Head Bolts Torque

tedder · **Joined:** Thu Sep 15, 2011 7:19 pm **Posts:** 137

Hi, I've been replacing rockers after rocker failure and took the head off to make sure nothing else was damaged. I decided to use OEM bolts just can't visualize spending the money for ARP bolts. I was torqueing the bolts and it seemed that some bolts torqued right down but others kept going and in one case I snapped one. I stopped and took out all the bolts and removed the head and to my surprise the bolt that snapped just came out by hand. I checked all the holes and all are clear. What is going on here?

I know I have a cheap torque wrench that could be the problem. So I have a better one on order.

But other than that what could it be?

I have heard that it takes 250 lb ft to snap one of the OEM bolts. When I took out the original they seemed like they were all about the same torque. This engine has never been over heated in fact there was barely any carbon on the pistons or valves and you can't even feel a lip at the top of the cylinder.

Now the question is do I buy all new bolts and gasket or can I just replace the one bolt and try again with my new torque wrench.

Any help is appreciated,

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

We have a bunch of head bolts if you need some or all. Take the mopar price and multiply by 0.7

DOC4444 · **Posted:** Wed Apr 02, 2014 8:27 am

Keith, do you suggest following the FSM procedure for tightening OEM headbolts or an alternate method as some others have suggested?

DOC

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

For the stock head bolts, I can only recommend the OEM torque spec. Developing and validating an alternative would be time consuming and most likely would not improve the situation.

If you look at the cylinder head bolt pattern, one will notice the outer bolts are not in line with each other (intake to exhaust). This is a design compromise due to how the coolant passages are positioned in the block. The offset bolt pattern leads to non-balanced bending forces in the head. This is not a 'best practice' or an optimized solution and certainly reduces cylinder head life.

tedder · **Joined:** Thu Sep 15, 2011 7:19 pm **Posts:** 137

Can anyone decipher the FSM?

Cylinder Head Bolt Torquing Procedure
1. Tighten all cylinder head bolts starting from the center bolts, following the cylinder head scheme and the following
sequence: 3-2-1-10-9-8-7-6-5-4-11-12-13-14-15-16-17-18.
2. Without loosening any bolts, starting from the center bolts, tighten each bolt an additional 75° in the following
sequence: 10-9-8-7-6-5-4-3-2-1.
3. Tighten the lateral cylinder head bolts an additional 50° in the following sequence: 11-12-13-14-15-16-17-18.
4. Finally tighten all bolts an additional 75° in the following sequence: 10-9-8-7-6-5-4-3-2-1-11-12-13-14-15-16-17-
18..

What does tighten really mean? How tight?
How much torque is 75 degrees?

This is insane? :?:

tedder · **Joined:** Thu Sep 15, 2011 7:19 pm **Posts:** 137

I don't know if I'm correct or not but:

1. the stock head bolts will not take 130 lb/ftl of torque with out yielding to failure. At 115 lb/ft the yield was 0.050" and you could visibly see the hour glass in the bolt.
2. to figure out the FSM I tightened each bolt per FSM just snug
3. marked 0, 75 and 150 degrees on a center representative bolt
4. tightened the center bolts to 75 deg to see what the torque was
5. tightened all the rest to that torque
6. did the same on the outer to 50 degrees also marked 125 degrees
7. tightened the rest 75 degrees using the same method
It turned out that the center torque was 100 lb/ft and the outer was 80 lb/ft.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

We recently did a torque check on the head bolts with a CRD engine at 100,000miles. The inner bolts were roughly 105 ftlb and the outer bolts were about 88 ftlb. The engine was not leaking coolant, just 16 wasted rocker arms. One rocker had come apart and the needle bearings dropped into the sump. The engine came in non-running and it will not bar over 360 degrees. We are assuming a needle bearing is jammed in the balance shaft assembly. Another engine needing to get pulled.

DOC4444 · **Posted:** Fri Apr 11, 2014 11:29 am

Do you mean the crank will not turn a full 360 degrees?

DOC

geordi · **Posted:** Fri Apr 11, 2014 12:42 pm

Tedder, I have no answer for you, other than possibly that Mopar / VM has somehow changed their bolt stock.

All of the bolts that I have worked with were BIG half-inch diameter bolts, and they never necked-down into the typical hourglass that the Volkswagen bolts do. (This is also why I hate TTY bolts)

Your situation means that I will not be suggesting stock bolts to anyone anymore. ARP studs if there is any reason to be in that far.

tedder · **Joined:** Thu Sep 15, 2011 7:19 pm **Posts:** 137

Well got her going today much thanks to everyone.

