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The Head Stud Blues

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Carlsjeep View Drop Down
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    Posted: 21 July 2012 at 3:40am
I covered the cyl bores and did a three angle seat grind, checked the valves for contact, assembled the springs and adjusted the valves yesterday. Today figured out how to time the lube pump so the distributor rotor is where I want it. Then I installed the head studs, sprayed the head gasket, put the gsk and head on and started torquing the nuts. I got to 60 ft lb and was almost through the pattern and  Shocked one of the stud threads went soft.  Cry ohhh that sick feeling I have had before when this happens. 

I pulled the head, the gasket, the studs and cleaned the head and deck up, called Walcks and ordered 15 studs and nuts, called MSC and ordered 6 Keensert inserts. Tomorrow I will order another Victor 1023K head gasket and do a torque test on each head stud thread in the block to find any others that may fail. To be honest I was tempted to do that before I put the head on but thought, they all look good and I removed the studs from them when I had the block cleaned and checked. I should have listened to my inner feeling, something always goes wrong when I don't.

Well, I have a lot of things to do to it while waiting for the parts.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote OverlandMan Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 2:12am
That's too bad Carl. I hate that feeling too. Sounds like you got a good plan though. Good luck!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rocketeer Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 12:23pm
Carl I hope you didn't run a thread chaser down those holes. One of the leading causes of thread pull is using a thread chaser. When you repair it check to make sure the area around the hole is still flat. Pulling a thread usually results in a slight bump around the hole which generally causes a head gasket problem.

Larry
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hillbilly21 Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 12:39pm
 WORDS OF WISDOM..TORQUE TO 45-50 THEN GO AROUND AND RUN IT UP TO 60 THEN GO BACK AND RE-TORQUE TO MANUFACTURES 70 LB..

POINT BEING THIS WILL KEEP EVERYTHING ON AN EVEN KEEL . I HAVE EVEN TORQUED THEM TO 50 THEN PUT ALL BACK TOGETHER RAN IT TILL HOT THEN WENT TO THE 70 AS RECOMMENDED Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Carlsjeep Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 3:40pm
I can't agree with not running a tap through the bolt holes to clean them out. It's an accepted and recommended practice in the automotive industry. The fact that you can't get a true torque unless the thread is clean requires that the threaded holes be cleaned with a tap and the bolts with a die. There is no other way to insure clean threads and a true torque. The tap does not damage the thread if it is a solid thread, if the threaded hole has been over torqued or the metal has fatigue it will not hold full torque of the rated thread size and it's not the fault of having a tap run through the hole. One thing that will happen though is when you run a tap through a hole with stressed threads it will make the thread weaker but the weakness was already there to start with and not the fault of running the tap through it.

With dirty threads, male and female mating threads will not reach full torque even though the torque wrench clicks or the dial shows the value your torquing to. The dirt causes friction that will stop the bolt from turning before it reaches true torque value. Cummins required mechanics to clean the head bolt holes and head bolts and lube them before installation and other manufacturers did as well. 

Another issue is rough finish on the threads. If the bolt or stud has a rough finish it is recommended to discard the bolt or stud or nut and if the bolt hole threads have a rough finish it's recommended to install an insert. Even a clean thread with a rough finish will not torque to correct value and in fact the thread will lock up on a nut or in a threaded hole and the threads will distort and fail.

Even bolt manufacturers tell you to clean the threads before assembly to achieve full torque. If you don't clean the threads you can expect the head to not be torqued correctly and the gasket will not be sealed properly. Plus, no two bolts will be torqued to the same value and that may lead to head and block warping and head gasket leakage.

I have to admit that I failed to follow the very things I was taught years ago. A couple of the studs had rough fine threads after cleaning them up. I looked at them and thought I could get by with using them. WRONG, it was those very two studs that the nut locked up on the stud and pulled the thread in the block. When I removed the two studs from the block I had to use a vise and wrench to loosen the nut on the stud. 

