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Slight Differences in Distributors |
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jgodfrey 
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Joined: 07 Oct. 2020 Location: Shakopee MN Status: Offline Points: 663 |
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 Topic: Slight Differences in DistributorsPosted: 27 June 2022 at 10:11pm |
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I have been chasing so many things lately I've lost track. But I feel like I'm right there at the end. Then this happens.
I have been trying to get my timing set with the help of Scoutpilot. Rick and I spent some time on the phone going through some checks on the points, etc. I was still having an arching issue on the distributor which was causing intermittent misfires at idle. So, tuning it with that issue going on is impossible. I decided that since I had replaced everything from the coil, to the wires, to the cap and rotor, that the last piece would be a new distributor. I was going to have mine rebuilt until I saw the following chunk missing from mine.  My thought was that it could be the source of the arching, but it could also be the top post insulator failing. Either way I started looking. Pete Debella and Army Jeep Parts have an Auotlite "replacemet" or a cheaper non-descript version for half the price. I called Midwest Military and he happened to have a NoS Prestolite IAD-4008A in stock.. I bought it and tried to install it. But it bottoms out in the block before the shaft reaches the oil pump. I was careful not to turn over the engine with the distributor out because of the clocking of the oil pump. Bit since the shaft fell short of the notch it cranked without spinning the rotor. It felt like it dropped right in, so I didn't try to turn the rotor before tightening it down. Plus, the cap was already on. Either way, it did not get to the notch. The overall length of the shaft is the same, so are the other important dimensions - except 1. In the picture below you'll notice there is an O-ring on the new one that mine didn't have. This extents that part by about 3/16 of an inch. This is my old one.  This is the new one.  I would really love to keep this distributor. I looked at the diagrams but can't determine if I can swap these pieces between them. The bottom bushing on mine looks like it has solder or some other material where the set screw. The new one has a set screw. I'm assuming the top bushing would be the same. Here is where it bottoms out in the block. I was not aware there was a difference in the depth of this hole in the block.  Any thoughts on this situation would be helpful. Thanks Edited by jgodfrey - 27 June 2022 at 10:25pm |
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Joe DeYoung
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Posted: 28 June 2022 at 10:01am |
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Post deleted due to incorrect info.
Edited by Joe DeYoung - 28 June 2022 at 11:10am |
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Joe DeYoung
to many jeeps, parts, and accessories to list here, but apparently enough to keep me in trouble with my wife. |
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Joe DeYoung
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Posted: 28 June 2022 at 10:03am |
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Also, maybe it's an optical illusion, but it kind of looks like there may be something in the slot of the oil pump shaft preventing the tang of the distributor from engaging it.
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Joe DeYoung
to many jeeps, parts, and accessories to list here, but apparently enough to keep me in trouble with my wife. |
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jgodfrey
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Joined: 07 Oct. 2020 Location: Shakopee MN Status: Offline Points: 663 |
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Posted: 28 June 2022 at 10:45am |
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I can't explain it, but that bore changes diameter just short of 2" in. It narrows by half. John at Midwest Military had never heard of that either, but it hits solid in there almost a half inch short of where it needs to be.
Maybe this picture will help. The red is the outside diameter of the hole. The green is a tapered bore that leads to the yellow, the inside diameter of the shaft leading to the oil pump. The end of the distributor housing that guides the shaft is too long and too wide for the final ID of the hole.  If the bore was the same diameter all the way through - that would be awesome. I could have put that thing right in. But in this case it bottoms out hard, metal to metal. Do I have some kind of a unique (cursed) block? Here is a slightly different angle. I don't know what that dark spot is in the bottom, but it might be assembly lube I put on the o-ring trying to get it to slide in.  Thanks
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Joe DeYoung
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Posted: 28 June 2022 at 11:09am |
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I checked a bare block on the floor and sure enough the bore is not the same all the way through... So I my memory sucks and am wrong about the the bore. I've amended my earlier post. The 641087 block I am referencing is finished bored about 1.75" deep to match the distributor, then ruff drilled another .50" inch to a depth of 2.25", then is about a 3/4 diameter (eyeballed) through. Looking at your tape measurements, it should still work in the block that I have.
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Joe DeYoung
to many jeeps, parts, and accessories to list here, but apparently enough to keep me in trouble with my wife. |
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jgodfrey
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Posted: 28 June 2022 at 12:00pm |
I tried hard to get it to go but it is a metal-on-metal fit inside the bore. When you look at the picture it is closer to 1 13/16" when you reach the shaft bushing. It is tapered, so it gives the illusion that it will go right in, but I worked at it for over 30 minutes. I was going back and forth from mine to the old one trying to see if I missed anything in how I was inserting it, but my old one went right in every time. |
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Oldpappy
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Posted: 28 June 2022 at 11:19pm |
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I have swapped Autolite and Prestolite distributors without any problem.
