt feed to the distributor and ran it to the red wire on the converter. The ground wires are tied under a screw next to the box - 8-32 worked fine again. The Yellow wire feeds the distributor power at 12 volts. Very simple.
This is the coil and the Pertronix kit I used. The Bosch Blue coil is known to be bullet proof and has 3.5 to 4 ohms of resistance. It is epoxy filled.
I would avoid the Pertronix coil. A company that sells kits for sailboat engines was selling the Pertronix coil and dropped it due to issues.
This is the power converter I used from Amazon. I tested the converter for several days with a 50 watt load - two 25 watt, 12 volt light bulbs... It runs very cool.
So after the conversion I thought I would start up the truck and hope that it ran so I could time the engine. There is a pointer at the front of the engine and there are two marks on the belt pulley. (Really, they are there but you will need to scrape to find them and then put chalk into the grooves so you can see them with a timing light) The first mark is the 5 degree before top dead center mark. That is the one you want to set the distributor to. What was incredible is that after the conversion, the timing was exactly correct !! Likely Pertronix designed their system this way but I was really not expecting that! Nice surprise. So I never had to adjust the timing. It just worked!
Results of this conversion so far look good. The coil was likely going bad (guess) and the truck was missing, the points were pitting in less than 10 hours. It was bad.
After the conversion the trucks runs amazingly well. I was able to idle the engine down to about 500 rpm which was not previously possible due to missing. It looks like a great conversion so far. I've installed another Pertronix on a gas sailboat engine and that was a huge improvement also.
So besides the parts described here you will need an 8-32 tap and drill and a couple 8-32 screws. Some misc wire.. I used 14 gauge THHN stranded wire. Some crimp butt connects and some ring terminals.
I understand that the 2 1/2 ton gas engines use an almost identical distributor so perhaps all of these parts will also work with those as well.
I am going to put another Pertronix kit into my spare parts along with another 24 to 12 volt converter. Getting stuck on the side of the road with a 5 ton sucks and spare parts are good to have on hand.
The Pertronix kit cost $85 off Amazon, the Bosch Blue 00012 coil was $45. The 24 to 12 volt, 10 amp converter was only $16. This is a very cheap conversion considering the cost of running these trucks.