When your working for a living as a mechanic and you or the company you work for has to warranty your work you don't take chances or short cuts, at least you shouldn't if you want to build a good reputation. Cummins, Detroit and Caterpillar didn't like or want comebacks from head bolt or bolt hole failures and were adamant about cleaning and replacing damaged threads at distributor shops. The dealers did not always have as high requirements and had to pay for their own comebacks but the manufactures did not want to see thread failures because of poor workmanship and wouldn't pay for it.

I was the Warranty Administrator and Training Manager at Cummins at one point in my career and know full well the issues we are talking about right now doing training of mechanics and handling dealer and distributor warranties.

EDIT: Cummins required you to torque the heads mains and rods to the full spec torque and after the dyno run you allowed the engine to cool and rechecked the head bolt torque. You did not check the mains and rods. If you don't torque the head bolts to the required torque the head gasket may not seal and you should never torque a bolt while it is hot. When you do that and the engine cools the bolt will be over torqued and possibly end up stretched when everything cools and it will not be torqued to the spec.  

 


Edited by Carlsjeep - 22 July 2012 at 3:53pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rocketeer Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 4:25pm
Originally posted by Carlsjeep Carlsjeep wrote:

I can't agree with not running a tap through the bolt holes to clean them out. It's an accepted and recommended practice in the automotive industry.

Not on these L-134's it isn't. Forget what diesels require, it's a known fact that running a tap down the hole on these L-134's cleans out more than dirt, it opens up the thread a small amount (due to the way the factory cut them), just enough to weaken them and make them susceptible to pulling when torqueing.

Larry
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Carlsjeep Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 5:13pm
Larry, you can't weaken the thread by running a tap through it unless the thread has already been stressed and the base metal pulled and fractured. A tap only cuts to the original dimensions of the V form. The V form thread we have now is the same V form that has been in use since before WWII. A 7/16"-14 tap made in 1940 will have the same exact dimensions that a 7/16"-14 tap made today, nothing there has changed.

Now, if Willys used worn out taps to thread the holes, and during war time it could happen, then the only change would be the depth of the V and that equates to what is called in a female thread the major diameter. From what I am reading many have run a tap through the holes and the thread in that hole had already been stressed to failure. When you run a tap through a thread like that your not creating a failure, your just making it worse and it will fail at a much lower torque value. If the thread is already stressed it will fail anyway when you try to use it whether you ran a tap through it or not.

These blocks are probably not the best cast iron to start with so they are prone to failure from the start. That and the fact they were mass produced under war time fast production requirements adds to that failure rate. Add to that they have been abused over the years by shade tree mechanics hasn't helped at all. An untrained mechanic is not good for engine life. At some point in time better cast iron was used in engines by all manufacturers and they quit using studs. 

There is one forgiving factor with studs. You screw a stud in by hand and snug it down lightly and then the nut is used to torque the head. This lets the threaded stud in the block remain stationary and that will help thread life in weak cast iron and let all the turning stress be on the nut and stud. What is probably happening is some people tighten the studs to much and stress the thread in the block and that is not good and some blocks are just weak and prone to failure. Another block thread failure is caused by what I did, using a bad stud and/or nut and it locks up and pulls the thread out of the block. 

I am bluntly telling everyone you probably are your worst enemy by using bad studs and nuts and any rough nut or stud thread can and will cause thread failure. I made that mistake and I am paying for it now and it's NOT because I ran a tap through the block thread.

I am putting this information out for anyone who wants to know the truth about threads and thread life/condition. I am not telling anyone they HAVE TO DO IT THIS WAY, I'm telling facts. What anyone wants to believe or use is up to them and I suggest they buy some machinist books and check with bolt manufactures for data. The more information you have the better you are.


Edited by Carlsjeep - 22 July 2012 at 5:19pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote F Bill Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 6:17pm
There is a difference between the thread chaser sets and normal taps...and lots of the cheaper taps seem to recut threads beyond the class of fit needed, in my experience...
 