What you have going on is a mystery to me. The slot in the oil pump is offset, so the tab on the distributor shaft has to be in alignment with that. Are you sure you have that right? Looking again at the picture it looks like there is a chunk of the old distributor shaft tab in the oil pump slot?
Edited by Oldpappy - 28 June 2022 at 11:26pm |
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If you can't get there in a Jeep you don't need to be there!
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jgodfrey
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Posted: 29 June 2022 at 12:22am |
It seems to be a mystery to most. That is a shadow on the slot. It's not obstructed. This model of Prestolite has a longer casting around the upper shaft. Both are identical overall lengths with offset tabs. Everyone I ask says they've never seen that. What that means about my block, I have no idea. My SN is relatively low (46877) but the deck has been planed twice in the 46 years we've owned it, so I have no idea what the date or origin of the engine is. It appears to have never been black.  When I was doing my teardown I discovered that the timing cover and driver's motor mount were from a 3A. It was reversed. I corrected this but combined with the greenish color, which appears to be the only layer of paint that can be found in every nook and cranny, points to this not being the original engine. So, did they change something in that bore whenever this was made? Is this an earlier or later engine than what aligns to my build date? Is it an early block that had 3A parts added? Or a factory block that was built up and painted green by someone? All I know is that it's been this way since we've had it, and the 1-off scenarios keep causing me heartburn. I'm hoping John at Midwest has the rebuilt distributor soon. I went over the steps to tune it today with Rick, so I'll know soon if that's the source of some heat. If I end up swapping the distributor I'll tune it again to get the process embedded in my head.
Edited by jgodfrey - 29 June 2022 at 12:27am |
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Mark W.
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Posted: 29 June 2022 at 8:52am |
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if the block was decked it was most likely also hot tanked which would have chemically removed any and all paint. So it could have very well been originally Black or any other color 134Ls came in.
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Chug A Lug
1948 2A Body Customized 1949 3A W/S 1957 CJ5 Frame Modified Late 50's 134L 9.25"clutch T90A D18 (1.25") D44/30 flanged E-Locker D25 5.38 Since 1962 |
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Oldpappy
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Posted: 29 June 2022 at 9:23am |
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I have an early 2A block and a 3A block down in the barn. I don't expect to find differences in the distributor bore but this conversation prompts me to look at them.
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If you can't get there in a Jeep you don't need to be there!
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jgodfrey
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Posted: 29 June 2022 at 9:47am |
I'll be swapping it out with a rebuilt IAD-4008 today, so I will try to take some better measurements and pictures. It sounds like what Joe DeYoung measured was about the same as what I have.
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jgodfrey
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Posted: 29 June 2022 at 9:59am |
It was hot tanked this time when I had it rebuilt, but not the time my dad had it done back in the 80's. Then it wasn't a full rebuild - just bored over with new pistons, etc. I remember going to the shop and seeing it when I was a kid. It was on an engine stand with no head. The block was clean, but still painted. Granted, it had more paint on it than in my picture above. I know this is sort of a tangent to my post, but I went back and looked at more pictures of my teardown and it looks like it was painted sort of a red\orange. Which sounds like a factory rebuild color. Which might make sense if it was from a 3A - explaining the timing gear cover and the backwards motor mount. Here is a shot of that. There is a farmer fix to make the reverse mount fit. Pretty interesting to try to do the forensics on what kind of life this thing lead. Clearly it worked for a living, then I beat on it in the woods for 15 years. Now it is retired...  |
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Michaeltru
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Posted: 29 June 2022 at 10:33am |
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Your new distributor that doesn’t fit— you dropped it in with the cap on? If I’m reading correctly? Did you drop it in with cap off and rotor on? Then turn the rotor to see if it will drop into the slot?
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Mike in AZ
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jgodfrey
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Posted: 29 June 2022 at 11:25am |
Initially I dropped it in with the cap on after aligning it visually to the slot. Then I realized my mistake and pulled the cap and rotor off. I could feel that it wasn't even touching the slot. That's when I realized the shaft was not in all the way.
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Michaeltru
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Posted: 29 June 2022 at 11:29am |
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Thanks
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Mike in AZ
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Joe DeYoung wrote: