So Josh and I are putting his head back on after the long wait of finding a new head and having it o-ringed. Anyways, tapped the holes, blew the crap out, prepped the surface, got the head on and torqued the ARP 12mm studs. 25, 45, 90, 125. And for the bad now. 6 studs pulled out of the block at about 110-115ft/lbs. We used a moly lube on the threads and washers. Nice steady pull then crack and its downhill from there. What the heck.

So what do we do? Pull the head and get another gasket obviously. Do we drill the holes out and helicoil them? Will that hold? Or do we drill and tap all the holes for 14mm studs? Who's to say that if we repair the bad ones that more may do it at a later time during a re-torque?

When we pulled the studs out originally, they were all rusty and the holes were full or crap and oil and such. Cummins did a great job the first time on this. Not... Would the rust weaken the threads that much? I just dont get it. Where did we go wrong? Did everything by the book. Did the same thing to my truck and its holding up just fine. What gives?

 

Check the accuracy of your torque wrench?

 

Snap On digital auto-calibration. Next?

 

Not tryin to insult you, but are u sure u used the right size tap? I know you probably did, but thats about all i can think

 

With out getting an eye on your problem , my guess since you said that there was rust & ect. in the old holes , is that you may need to go the next size larger , but before do more of what your doing here [ research ] call Helicoil , some auto/truck machine shops .
If like you said tightened up with out unusual drag , just pop , I think its the rust , cut back to some clean metal .

 

Well then I guess your just screwed. Sorry I tried to help. Have a nice day. KD

 

Yeah it was the right tap. Thinking we are going to pull the block and go the helicoil route...