My taps  and dies, even though they are US made Hansons, seem to always cut more than I want them to, dry or not, slow or not, backing off the tap every 1/4 turn or not.. I guess I need to find some better ones?..Perhaps being over 20 years old might be the issue....Shoulda seen the threads I cut on some rod stock remaking the radiator support rods...Yeccch!.
 
It sure seems that head bolt threads are often a source of frustration on our jeep engines. I have a lot of parts engines in stock with bad threads, cracks starting at the head bolt holes, or even missing cast iron pieces at the holes... 
If you haven't checked out the tech FAQ section, go to:
http://www.thecj2apage.com/forums/tech-faq_forum57.html
for a lot of great stuff you need to know!!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Carlsjeep Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 6:53pm
Bill, I'm sorry that I may have misunderstood what you meant. I totally agree that the thread chaser types are not a good choice at all. When I was working for a living I bought quality HSS taps and fixed HSS hex dies to clean and chase threads with. I still have them in a box and use them all the time but I DON'T use them to cut a new thread, it would ruin them for chansing threads. A person should buy a quality HSS tap and fixed (not adjustable) die to do this job. It's hard to find a HSS tap or die in hardware stores. 

Hanson taps and dies are carbon steel and do hot hold up well. What will happen is they are hard and fragile and the tips where the cutting occurs will break or wear and that will cause it to cut a deformed thread whether your chasing a thread or cutting a new thread. Look closely at the leading tapered end of the tap for wear or chipping and discard that tap if it's damaged. That is where most of the thread cutting is happening and the rest of the thread down the side of the tap is just chasing the thread started by the leading end. I have tried to sharpen a tap and it has not worked well most the time so I just throw it in the scrap metal bin. 

I do a lot of power tapping and a dull tap will break and I don't like to remove broken taps. It's true, these blocks are a real source of trouble. I am going to make a sleeve so I can torque test each stud hole using a stud and nut and I will post the dimensions here so anyone that wants to can copy it. I think to save a person from having to pull a head because the block thread failed they may want to do this torque test on each hole unless they KNOW their stud holes are ok. 

Talk about frustration, I have experienced it with my original block having a crack develop between #3 intake valve seat and the #3 bore. Then my replacement block having slight cracks between the center water passage and the two stud holes beside it. Both I and the engine machine shop believe it will be ok. OTOH, I am going to clean and magnaflux my original block and repair if if nothing worse is found. I am seriously considering putting inserts in those two holes to satisfy my mind. 

I don't think anyone should throw away a block that could be repaired and used by themselves or someone else. There is a limited supply out there and as time goes by we may wish we kept that block we thought was scrap. Almost anything can be repaired when there are none left to use.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hoosierhiker33 Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 7:02pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bkreutz Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 8:50pm
Originally posted by rocketeer rocketeer wrote:

Originally posted by Carlsjeep Carlsjeep wrote:

I can't agree with not running a tap through the bolt holes to clean them out. It's an accepted and recommended practice in the automotive industry.

Not on these L-134's it isn't. Forget what diesels require, it's a known fact that running a tap down the hole on these L-134's cleans out more than dirt, it opens up the thread a small amount (due to the way the factory cut them), just enough to weaken them and make them susceptible to pulling when torqueing.

Larry


Larry, now you know why I stopped posting any answers to questions, not worth the effort or the argument.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Carlsjeep Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 9:36pm
I am not doing this for those with a closed mind. It's information and you can take it or leave it. 40+ years as a mechanic and machinist with an open and searching mind has taught me everyone has something to contribute and if you don't like or believe something keep doing what your doing.

bkreutz, this thread was not started as a question, it is about something that happened and I wanted to post about. That is what this site is about isn't it? I didn't know you had to be a Jeep expert to post things here.  Just because I haven't worked on CJ's for most my life doesn't mean I don't know something about engines. I'm sorry if you think I should have years of Jeep experience to discuss my experience with my Jeep but I can live with it if you can.  

I made the sleeve and used a like new original stud I have and a new nut. The sleeve is 2.200" long to replicate the approximate height of the head and gasket. 


