MV ignition distributor with Civilian Wires - Steel Soldiers::Military Vehicles Supersite

Dave911 · 08-10-2009, 21:50

I think I have read all of the threads on the forum regarding Military ignitions on the gas truck engines. I've struggled with my Continental R6602 gas engine in my 5 ton for some time. Plug fouling, back fire problems, etc. I replaced the cap and rotor, points a couple of time. Plugs 3 times etc. Nothing got a lot better. Things seem to have gotten worse over the last couple of years so I thought perhaps the plug wires? I called Memphis Equipment about a new set of plug wires - over $250 for new ones. So I decided I could screw up a couple of times trying to get standard wires to work on the military distributor. After some serious head banging I think I found a good solution and I wanted to share it so you can avoid the head banging yourself.

I took three of the old plug wires and used a cable cutter to cut off the ends and about 1" of the tube and braided portion back from the nut flange and pulled out the old wire. So I was left with some of the woven brass braid on the outside, a thin brass tube on the inside and the fitting that is soldered to the tube. (Both ends of the wires are identical) After using a tapered punch to make the brass tube and braid round again after they were sheared off via the cable cutters I found that a 7mm spark plug wire would fit down the tube perfectly. But how to secure the wire into the assembly so it doesn't fall out?

I decided to use some rubber electrical splicing tape. I stripped the ignition wire back at the end about 1/4" to expose the solid conductor (I used solid wire ignition wires) and splayed the strands in all directions, pushed on the mil ignition wire end salvaged as described. I then wrapped the rubber splicing tape around the wire about 7/8" of an inch from the end of the wire and continued to do so until the diameter of the tape wrap was just a little smaller than the hole in the top of the distributor. I then slide the wire with the tape wrapping into the distributor cap and pushed the nut down onto the rubber and threaded the assembly into the cap. The cap squeezes the rubber tape into the hole compressing it onto the wire and at the same time drives the wire against the metal contact in the cap. I snugged the nut down with a wrench and checked the wire for continuity to the arc contact inside the cap. If everything is right you should see about 5K ohms of resistance. Apparently these caps have built in resistors. Do this 6 times and you have a retrofit mil to civilian wire cap assembly.

The rubber splicing tape is unique in that it bonds to itself as you stretch it. I was concerned about the plug wire coming loose inside the cap and breaking the electrical connection, so after I did a test. I took apart the first one I put together. I backed off the nut and pulled back the mil end off the distributor and the tape had formed a solid slug of rubber in the hole. I pulled on the wire and it took a good 30+ lbs to get it our of the rubber plug that was created by the tape. So with the nut on, those plug wires are certainly not going to fall out anytime soon.

The improvement is remarkable! The truck starts and idles like never before. No sign of plug fouling yet at all. I used some Autolite resistor plugs - similar to AC Delco R46's. The plug wires I used are stranded wire set (non resistor) that I have used for farm tractors before. Belden makes them and Napa sells them. Very high quality silicone 7 mm - about $20 for a 6 cylinder set.

I should have done this years ago.

Time to haul some gravel!

Dave911 · 08-11-2009, 07:55

FWIW, the spark plug wires I used were Napa # 700173. This is a 6 cyl generic set of wires - solid wire - non resistor

I have found that NAPA is one of the few auto parts suppliers who still stocks real wire spark plug wire sets. I asked Advanced Auto about them and all I got was a blank stare.

Barrman · 08-11-2009, 10:44

Looks good. Just for fun, go north of town to the airport and visit with the mechanic. He might have some aircraft plug wires sitting around. Depending on the models, some of them might fit the military cap and plugs.

The A&P in Kendallville used to be named Williams. If he is still there, he would probably love to help you adapt aviation wires to the truck. Seems like you got it running good now though.

Dave911 · 08-11-2009, 11:37

Aircraft plug wires are compatible with Military vehicles? Geez, I didn't know that!

That sort of makes sense. I might have gone that route had I known that. There are a number of small airports around me (I'm northeast for Fort Wayne) that have service shops attached.

If this doesn't work out long term, I'll be stopping by some airports. But my fix looks like a good solution so far.

It is hard to beat $2.00 spark plugs available everywhere!

I've got these same plug wires on two tractors that spend most of their time outside and one set of wires is over 10 years old and still going strong.

