M38 : OK, Boomer

[RonD2]

I'm a rookie. Never built a motor before in my life.
My motor is pickled and waiting for me to assemble it.
I had the machine shop install keenserts in all 15 stud holes.

Once I get a round tooit, I'm going to build it using these:
Quantity 15: https://www.armyjeepparts.com/p-3722-cy ... 38589.aspx
Quantity 3: https://www.armyjeepparts.com/p-215-cyl ... a1549.aspx
Quantity 12: https://www.armyjeepparts.com/p-216-cyl ... 49368.aspx

I'm going to set the 12 short studs just high enough to give me 2-3 threads showing above each nut.
Research tells me this is acceptable mechanical practice.
I figure it's one of those things (like Wes often says) that real mechanics know but you can't read in an Army manual.

What "diagram" are you referring to?
Yes, 7/8 = .875

If it helps:

[Naugha]

Went to a local auto parts warehouse and found this.
I was talking about the stud diagrams Wes posted a few panels back.

[RonD2]

Those look like they ought to do the trick.
Did you happen to get a brand name and part number for folks who might be interested?

[wesk]

Ron,

Not sure what industry standard info you are using. Beware unless it is based on original engineering drawings and reports from Willys you are treading on thin ice. To start with just turning the stud out a few turns to add the needed thread exposure above the nut is dangerous. I have not found an engineering order, or service bulletin/instruction that tells you to do that. Using common sense to sort out issues like this is less dangerous.

For example The current hardened steel 3 1/2" studs have 9 1/2 course threads. The block has 8 1/2 cast iron threads. If you fully seat the stud you will have 1 thread in the anti-freeze. Here is where the smart technician chooses risk levels wisely. He assumes the engineer put 8 threads in the cast iron block so they would provide adequate thread engagement and strength. The more of the cast iron threads you leave unfilled with hardened steel stud results in a weak thread engagement which can and usually does lead to failure of the cast iron threads when torqueing and re-torqueing the stud nuts. You should re-think your approach to thread engagement!

[wesk]

Don,

You said "

I see a listing for “WO-A1549 (3 7/8”) studs.”
Is that the three long ones?

The diagram shows WO-A1548 as 3.875”.
Are WO-A2548 and WO-A1549 about the same stud?

About how many more threads on a WO-A1548 or WO-A1549 than the 3.5” stud.

1st. I assume your fist sentence should say WO-1548 instead of WO-2548?

The WO A1548 studs are for the WWII MB/GPW's and are actually listed in the G503 ORD 9 as " Stud, S, cd or zn-pltd, 7/16-14NC x 7/16-20NF x 3 7/8.

The WO-1549 studs are for the WWII MB/GPW's and are actually listed in the G503 ORD 9 as " Stud, S, cd or zn-pltd, 7/16-14NC x 7/16-20NF x 3 7/16.

One would need a copy of the applicable part number stud's engineering drawings from Willys to accurately post what could be considered accurate individual thread lengths and counts.

As I just posted above the safest course is to set the old (already crushed) gasket on the block then install two of your 3 1/2" studs until they bottom out in the block. Now set the head on the gasket. Now install and torque two stock correct part number nuts and torque them. Now determine if you have 1 1/2 threads above the nut? If the answer is no then determine the extra length of fine threads you need to get the needed 1 1/2 threads showing above the nut.

In your next post you said: "

Went to a local auto parts warehouse and found this

Are those at least Grade 8 automotive hardwaree?

[RonD2]

Thanks Wes,
Wow. That pretty much means that several editions of the ORD9's (G740, G503), the stud measurement sketch you posted, and the vendors (MWM, AJP, etc) who sell 3-1/2 inch studs advertised as correct are all wrong?
Not including 15+ years of posts in this forum and it never surfaced before today?

I don't want to de-rail Don's project thread so I'll open a thread in the Technical Knowledge Base forum.

[Naugha]

Here are the Summit Racing data on the studs.

https://www.summitracing.com/parts/rnb- ... gLt3PD_BwE

The 675-013 is two threads longer than the 3.5” studs plus there is no noticeable top shoulder on the 675-013 as one finds on the 3.5” studs.

The overall appearance is that you get three more threads on the 675-013. Can tell more when I insert the new studs. We shall see. The auto warehouse is humongous. They may have even longer studs if needed.

I made the WO-1548 correction mentioned above.

[Naugha]

I only know what I read in the funny papers and have way too much faith in G503 / Kaiser Willys videos.... gosh, the name contains ‘Willys’. How could they be wrong?

Not sure why my 3.5” studs were too short, but here is (I think) a very wrong video that may have influenced my reassembly of the head. Take a look.