I tested each stud hole to 60 ft lb with the stud thread and nut oiled. That would make the actual torque a little over 65 ft lb because if you oil the threads you have to reduce the torque by 10%. When I got to the stud hole where the device is mounted in the photo it torqued to the 60 ft lb with no problem and that is the hole that I thought was stripped. So I increased the torque to 65 ft lb which would give 70 ft lb and it still held firmly. All the holes in the block pulled to an actual torque of 65 ft lb by using the setting of 60 ft lb and an oiled thread.

So the only thing I can figure that happened is the thread in the nut and stud gave up and the thread in the block held. When the thread failed I stopped turning so it's hard to see any damage on the stud or in the nut. I was taking a chance using the old studs and nuts anyway and had that stud not given up they would still be in there. The next time I would have had to replace the head gasket I would have had trouble with that stud at least.

As I said in an earlier post, if the studs and/or nuts threads look rough just replace all of them and be done with it. When the new head gasket and studs and nuts come in the head goes on without inserts.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Carlsjeep Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 9:38pm
Hoosierhiker33, why do you ask that when my location is on each post?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote I got the Willys Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 10:19pm
 Damn old engines, stuff just happens sometimes.Interesting jig to test the studs.The flattie in my 47 has bolts instead of studs.The engine has a manufacturers rebuild tag on the  and one of those temperature buttons epoxied on the block.
  The best pro engine builders always say to clean  threads with the best tap you can buy,not a thread chaser.
 Looks like all the precautions were taken ..but stuff does happen. Hopefully Walck's studs are quality stuff. 
 


Edited by I got the Willys - 22 July 2012 at 10:20pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rocketeer Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 11:16pm
Originally posted by bkreutz bkreutz wrote:

Originally posted by rocketeer rocketeer wrote:

Originally posted by Carlsjeep Carlsjeep wrote:

I can't agree with not running a tap through the bolt holes to clean them out. It's an accepted and recommended practice in the automotive industry.

Not on these L-134's it isn't. Forget what diesels require, it's a known fact that running a tap down the hole on these L-134's cleans out more than dirt, it opens up the thread a small amount (due to the way the factory cut them), just enough to weaken them and make them susceptible to pulling when torqueing.

Larry


Larry, now you know why I stopped posting any answers to questions, not worth the effort or the argument.

Yeah, I'm getting there. Some people simply won't listen to good advice based on years of experience with these engines and engines like them. Years of experience on diesels has only limited transference. I know for a fact that this problem can be caused by using thread chasers. It appears a thread chaser was used and the problem has arisen. What a surprise. Others reading this post can decide for themselves, listen to the advice I offered or listen to the guy who knows better and now has a pulled thread. No skin off my nose. Over and out.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote I got the Willys Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 11:34pm
  This is the internet,everyone is an expert ,just ask them. Big smile No matter what what is ,brain surgery to septic tank pumping,There's always differing opinions  based on personal experience
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Harveynailbanger Quote  Post ReplyReply Direct Link To This Post Posted: 22 July 2012 at 11:38pm
ok to those that know. im not trying to stir a pot. but i am at the point where im getting ready to assemble mine. what is the best way to chase or clean these threads if not a chaser or tap? (there in lies part of the misunderstanding above) should i just use a clean head bolt?  PM me if you dont feel comfortable with a public reply. but i have one block and its 60 over now so w/o lots of work i have 1 shot at this.
(I've assembled many engines and was taught to always chase the threads with cutting fluid or lt wt lube, then clean with solvent and install bolt or stud dry.)
Rick
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Carlsjeep Quote  Post ReplyReply Direct Link To This Post Posted: 23 July 2012 at 12:58am
Rocketeer, in every post I have said I used a HSS quality tap NOT a thread chaser and I also said I agree with you that thread chasers are not the right tool to use.

Rick, yes, you were told right, use a good quality HSS (high speed steel) tap and a light oil or kerosene and then blow the thread hole out to remove the loose dirt and rust.

It's like Larry and I said, the common thread chasers are not a good idea to use. 


Edited by Carlsjeep - 23 July 2012 at 1:07am
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