M38A1 Distributor and Plug Wire Question

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
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M38A1 MP Jeep
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M38A1 Distributor and Plug Wire Question

Post by M38A1 MP Jeep » Thu Oct 12, 2006 8:21 am

I have my engine lined up at the 5 degree BTDC mark. The rotor inside my 24 volt distributor is facing the 7 o'clock position.

Looking at my distributor with the cover placed back on, is this the correct assumption:

1st cylinder - 7 o'clock position
2nd cylinder - 5 o'clock position
3rd cylinder - 1 o'clock posiition
4th cylinder - 11 o'clock position

I know the firing order 1342 CCW.

I also know the plugs go from 1st cylinder at the front of the engine block back to #4 near the firewall.

If my assumption is correct, then all I have to do is match up the wiring coming from the cylinder location on the block to the corresponding location on the distributor based on the firing order above?

I am a little thrown off because my rotor pointed to a different location within the 12 volt distributor I just removed and replaced with the 24 volt one.

Thanks...

Jon
I am seeking information on M38A1's configured for MP use from 1953-?.

I am also interested in equipment and uniforms worn and carried by MP's during this timeframe.


Wes K
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Post by Wes K » Thu Oct 12, 2006 8:32 am

The civilian and military distributors are clocked differently due to their shape vs travel requirements when adjusting. If you use the complete setup data I sent you some time back starting with the correct clocking of the oil pump then just follow the steps and #1 should end up at

Image

What you suggest will work but may restrict your ability to swing the distributor housing enough to time it correctly. But you must be absolutely sure that #1 piston is top on compression and in the 5 deg BTDC firing position before you select the location for plug wire #1. You do this by having a buddy turn the engine over by hand using eith pressure on the fan belts while turning the fan in the nprmal direction of crank rotation or using a socket and ratchet on the crank nut. When you fell air pressure trying to blow your finger off the plug hole watch the timing marks and slowly continue rotating untill your 5 deg BTC mark is lined up.
Wes K
45 MB, 51 M38, 60 CJ3B, 60 CJ5, 76 DJ5D, Bantam T3-C MVPA22099

M38A1 MP Jeep
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Post by M38A1 MP Jeep » Thu Oct 12, 2006 8:46 am

Wes

That picture is exactly how it looks. The finger over the cylinder hole trick works great, you shared it with me when I did the 12 volt timing and it worked perfectly. The engine ran great.

There are two bolts on the back of the distributor. one locks the whole distributor to the block. The other is the one loosened to swing the distributor to time it correctly.

With the first bolt holding the distro to the block, at what position should the distributor be swung too if the bolt on the back of the distro is loosened - towards the firewall, all the way down towards the radiator, or somewhere in between? Or, if my distro is locked down with the rotor pointed to 7 o'clock and looking like your attached picture, am I at a good starting point assuming I have the 5 degree BTC set as discussed already?

Thanks again...

Jon
I am seeking information on M38A1's configured for MP use from 1953-?.

I am also interested in equipment and uniforms worn and carried by MP's during this timeframe.

Wes K
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Post by Wes K » Thu Oct 12, 2006 11:05 am

If you are 5 deg BTC on the timing marks, and the rotor is poiting as indicated with the distributor body positioned as indicated you should be with a couple degrees of dead on.

Image
Wes K
45 MB, 51 M38, 60 CJ3B, 60 CJ5, 76 DJ5D, Bantam T3-C MVPA22099

Maverick1701
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Re:

Post by Maverick1701 » Tue Dec 07, 2021 4:53 pm

Wes K wrote:
Thu Oct 12, 2006 8:32 am
The civilian and military distributors are clocked differently due to their shape vs travel requirements when adjusting. If you use the complete setup data I sent you some time back starting with the correct clocking of the oil pump then just follow the steps and #1 should end up at

Image

What you suggest will work but may restrict your ability to swing the distributor housing enough to time it correctly. But you must be absolutely sure that #1 piston is top on compression and in the 5 deg BTDC firing position before you select the location for plug wire #1. You do this by having a buddy turn the engine over by hand using eith pressure on the fan belts while turning the fan in the nprmal direction of crank rotation or using a socket and ratchet on the crank nut. When you fell air pressure trying to blow your finger off the plug hole watch the timing marks and slowly continue rotating untill your 5 deg BTC mark is lined up.
Wes are you still a member here? Would you mind sending me that same setup data? I'm doing the same thing (military distributor on a civ motor)
Chris
1954 M38A1

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dpcd67
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Re: M38A1 Distributor and Plug Wire Question

Post by dpcd67 » Wed Dec 08, 2021 6:36 am

This thread is decades old by now; probably should PM him......just a suggestion. People tend not to read these.
Contact him on M series web site.
U. S. Army 28 years.
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Cuz
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Re: M38A1 Distributor and Plug Wire Question

Post by Cuz » Wed Dec 08, 2021 11:05 am

Here's the link to my photo album Ignition Timing

http://www.willysmjeeps.com/v2/modules. ... _album.php

Image
Distributor shaft to oil pump shaft indexing must be done first.

Image
This is the corrected plug wire indexing in the cap for those using the M38A1 manual references.
Cuz (AKA Wes K)
45 MB, 51 M38, 54 M37, 6? M101A1, 60 CJ5, 76 DJ5D & 47 T3-C


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