M38 Distributor

horse · Posted: Sat Apr 25, 2020 6:52 am Post subject: M38 Distributor

Just bought my first timing light.

So I made up a lead with a std plug and took a reading which suggested the timing is out a little.

TM 9-8012. After I have checked the points which had closed a little I moved onto the distributor. I see looking underneath there is a brass screw, a fixed bolt and a bolt in an adjustable slot.

The manual says to loosen the mounting clamp screw under the distributor and turn the unit until the timing marks appear together, then tighten the screw.

Question.Which do you have to loosen to allow the unit to move and adjust? The one in the slot looks most likely.

Did not want to jump in with both feet on this one!
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1952 M38

horse · Posted: Sun Apr 26, 2020 5:01 am Post subject:

Just found a nice photo by Wes 12-2006 to show the adjuster bolt only needs to be loose to make the adjustment. Its all there if you look.
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1952 M38

horse · Posted: Mon Apr 27, 2020 10:28 am Post subject:

Managed with the timing light to set it on 5 Degrees before TDC but its very close to full adjustment on the distributor slot.

It would be interesting to know how far along the slot the adjusting bolt normally sits, you would have thought somewhere in the middle so you can adjust either way. Unless I need the oil pump timing !
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1952 M38

wesk · Posted: Mon Apr 27, 2020 12:07 pm Post subject:

When you have a near contact or actual contact issue between the military distributor housing and the block it is caused by the uninformed individual that installed that distributor without following the manual instructions to first get the oil pump orientation correct before installing the distributor. The oil pump drives the distributor shaft. This is all covered in the appropriate manuals and in my photo album.

http://www.willysmjeeps.com/v2/modules.php?set_albumName=album119&op=modload&name=gallery&file=index&include=view_album.php

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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

horse · Posted: Mon Apr 27, 2020 3:52 pm Post subject:

Thanks, I had seen all the work you had put in and thought that might be the case.

Even though I have got the correct timing marks with the light when running would you still change the orientation of the oil pump?

So the distributor would end in the middle area of the adjuster or close.
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1952 M38

wesk · Posted: Mon Apr 27, 2020 7:18 pm Post subject:

As long as I can reach my target timing setting I would leave it alone. Are you aware there are two more ways to check timing. One is static timing and two is checking dwell with a dwell meter.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

horse · Posted: Tue Apr 28, 2020 1:10 am Post subject:

Hi,I have seen the one you posted pulling the paper from the points as they open to get the timing at 5 BTC but will look into the Dwell. I think I have a old meter which had a Dwell scale. Both good to cross check my results.
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1952 M38

wesk · Posted: Tue Apr 28, 2020 2:00 am Post subject:

Try to get your hands on the old military dwell meter/tach test sets.

You may find them at auctions hosted by US Military units that are tennents on RAF bases.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

horse · Posted: Tue Apr 28, 2020 2:13 am Post subject:

Nice bit of kit. How would yo use a Dwell meter on an M38 as the coil is enclosed and the instructions I have seen are for vehicles with easy to reach coils?
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1952 M38

horse · Posted: Tue Apr 28, 2020 2:45 am Post subject:

So bit more reading. Disi cap off plugs out. Dwell meter cable on positive side of coil and other cable to ground.

Turn engine over with starter and read the Dwell angle on the meter, for a 4 cylinder engine a reading of 60 would be in range. Adjust points as required.

Would that be close to the procedure?
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1952 M38

wesk · Posted: Tue Apr 28, 2020 10:07 am Post subject:

horse · Posted: Tue Apr 28, 2020 3:26 pm Post subject:

Thanks Wes looks like I could do with a bit more kit.
As its running okay I will leave well alone.

Thanks for the offer for the instructions, will keep looking at shows for this unit ,if one turns up when we get out of lockdown.
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1952 M38

rgmutchler · Posted: Tue Apr 28, 2020 6:01 pm Post subject:

I don't know the state of your M38, if you are putting it together after a frame off type rebuild, but if you don't have the generator on your engine yet you might want to check and make sure that the distributor won't interfere with it when you time the engine. Due to the size of the waterproof distributors the indexing of the oil pump and distributor can be critical in having enough room to turn the distributor to time it. Don't know if it applies in your case but just FYI.
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R G Mutchler
M274A5
M-38 MC13312
http://willysmjeeps.com/v2/modules.php?set_albumName=rgmutchler&op=modload&name=gallery&file=index&include=view_album.php

horse · Posted: Wed Apr 29, 2020 1:03 am Post subject:

Hi, thanks for the input. Yes it is all together, there was just enough room on the adjuster to give me the correct timing so I will leave it at that. In the future it is something I would like to check if any major parts need replacement.
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1952 M38

horse · Posted: Wed Apr 29, 2020 6:36 am Post subject:

Just on a finishing note with the adjusting slot being at one end anticlockwise .I had another look today with a tiny camera and found the distributor bolt adjuster is nicely in the middle of the arc, so pleased with that.

Once I have found out how to post photos with a Mac I will pop one up.
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1952 M38


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