For my next change I'm considering installing an MSD coil driver box - they supply multiple sparks at low speeds. If I can get another fraction of a MPG out of this thing gas consuming - OPEC loving engine, that would make the effort worthwhile. I've already got one handy, but it is down my list of things to do quite a ways at the moment. I think I need to spray some paint first, recover the drivers seat, replace a cracked windshield pane etc etc....

If I have to get my todo list done before I die I will live forever!

Barrman · 08-11-2009, 11:51

I was thinking of Smith field when I wrote the above. It has been a few years since I was there, but either Angola or Goshen has a pretty big maintenance shop that probably has some spares sitting around for you to play with.

If you can get better mpg out of a Gasser, please pass along what you did. I get 4.95-5.05 on my M35 Gasser emtpy or loaded, fast or slow. I don't want to do the civi distributor however since the truck is pretty much authentic 1952. Electronic ignition inside the distirbutor is something I have been considering.

Dave911 · 08-11-2009, 12:27

Yep, Smith field and Auburn airport are about the same distance from me. For a while they were talking about closing Smith field - the big Baer field airport guys were trying to shut down Smith field. Fortunately common sense prevailed and they kept Smith open. There are a lot of small airfields in Indiana.

5.05 tops - I thought they would get 6-7 or so? My M51 gets 4-5. I think the best chance for increase MPG would be radial tires, front locking hubs and possibly electronic ignition like the Pertronix or even better an MSD unit. The MSD units can gain efficiency with the higher plug voltage, wider plug gaps, and multiple sparks. I had an old van with a 350 chevy gas engine that I was having problems with - stalling, rough idle etc - probably in part due to some older gas - a tank full of it, and it was equipped with an HEI ignition. I wired in a 6 series MSD unit that I had temporarily since I thought the HEI was having a problem firing the old gas - what a difference. Starting was no longer an issue and stalling problems disappeared as well. The MSD units simply work.

I can understand not wanting to mess with an original setup though. Although I'd consider painting a MSD unit camo

My M51 gets used and driveability and MPG is more important to me that originality.

Stretch44875 · 08-11-2009, 13:06

I cut the civi wires off with some wire sticking out, then used a piece of 3/8 fuel line around the wire to fit it in the hole on the distribuator. Had to put a little grease on everything, then it slid nice and snug in the hole. Seems to be waterproof too.

Dennis

JasonS · 08-11-2009, 13:20

The best thing I ever did for my deuce was convert to a civilian distributor and a Pertronix electronic ignition.

We converted my brother's 602 military distributor to electronic ignition and it made a nice improvement.

m139h2otruck · 08-11-2009, 13:53

We had M-Series Rebuild, LLC in NC install an electronic module (Pertronix) in a spare distributor from the parts truck. Told us it was the first one that they had done in a 5 ton. It was a little pricey, but fired off with the first turn of the starter. Not really much difference in running, but should never have to worry about point burn or breakdown.

Not sure you can install an MSD, as they are normally only available in 12 volt.

Your existing spark plug wires must have been very worn or leaking to have the problems you had. Ever check them at night with the engine running? Ours are original as best I can determine, and they have had no problems to date. Plugs are the same as we installed in 2006, when we got the truck. Did use a much hotter set than what was in the engine.

These engines, like a lot of six cylinders, have problems with vacuum leaks at the manifold to head location. Need to check with WD-40 or unlite propane torch.

Dave911 · 08-11-2009, 18:37

MSD - on 24 volts.....

Yep, I'm sure the wires were shot. 20-20 hindsight

>> running it at night

I don't think that would help much since if the wires were arcing to ground, they would be doing that between the inner core and the brass tubing shell - so you would never see the arcing anyway.

24 to 12 volt switching power converters are getting pretty cheap now. I think I have seen something in the 10 amp range for about $50-$75. The MSD 6 series I believe draw about 5 amps max.

I looked at using some fuel hose to fit inside the distributor hole but the stuff I had did not fit well enough IMO. That's the nice thing about the rubber tape, you can wrap it until it fits perfectly and then once compressed it glues itself together into one chunk of rubber. Neat stuff. After the nuts are tightened there is no way water is going to get inside that rubber seal. So although I didn't really think of it I guess the distributor is still water tight even though the spark plug to spark plug wire connection is not.

>>Need to check with WD-40 or unlite propane torch. Good point - I'd do that if I had any misses but the motor is rock steady now. No more missing.

Dave