ARP STUD INSTALL BLOCK THREAD FAILURE

[justinray]

Fwiw, when tightening something like this, you should hold back up on the stud (with the allen wrench that fits the hole on top, maybe) to avoid the stud turning in the block instead of the nut turning on the stud. May have been the problem.

 

[IDIoit]

Fwiw, when tightening something like this, you should hold back up on the stud (with the allen wrench that fits the hole on top, maybe) to avoid the stud turning in the block instead of the nut turning on the stud. May have been the problem.

kinda hard to do with a torque wrench?

 

[laserjock]

Did you put lube on the bottom threads? My guess is its a combination of weak threads and the stud turning against the bottom of the hole pulling the threads out.

 

[FORDF250HDXLT]

these places such as ARP have very,very,very highly skilled engineers and top of the line equipment for measuring and testing such things to come up with their torque values.when you think you can do something at home or in your shop such as torquing a ARP stud down past what they recommend just because it doesn't go "snap" right off,then your fooling yourself that you know better than those highly payed,best in their field collage grad engineers with their measurement equipment that we probably can't even spell let alone use lol! follow their torque values.don't go beyond and don't let someones rusted out threaded bolt holes scare ya guys from torquing to what they recommend either.this is simply a case of an old engine block that's seen better days.rusted threads will eventually fail.......stuff happens.but hey,look on the bright side,better in the shop than while boosting 10-15 lbs 50-100 miles from home.

 

[PwrSmoke]

these places such as ARP have very,very,very highly skilled engineers and top of the line equipment for measuring and testing such things to come up with their torque values.when you think you can do something at home or in your shop such as torquing a ARP stud down past what they recommend just because it doesn't go "snap" right off,then your fooling yourself that you know better than those highly payed,best in their field collage grad engineers with their measurement equipment that we probably can't even spell let alone use lol! follow their torque values.don't go beyond and don't let someones rusted out threaded bolt holes scare ya guys from torquing to what they recommend either.this is simply a case of an old engine block that's seen better days.rusted threads will eventually fail.......stuff happens.but hey,look on the bright side,better in the shop than while boosting 10-15 lbs 50-100 miles from home.

You could be, are very likely to be, correct in what you say ... but even pros make errors and sometimes it pays to question when there are anomalies. There are a few question in this that need answers in order to reach a conclusion about what happened. It's not likely we, the forum we, will ever really know what happened but the discussion of the problem can have some benefits. Maybe it will make people look more closely at the instructions. Maybe it will help people to take more time on the details. Maybe ARP will go back and look at this and say, "Whoa! We need to rethink this." Or maybe it will just degenerate into a typical internet forum urination contest. Hope not!

 

[IDIoit]

the biggest thing i can contribute is to NEVER chase threads with a CUTTING tap.
most people think "ahhhh itll be alright"
but threads arnt something you want to be recutting,
only when repairing.
my .02

 

[Black dawg]

You could be, are very likely to be, correct in what you say ... but even pros make errors and sometimes it pays to question when there are anomalies.

Hopefully they offer some insight. Maybe just crappy threads in the block, but it would not be cool if this happened to several more 7.3s before it got any attention.

It should be pretty obvious by looking at the end of the studs and the bottom of the holes, if the studs were bottomed out and turned hard enough to push the threads out.

 

[G. Mann]

Perhaps the lesson we can all take away from this piece of bad luck by one of our members is to give the block threads a very good inspection while we are cleaning up everything before re-assembly.

The threads are relatively fragile compared to the bolts, considering the load they are under. Add to that load the thousands of times they are heated then cooled in their lifetime. They are a "working part" just as important as rod bearings or rocker arms. Guess we need to start treating threads as a part to be inspected at each access.

 

[kcwright1979]

Ok so I got to the bottom of what caused the fialures. The ford OEM head bolts have 1.500 in of threads to grab the block with. The arp studs have 1.250 in worth of threads. the block holes are 2.500 deep with a 1.000 countersink and 1.500 in threads. With the lack of that .250 thread grab and weak threads resulted in the failure. The guys wondering about helicoils being strong enough they have a failure point of 200,000 psi which is the same as the head studs itself and with a max torque value of 150 ft/lbs. if it doesnt work ill be looking for a IDIT short block. so far I have step drilled and tapped four of them with no problem. I tested some helicoils they were the .750 length on a peice of cast iron I had laying around and used a grade 8 bolt and torqued them to 160 trying to get it to strip out and it wouldnt happen. did this process bout 4 times. I ordered 1.250 helicoils so the stud will have full thread engagement.

 

[The Warden]

The ford OEM head bolts have 1.500 in of threads to grab the block with. The arp studs have 1.250 in worth of threads. the block holes are 2.500 deep with a 1.000 countersink and 1.500 in threads. With the lack of that .250 thread grab and weak threads resulted in the failure...I ordered 1.250 helicoils so the stud will have full thread engagement.

You're right that that the bolts have more thread area than the studs do. However...I did some experimenting when I got my ARP studs before installing them on my engine. I'm running late for work, so I'll just link you to my write-up where I did the comparison. This is on a 6.9l, so YMMV...but, IMHO it's worth taking a look at:

http://www.dieselwarden.net/ford/project18.html

 

[PwrSmoke]

When I did my engine a few years back, the Warden had done his investigation (useful info). I saw it, thought it interesting and more or less looked at my engine the same way. I made the same observations as to how deeply the threads went into the block and confirmed his numbers. Barring the possibility that you were given the incorrect studs, something that is easy checked, I think you are barking up the wrong tree here.