I have a trick on getting her to start after removal of the fuel rail. Just prime it by hand by turning the injection pump clockwise until you get fuel out the injector overflows.

This time took just a couple cranks and she started right up. She missed a little on #3 but cleared out.

I one thing positive out all this is I learned a lot. :BANANA:

samse2101 · **Posted:** Mon Apr 14, 2014 1:48 pm

Congratulation... :wink:

connolcj · **Posted:** Mon Apr 14, 2014 2:25 pm

DOC4444 wrote:

Do you mean the crank will not turn a full 360 degrees?

DOC

Yes, that is correct and this was my engine. The engine was hitting hard repeatedly at the same point when we tried to bar it over. My next step is to pull the engine and remove the pan to locate the lost needle bearings. We are hoping there is a needle bearing in the balance shaft assembly preventing it from baring over. Until i have get the engine pulled and the pan removed we are only speculating at this time. I hope this is the case and there is not major internal damage preventing it from baring over.

LMWatBullRun · **Posted:** Tue Apr 29, 2014 3:15 pm

tedder wrote:

I don't know if I'm correct or not but:

1. the stock head bolts will not take 130 lb/ftl of torque with out yielding to failure. At 115 lb/ft the yield was 0.050" and you could visibly see the hour glass in the bolt.
2. to figure out the FSM I tightened each bolt per FSM just snug
3. marked 0, 75 and 150 degrees on a center representative bolt
4. tightened the center bolts to 75 deg to see what the torque was
5. tightened all the rest to that torque
6. did the same on the outer to 50 degrees also marked 125 degrees
7. tightened the rest 75 degrees using the same method
It turned out that the center torque was 100 lb/ft and the outer was 80 lb/ft.

Go look at the ARP stud thread, we have the VM drawing posted for the bolts, which specifies the steel, and thus the yield point for a TTY bolt. It is far in excess of 100 fp. You will crush the head before you cause the "tty" bolts to yield.

geordi · **Posted:** Tue Apr 29, 2014 4:58 pm

Larry, do you have any thoughts then, why he may have had one of those factory bolts break or spin in the hole? I can't explain it, but I'm also not a metallurgist.

Steve_S · **Joined:** Mon Jan 28, 2013 3:32 pm **Posts:** 13

Hi,

I had the exact same thing happen, just as you described. I estimate 130ft/lb snapped it.

geordi · **Posted:** Tue Apr 29, 2014 6:29 pm

Ok, that is NOT where it is supposed to "tty" if it does at all. That looks to me like a massive change in the metallurgy that they are getting the bolts made from.

OR if there wasn't a change, then perhaps the supplier never properly set up the stock in the first place. I was unable to get one of those bolts to snap at 250 lb-ft of torque, and I was working with a nut at only the bottom 6 threads or so - so if there was a weak spot in the middle, it would have shown itself.

Something has definitely changed. I'm assuming those were new bolts?

Steve_S · **Joined:** Mon Jan 28, 2013 3:32 pm **Posts:** 13

geordi wrote:

Something has definitely changed. I'm assuming those were new bolts?

Sorry I should have given more info. I bought a 'fixer upper' 2.5 CRD so when I replaced the head I tried to re use the original bolts as this has been discussed a bit onthe forum it seemed like a good idea! The Jeep was a 2004 year with 142,000m. As with the OP the other bolts seemed to torque OK but this one just turned and turned and then 'snap'. I was experimenting with just using a torque setting rather than the 'angle' method.

When I changed the head on my 2002 2.5 CRD the bolts were different. The unthreaded portion was much longer and also thinner than the threaded portion. I bought new bolts for that vehicle and I'm pretty sure they were threaded all the way to the head. (The new bolts weren't genuine though...)

Steve

dieselguy · **Posted:** Sat May 10, 2014 10:28 pm

its something about metric thread design. I have a Kubota diesel mower and for some reason about four years ago it decided to start breaking exhaust manifold studs. I was replacing with new good quality studs and the proper nut and after about 3 hours they would start breaking off flush with the manifold. I could put the tip of my finger against the end of the stud and back it out of the hole. just today I was talking to a friend who works for what used to be dover elevators and he said the company had went to metric bolts because standard threads have more of a bevel and break off in the block and have to be drilled out and metric have a different thread design and break off different. to me it doesn't make sense. as far as torque goes,,i checked the torque on my head bolts while doing a rocker replacement at 200,000,,i torqued to 140 and none moved, I went all way to 165 and none moved. as far as for myself I will never replace factory bolts unless I break one, ive saw too many test on these and they're as tough as any other part of the engine. im all about beefing up existing week points but I just don't see any problem with these bolts, and theres been many post about this very thing.

Head Bolts Torque

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