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Discussion Starter #1
So 10 minutes ago, I am torquing the head on my 4BT that I just finished putting back together. I'm on the final stage of torquing with the +90 degrees section. On the final bolt, it makes a loud snapping noise. So I take just that bolt out to try and save the gasket and use the inspection camera on the threads in the head. It looks like one individual thread might have stripped but I cant tell for sure as it might just be some thread sealer. Anyone have this happen or know the cause/fix?
 

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Not too often we hear of a thread stripping in the block. Bolts are known to sometimes break. Were these new bolts or used ones. There should be no thread sealer on head bolts. You use oil on those to get a proper torque. Did you run a tap in the bolt holes before installing the bolts. Might use a bottoming tap. Then take a look if possible to see if there is damage to the block or just the bolt that gave way. Head gasket should be OK as long as it's just 1 bolt. Although many don't do it, this is a good reason to install head studs. A little extra money but they can be used over and over.
 

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I had a bolt in my 6bt pop from somebody previous to me torquing it down without it being lined up on the water jackets. So the top 1/2" of the threads were bad. I ordered a longer bolt of the same grade and thread from Fastenel, ran a tap all the way to the bottom of the hole to make sure there were good threads down there still (there were, more than the original bolt went into) and ran the longer bolt into the good threads deeper in the block.
 
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If all but the top 2 or 3 threads are intact I would feel confident using a stud in one hole,but I would only torque it to the specified torque and not the added 90* sa you get more clamping force with a stud than you do with a bolt at the same torque.............$.02
 

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If the bolt was fully inserted it will not pull just the first couple of threads unless the bolt was the wrong length.
As asked above did you tap the thread holes before re-assembling and oil the threads? Lack of oil on the threads and UNDER the bolt head can cause a snapping noise as torque is applied.
What do the bolt threads look like?
Cheers Steve
 
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Discussion Starter #7
I did thread chase every head bolt hole and use 10w 40 for torquing. What I though was thread sealer was just one of the stripped threads being heavily illuminated by the camera. After further inspection with an inspection camera, the 2 threads that stripped were in the middle of the hole. Very weird but may have been cause by corrosion. All other threads are intact and the head bolt can be tightened with a ratchet all the way down before the torque sequence.
 

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If all but the top 2 or 3 threads are intact I would feel confident using a stud in one hole,but I would only torque it to the specified torque and not the added 90* sa you get more clamping force with a stud than you do with a bolt at the same torque.............$.02
I don't understand how it is that clamping pressure would Change from stud to bolt, with the same amount of torque on the wrench?
The last time I installed the head I bought new bolts but when they came in the 7&1/2" ers that bolt through the rockers were not there, so I called, they said these were not available so I had to use my old ones ! When installing I put oil on all threads & moly on all bolt flanges but at about 65/70 ft/lbs torque, When starting final sequence, several were popping, I took them out added more oil, no good, out again wiped, added the assembly lube to the thread, successfull, no more popping!
Also what is this torque then add 90* . To me this would grossly over torque

Should I look for those 7&1/2"ers?
Does anyone retorque after the engine has gotten hot?
 

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If the bolt was fully inserted it will not pull just the first couple of threads unless the bolt was the wrong length.
As asked above did you tap the thread holes before re-assembling and oil the threads? Lack of oil on the threads and UNDER the bolt head can cause a snapping noise as torque is applied.
What do the bolt threads look like?
Cheers Steve
This. Your bolt was too short for some reason.

You want about 1.5x the diameter in the threads. If you have less then you want to check everything.
 

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Papa, bolts and studs do not clamp the same way. On a bolt, when you twist the head you are also twisting the entire length of the bolt and stretching it. With a stud, it is installed in the block and only the nut is twisted to obtain the torque setting. Very little stretching occurs to the stud. Due to this the studs can be uses over and over where the bolts quite often must be replaced due to the stretching.
 

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Dougal,,, yes, I always try to have more threads than the diameter of the bolt, in aluminum I like double, in fact I have replaced & used non-stock on bellhouseings to accomplish such!

Char1355,,,,Thanks for the explanation! What about torque & 90*? & Replaceing those 4 long ones? Does anyone re- torque after the engine has gotten hot?
 

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With OEM head bolts, use the OEM torquing procedure. Replace used head bolts if they've stretched more than allowed by cummins bolt stretch gauge.

With ARP head studs or otherwise, use the procedure provided with those fasteners.

Retorque after a heat cycle or two is a good thing, but not necessary at mild power levels.
 

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GLTHFJ60 . Thanks,I understand the FJ60,( I have a FJ40-1972), what's the GLTH?
I don't have a Cummings stretch gauge , AND
Since this tractor is a 1990 and found it had been rebuild before I bought it , I thought it good to replace head bolts, BUT the 4long ones did not come with the set, so now I have to try & find them
 

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