Distributor Tech Tips


What Do I Have vs. What Should I Have

When performing maintenance, it is critical that you know and understand what part you are working with. The distributor on your F-134 is no different. Whether you are buying parts for a tune up, an electronic ignition upgrade or perhaps a whole new distributor, it is critical that you buy the correct parts. Luckily, most distributors have a metal tag riveted or screwed to the casing that tells you what type it is. However, sometimes that metal tag is gone after fifty plus years of faithful service. If this is the case, fear not, there are other ways of identifying your distributor model.

Eddie was looking for a way to tell what type of distributor he had. "How do you tell if you have an IAY or an IAD distributor? What would most likely be in a '62 3B?"

Nick responded: "Both types of distributors will fit the same engine. I've already had to change mine from an IAD to an IAY. From what I've learned over the past couple of days, some of the more obvious differences are as follows:

Oldtime provided some good information: "As you know there are several distributors that can be interchanged; IAD, IAY and IAT. The IAD models were used for all CJ-3As and also early CJ-3Bs. All IAD models were originally 6 volt systems yet these can be used as 12 volt systems by using a proper condenser. For quick Identification; the IAD models have a dust shield below the cap. The cap spring clamps and the oval shaped aluminum identification tag are both riveted to the housing.

"The IAY models were initially 6 volt, but most were 12 volt systems. These were used on CJ-3B, CJ-5 and CJ-6. The 12 volt systems became abundant in 1958. Most but not all post 1958 systems will be 12 volt. 1958 itself was a year with both systems and a 6 volt option was available for several years thereafter. The aluminum IAY identification tag is the shape of a house and it is screwed on under one of the cap spring clamps. The IAT models are generally vacuum advance distributors that are used with wagons or pickups.

"All of these different distributor models were used for industrial Jeep engine applications. The CJ-3B should have the IAD (early) or the IAY (later). The IAD and IAY models use totally different engine block advance arms (mounting plates)."

Bruce Teterin found distributor numbers in the Jeep Universal series service manual SM-1046 and the Service Manual for Jeep utility vehicles. "Could somebody please tell me the differences between these Prestolite and Autolite distributors for the F4-134 motor?

Wes K answered:

"Models that I have listed as 'same as above' have minor variations in their advance curves."

Tom Callahan inquired about some additional models: "Where I can find information on other distributors that apparently were used by Willys? My '53 3B has an IAD-4008, which appears to be stock, and I also have an IAD-4041."

Wes K responded: "The IAD series were dustproof. They had an extra cover that went over the points, but under the cap. The correct for your 3B is an IAD-4008A. The IAD-4008 was an L-134 distributor. The IAD-4041 is for an early '54 and later CJ5. There are over 100 flavors of IAD series distributors."

Note: see also Delco-Remy Electrical Parts: Service Manual correction for 1959-60 Jeeps.

Distributor Manuals

Chuck brought up the point that: "I have seen various distributors listed in Chilton's and the other manuals, but do they have individual manuals that pertain specifically to singular models?"

Wes K listed a few manuals that he had come across:

"When Prestolite acquired Autolite's generator, starters and distributors in the 60's, I've only been able to find the large Prestolite service manual which is merely a collection of service letters but very useful. If you wanted at least one nice bench top service guide, I'd opt for the military manual."

Note: see also Distributor Installation: Service Manual addendum for post-1954 Jeeps.

L-head and F-head Distributor Swap

Ron inquired: "Can I transplant an IAD 4008 distributor from a 6-volt L-head to a converted 12-volt F-head motor? The early L-head was chain driven while the F-head is gear driven and they have different rotations."

Uday Bhan Singh answered: "The rotation is not the problem. One can easily use the distributor from the Go Devil in a four cylinder Hurricane. The ignition coil is only to be changed for voltage. One point to highlight is that some distributors have a vacuum governor, and they should have a matching pipe line with the carburetor to advance the firing."

Rossco said: "Just because the cam rotates the other way doesn't mean the distributor has to, but if it does turn clockwise then you can't use it. The mechanical advance wouldn't work for a start."

