M38 : OK, Boomer

Naugha · Post by **Naugha** » Sun Mar 27, 2022 7:07 pm

Replaced the shorter belts (4551511A1155) with .5" longer belts (Dayco 15460 11A1170) which gave me enough clearance for the canister. The shorter belts would be perfect for a cuno with the generator snug up to the indentation in the oil dipstick tube but the longer belts solved the problem and I can always opt out for a cuno or a Junior later. It's the can that came with the jeep and I think it looks good.

Guys, let me know if you see mistakes... especially big functional ones .... does anything go in those bottom plate holes ?

Did not add the indicator part mentioned by Ron .... did not see where it would attach to the timing cover... just a bump there.

RonD2 · Post by **RonD2** » Sun Mar 27, 2022 8:12 pm

Naugha wrote:Guys, let me know if you see mistakes... especially big functional ones .... does anything go in those bottom plate holes ?

Hi Don,
Check out Figures 32 (page 41) and 77 (page 93) of your TM9-1804A M38 Engine Manual.
Can also be seen in Figures 01-1 and 01-2 on pages 11-12 of the ORD9 manual.
There's supposed to be studs in those holes with nuts that hold the front engine plate to the block.
Studs are listed in the ORD9.

Here's a photo where the timing indicator pointer is bolted to the timing cover under two of it's nuts. Hope it helps.

No big deal, but if it matters, you have what I believe is a MB/GPW or CJ crankshaft pulley nut made for the manual (hand) starting wrench. It wasn't used on the M38.

Post by **wesk** » Sun Mar 27, 2022 9:43 pm

Original raised timing marks (also note the one lower left stud & nut for the front mount plate)

Later M38A1 timing pointer

4x4M38 · Post by **4x4M38** » Mon Mar 28, 2022 7:01 am

Don,
If that “Greek” trailer harness as you call it was bought from Brent Mullins off eBay it is actually the rear light harness for the jeep, not a trailer harness.

The two plug light switch split the front and rear light wiring. What you have goes in the one plug and provides the wiring for all the real lights including to the trailer harness plug.

Having that might make turn signals a little easier.

Also, newer M35 harnesses can be had in much better condition. Can supply details. They are not inexpensive but a lot less expensive than a new M38 harness. And the five wire semi trailer wiring harness on eBay is also a good buy for supplies.

4x4M38 · Post by **4x4M38** » Mon Mar 28, 2022 7:06 am

https://www.ebay.com/itm/171257498909

Remember, the trailer plug on the jeep has pigtails and connectors that attach to the light harness.

The actual trailer harness has two plugs on it. One to go in the socket on the jeep and one to go in the socket on the trailer.

RonD2 · Post by **RonD2** » Mon Mar 28, 2022 7:53 am

Some NOS M35 harnesses are getting long in the tooth.
I've seen package dates and wires date marked 30+ years old.
Caveat Emptor.

RonD2 · Post by **RonD2** » Mon Mar 28, 2022 8:10 am

Don,
I could be mistaken, but your grounding strap in this photo looks painted and I don't see a star lock-washer on it.
Might want to address that now.
Ground connections have to be bare metal to bare metal with star lock washers or you risk electrical malfunctions later.
Paint them after making the connection.
I bolt my strap to the back side of the plate to help protect it a bit better.

Naugha · Post by **Naugha** » Mon Mar 28, 2022 8:15 am

“There's supposed to be studs in those holes with nuts that hold the front engine plate to the block. Studs are listed in the ORD9.” Ron

Ron. Here is what I see. Need clarification.

ORD 9 SNL G-740 / P.16 / Fig. 01-5 Cylinder Block
M/Bolt/ 122119 and N/washer/ 138489

M&N appear twice in the diagram and appear to hold L (the plate).
When I do a pdf search of ORD 9 for ‘122119’ I find:
Bolt, machine, blah,blah ..... 3/8-16NC- 3x 3/4
Then the washer that goes with it...

* Are M&N the parts needed?
* Can whatever goes in those holes be addeded without taking off the plate?

oops... just noticed Wes pic showing studs in those two holes.

So.....what studs ??? Can’t find ‘em. Can I put them on without taking off the plate??

Wes. Are your timing mark pics telling us that my M38 timing cover does not use a pointer ???

RonD2 · Post by **RonD2** » Mon Mar 28, 2022 8:50 am

Don,
Yes, whether you use bolts or studs with nuts, you should be able to easily install them without removing the plate. After all, it was made that way.

I could be wrong, but believe there's some confusion in the ORD9 about bolts or studs with nuts in those holes.
Every illustration I see in the manual shows studs with nuts. Both my engines use studs with nuts in those holes.
If you look closely at Figure 01-5 on page 16 in the ORD9 it shows a stud in the hole.