Are these guys way off when they put a torque wrench to the L134 head studs? I may have watched that video and snugged those studs past finger tight and lost a thread or two...... really can’t remember. The studs are now easy to remove so maybe I didn’t use Magnum Force. Anyway....

https://youtu.be/Vu_e4oaLO1E

[jake138]

With a perfect stud in a perfect thread hole, the first 6 threads are doing almost all of the work:

http://www.gizmology.net/nutsbolts.htm

Not withstanding further discussion on the thread percentage or the quality of those first 6 threads in Don's block and unknown torques and retorques, I would have to say that if backing out the studs from the bottom of their threaded holes one revolution weakens the threads to the point where they strip out of the block, then those holes would have needed Helicoils anyways.

One extra thread should not be the breaking point of threaded hole, and if it is, that means the first seven threads were already too far worn to be trusted anyways.

The article I linked also discusses the fact that the threads left above a nut are due to the first threads on a stud being improperly formed. The article also states that the average fine threaded nut has 8 threads, which means that by the rule stated that the first 6 threads do most of the work, the last two threads in the nut are not contributing much clamping force, and that by leaving the nut flush with the end of the fine thread on the stud, you are not sacrificing any strength.

[Naugha]

Hi Jake.

So,

If ‘finger tight’ takes me to the bottom of my stud hole and the longer shaft on the studs I just bought (see pic) gives me three fine threads above the nut.... and I use a Permatex #2 , a new head gasket, and proper torque on the nuts....

then I can declare victory and get on with whatever I was about to do?

What the heck was I doing? Something about a jeep. Not sure. It’s all a blur.

[jake138]

In my unprofessional, unorthodox, inexperienced and unasked for opinion, yes you should raise your victory flag and crack a cold one to celebrate

[wesk]

Don,

You said:

Here are the Summit Racing data on the studs.

https://www.summitracing.com/parts/rnb- ... gLt3PD_BwE

The 675-013 is two threads longer than the 3.5” studs plus there is no noticeable top shoulder on the 675-013 as one finds on the 3.5” studs.

The overall appearance is that you get three more threads on the 675-013. Can tell more when I insert the new studs. We shall see. The auto warehouse is humongous. They may have even longer studs if needed.

Yes they are grade 8 and should work just fine.

I only know what I read in the funny papers and have way too much faith in G503 / Kaiser Willys videos.... gosh, the name contains ‘Willys’. How could they be wrong? Shocked

Not sure why my 3.5” studs were too short, but here is (I think) a very wrong video that may have influenced my reassembly of the head. Take a look.

Are these guys way off when they put a torque wrench to the L134 head studs? I may have watched that video and snugged those studs past finger tight and lost a thread or two...... really can’t remember. The studs are now easy to remove so maybe I didn’t use Magnum Force. Anyway....

I watched that video several times and I could not be sure that there was a torque wrench used on the studs or was that just a long handle ratchet? I saw nor heard no reference torque value for those studs in that video.

[wesk]

Jake,

In your post above you said:

With a perfect stud in a perfect thread hole, the first 6 threads are doing almost all of the work:

http://www.gizmology.net/nutsbolts.htm

Not withstanding further discussion on the thread percentage or the quality of those first 6 threads in Don's block and unknown torques and retorques, I would have to say that if backing out the studs from the bottom of their threaded holes one revolution weakens the threads to the point where they strip out of the block, then those holes would have needed Helicoils anyways.

One extra thread should not be the breaking point of threaded hole, and if it is, that means the first seven threads were already too far worn to be trusted anyways.

The article I linked also discusses the fact that the threads left above a nut are due to the first threads on a stud being improperly formed. The article also states that the average fine threaded nut has 8 threads, which means that by the rule stated that the first 6 threads do most of the work, the last two threads in the nut are not contributing much clamping force, and that by leaving the nut flush with the end of the fine thread on the stud, you are not sacrificing any strength.

I read gizmo's article as well and the ration of 6 threads doing most of the work on an 8 thread nut was while referring to fine threads 7/16x20NF. And he also noted that the other two threads still did a smaller portion of the work. He also stated the first two threads are considered not standard or up to the task and this is common with studs when the ends of the stud have a very slight taper making the last two threads unreliable. based on his observations and interpretations you don not want those last 2 threads carrying any of the load. All of his discussions were directed at the fine thread end of the stub but common sense dictates they can be applied just as well to the course threads on the other end but he did not offer the stress specs for the 7/16x14NC threads which again common sense says the first two threads at the tip are unreliable and should not be relied on to fulfill the stress requirements.

In Don's post he said the top of his original 3 1/2" studs were flush with the top of the nuts. So one turn does not give him the standard 1 1/2 to two threads above that we are use to maintaining.

[Pierre]

Just wondering if head gaskets sold today have the same thickness as those used by willys at the factory back in the day...Does anybody have a NOS gasket to compare with modern ones?? Don't think it would make any difference but just asking

[Naugha]

Another problem I had when attaching the head (the first time) :

The head gasket I got from an ebay vintage jeep vendor had no markings indicating up/down, no instructions and no brand markings.

There are threads out there that discuss other ways to determine the gasket orientation but this time around I will buy a more idiot proof gasket with clear installation markings.

“Yo, noob.... point this side up toward the sky. Note that my other side will be touching the block. Have a nice day.”