Oldtime replied: "It is my opinion that the Autolite IAD 4008 distributor is an excellent quality ignition component. It will easily interchange with the original distributor for your F-134 application. The main differences would be that the IAD 4008 has a dust seal, different cap and different rotor as compared to the IAY distributors. Perhaps the main concern would be the condition of the distributor shaft bushings. If the shaft is tight (side play), you're alright. Make sure that you read the manual to install it correctly. Basically, the rotor will be in the 5 o'clock position with the #1 cylinder TDC. The shaft is slotted off center, but the 5 o'clock position will possibly help ease with realignment. Remember that the shaft will have to rotate into its final position because of the gear engagement.

Ron provided an update: "I removed the 4008 model out of the old engine. It was seized to the oil pump due to rust. There is much slop in the side play of the shaft. I'm going to keep the old one in until I can get a newer one."

Anon suggested: "Why not just put new bushings in? I've made all kinds of bushings for repair. I think places like Walck's might do it for you."

Oldtime added: "If memory serves me correctly, the IAD 4008 distributor shaft is interchangeable with the IAY shafts. It's a good idea to thoroughly dismantle them if you are a conscientious rebuilder."

Distributor Bushings and Oiling

Pete posted the problems that he had with his distributor and the steps that he took to correct them. "My engine was stumbling (un-drivable) above idle, slight miss at idle. It worsened until idle no good either. I added an inline fuel filter, blew out the fuel lines, rebuilt the carburetor, checked the compression and valve lash on new engine, checked the spark plugs and wires and replaced the coil.

"The final cause was that there was too much play in distributor shaft. Moving the top of the shaft would affect points gap by maybe .030. So, changing point gap, loss of point gap and rotor striking cap towers, which might have been a bad rotor, equals no spark to the spark plugs.

"My local machine shop fixed my distributor. My new/ rebuilt distributor housing was re-bushed. There was no evidence of how the oiler could get oil to the shaft, so the machinist drilled a hole in the bushing where the oiler tube mounts. I put it all together and the engine ran nice and smooth.

"After the engine ran about five minutes, a squeal started and it ended up being the new bushing burning up; the shaft was frozen in place. Determined that the new bushings were not being lubricated properly and/or wrong bushing material was used. Using best of all parts, I assembled my old distributor to obtain another good setup. This time, I made certain that all parts started off good and lubed and verified oil could get through bushing to shaft. It now runs fine.

"Here are some lessons learned:

  1. Granville King (The Jeep Bible) said 85% of the time it's ignition over fuel. I now have that lesson burned into my brain and I will do troubleshooting in the future, not trouble assuming.
  2. Distributor bushing material must be porous. As I cleaned my distributor housing and blew air through the oil hole, I could see bubbles blowing through the bushing; there was no drilled hole. (The bubbles were from brake cleaner I was using to clean it).
  3. There is an oiler wick in the top of the distributor under the rotor and another in the housing/shaft oiler hole. Use them.
  4. Make sure and lube parts well while assembling. I used Lubriplate.
  5. The new distributor from Krage did not use bearing material with vertical grooves on the outside bearing surface. The distributor I'm putting in next does have these grooves. The grooves may aid in oil distribution up and down the outside of the bushing to the gap between the upper and lower bushings, allowing better lubrication. Perhaps the engineered lubrication comes from both methods, the grooves, and the porousness of the material.
  6. Buy a matched cap and rotor set locally. Get your points and condenser at the same time. I bought a cap that is so sloppy that it doesn't fit the distributor tightly and the clips won't hold it on. I also bought an extra rotor and the tip is too long; it strikes the cap towers! Even with the bushings replaced, I could hear and feel it hitting, even before I installed the points plate."

Bruce W added: "I recall when I was knee-high, whenever my Dad checked the oil in the car or pickup, he would pull the dipstick, look at it, then open one of the oilers, on the generator or distributor, and drop in the drop of oil that was ready to come off the end of the dipstick; every time. Not clean, new oil, but oil nonetheless; and often."

Thanks to Tech Editor Doug Hoffman, and all the contributors. -- Derek Redmond

Return to CJ-3B Specs and Tech Tips.

FacebookVisit CJ3B.info on Facebook.

CJ3B Home | Contents | Search | Links | 3A and 3B Community

Last updated 6 January 2009 by Derek Redmond redmond@cj3b.info
All content not credited and previously copyright, is copyright Derek Redmond