That said, look at ORD9 page 41 under the timing cover and you'll see 4 bolts, 6 studs, and 10 nuts listed.
The problem with that is the timing cover only has 8 holes (not 10).
I'm pretty sure the Army inadvertently included the 2 studs for those holes with the timing cover instead of with the block or plate.

I'm not going to pull mine to measure them, but am reasonably certain that the timing cover stud listed on page 41 as Ord# 113247 is correct for those two holes.
Or use a 3/4-inch long bolt. Either with lock washer.

I noticed you used all bolts on your timing cover anyway, so having the correct by the book fastener may not be important to you so long as there's no functional loss.
My previous comment about your head stud lengths excepted.

I use the timing indicator pointer. I'm glad I do.

Naugha · Post by **Naugha** » Mon Mar 28, 2022 9:22 am

Thanks Ron. Guess I’ll use bolts.

I am almost sure that bolts were used by the last guy who dug into the engine and I followed what I saw without double checking the TM.

It’s all good as long as the front of the engine doesn’t fall off.

I think I will leave the WW2 crank shaft nut... Funny, I had the correct one on it but then thought the other big one was proper.

So... the pointer was a M38A1 thing?

The grounding surface for the strap is bare metal with paint only on the upper surface. I may go back and change over to a star washer.

RonD2 · Post by **RonD2** » Mon Mar 28, 2022 9:30 am

Without checking that ORD9, I believe the timing indicator pointer was factory installed on the M38A1. Wes will straighten me out if I yak out of school.

I haven't seen an Army-issued MWO or TB that installs it on the M38, but it's one of those common-sense additions that I bet happened in the motor pool anyway.

Page 55 in the M38 Reference Guide says it was used on the M38 "post production".
Good enough for me.

Post by **wesk** » Mon Mar 28, 2022 9:49 am

Wes. Are your timing mark pics telling us that my M38 timing cover does not use a pointer ???

Correct. The early M38 with the earlier 641087 casting used the timing window in the bell housing adapter plate and the timing marks were on the flywheel. The early M38 has no marks or tabs on it's timing cover. The late M38 with the advent of the later waterproof block (late 641087/804380) with the extra two rows of bolts in the rear flange used the timing cover with the raised markings.

RonD2 · Post by **RonD2** » Mon Mar 28, 2022 9:59 am

Hey Don,
While we're at the front of your uncovered engine and maybe using fasteners at hand rather than consulting the manual, I thought I'd mention this one:

Take a peek behind the crank pulley at the front oil pan bolts where they come through on top under the timing cover.
One of the bolts (if I remember correctly, 2nd from the right facing it) --- if it's too long it can dent or puncture the timing cover.

Naugha · Post by **Naugha** » Mon Mar 28, 2022 10:32 am

“My previous comment about your head stud lengths excepted.“ Ron

So Ron.
Is there a functional problem with the head studs that have nuts flush with the top of the stud? The oil canister bracket eats up some thread distance.

I bought studs that were ‘supposed’ to fit the M38 head including the two very long ones. I am bad about trusting too much in ad descriptions and not checking the manual.

Maybe the nuts can be torqued another thread or so ????
Maybe add some thread lock????

RonD2 · Post by **RonD2** » Mon Mar 28, 2022 11:04 am

Don,
There are 15 head studs, 12 "short" and 3 "long" (not 2), with lengths for each group specified in the ORD9.
The 3 "long" studs go under the engine lifting hook plate.

I can't see all of yours, but looking at the photos, your nutted studs show various amounts of threads above the nuts, some look like as many as 10 threads showing and some show none (flush with the top of the nut).
Without knowing what studs you bought or used and where you put them, it just raises questions to me whether the correct stud is in the correct hole.

Does it functionally matter? I suppose not if too long, but conventional mechanical wisdom says at least 2-3 threads ought to show above the nut on a properly torqued fastener to guarantee full thread engagement and proper torque holding power.
You can google the debate.

If you already torqued them to spec you shouldn't torque them any more to get more thread showing. Well, I suppose you could try but stand-by for bad stuff to happen.
Even after you run the motor up to temp for the first time and then re-torque them like called for, I don't think you'll get any more thread showing out of them.

Head studs and nuts are pretty important. I believe they should not only be done right, but they should look like they were done right.
When I look at yours I wonder.
Maybe they function, but they leap out as shade tree to me.
Just my 2-cent opinion.

The good news if you want to straighten them out is you can pull them one or two at a time with no need to yank the head or buy a new head gasket.
Just remember to re-seal the threads that go into the block and torque it up before moving on to the next.