5.0L carnage

[AtomicLabMonkey]

This is random, but thought it was interesting... one of the guys that works here had his motor let go during the OTC. His current failure theory is that since he used stronger aftermarket ARP studs/nuts to clamp down the crank bearings, the higher required torque/preload for those fasteners overstressed the block casting in the thin webbing areas underneath each hole. Racing is quite expensive already, let alone when things like this happen... :shock:

[img:18d141bf34=800]http://home.comcast.net/~jhidley/DSC01805.JPG[/img:18d141bf34]

http://home.comcast.net/~jhidley/index.html

[MikeSTI]

ochie

[ArthurS]

That looks painful....

[sperry]

That must have included a fantastic THUD! when it happened.

[Kevin M]

A little JB Weld will fix that right up.

[AtomicLabMonkey]

Originally Posted by sperry

That must have included a fantastic THUD! when it happened.

From what I heard it didn't; the motor just lost oil pressure and when they pulled it into the pits & opened the hood, there was oil & coolant all over the engine bay. Upon closer inspection under the car the external cracks in the block were discovered...

[sperry]

Originally Posted by BAN SUVS

A little JB Weld will fix that right up.

[sperry]

Originally Posted by AtomicLabMonkey

From what I heard it didn't; the motor just lost oil pressure and when they pulled it into the pits & opened the hood, there was oil & coolant all over the engine bay. Upon closer inspection under the car the external cracks in the block were discovered...

So no catastrophic engine failure? If I ever have to replace the block, I want the old one to go out in a blase of glory... and by glory I mean white smoke, spraying oil, and lots of noise.

[Dean]

Originally Posted by AtomicLabMonkey

higher required torque/preload for those fasteners?

Huh? Fasteners do not normally define the torque, the materials you are fastening, or the tolerances in the parts determine the torque. Otherwise you have failures like this, or deform parts in a manner which might contribute to failure.

I agree with the cause assesment based on the damage, but the fault lies in the higher torque placed on the fasteners, not the block materials or design IMHO.

Just beacuse you use a higher grade bolt/fastner in an application does not mean you increase the torque on the fastener. If anything, i would think you might decrease the torque as the fastner would have less stretch.

I need to go back to my college materials class...

[sperry]

Originally Posted by Dean

Huh? Fasteners do not normally define the torque, the materials you are fastening, or the tolerances in the parts determine the torque. Otherwise you have failures like this, or deform parts in a manner which might contribute to failure.

I agree with the cause assesment based on the damage, but the fault lies in the higher torque placed on the fasteners, not the block materials or design IMHO.

Just beacuse you use a higher grade bolt/fastner in an application does not mean you increase the torque on the fastener. If anything, i would think you might decrease the torque as the fastner would have less stretch.

I need to go back to my college materials class...

I thought the fastener requires a certain amount of torque because lower torque would allow the threads to back out.

For example, a high-grade nut/bolt would require more torque than a lower grade because otherwise the threads would not stretch enough and therefore there wouldn't be enough friction to keep the nut on.

[Dean]

Originally Posted by sperry

I thought the fastener requires a certain amount of torque because lower torque would allow the threads to back out.

For example, a high-grade nut/bolt would require more torque than a lower grade because otherwise the threads would not stretch enough and therefore there wouldn't be enough friction to keep the nut on.

I only think a change in thread pitch would require change in torque. The torque is generated by the friciton between mating surcafaces regardless of the stretch of the materials, so the same amount of friction would keep something with the same thread just as tight.

Now if the higher grade fastener had a higher expansion rate under operating temperatures, then it might need more torque.

[AtomicLabMonkey]

Originally Posted by Dean

Huh? Fasteners do not normally define the torque, the materials you are fastening, or the tolerances in the parts determine the torque. Otherwise you have failures like this, or deform parts in a manner which might contribute to failure.

Let me restate that; I believe (this is secondhand knowledge, mind you) that the torque values used on the fasteners were recommended by ARP based on the particular stud and the assembly lube used. My guess is that ARP just recommended a stud preload based on its proof strength without doing any analysis of the application (the Ford 302 engine block) itself. It appears that this was a bad idea.

[AtomicLabMonkey]

Originally Posted by sperry

I thought the fastener requires a certain amount of torque because lower torque would allow the threads to back out.

For example, a high-grade nut/bolt would require more torque than a lower grade because otherwise the threads would not stretch enough and therefore there wouldn't be enough friction to keep the nut on.

Most required torques on fasteners are not specified to keep them from just loosening, they're specified to impart a clamping force on the joint. If you torque something down enough to impart any serious clamping force, the fastener is not going to back out.