'93 4.0 Flywheel to Crankshaft Torque - Stripped

[fursphere]

Need some help please.

I was prepping my freshly rebuilt 4.0 to to reinstall in the XJ today. Installing the flyhweel onto the crankshaft.

Looked up torque specs - Haynes manual I have and everything I could find online said 105 ft/lbs. Sounded right to me, so I started started slowing tightening things up.

One of the bolts totally stripped (threads in the crank stripped). I chased the threads with a tap and tried again - didn't even get to 75 ft /lbs.

so.. at this point I've got an extremely expensive paperweight.

Can it be fixed?
And is that torque spec correct? I started digging around and found the flexplate (automatic) torque specs were like 55 ft/lbs? Is it really 55?

I found a PDF of the '93 FSM - and its a complicated mess to try and understand what its saying.

Any help is appreciated, but that this point i'm about to lose my mind. :bawl:

 

[ljobbins]

I dont see any reason why an engine machine shop cant fill in the hole, tap and rebalance if neccessary.

 

[RCP Phx]

That's the correct torque, so maybe look into Heli-coils! There must have been something wrong with the existing threads?
My ARP flex plate bolts torque to 100 ft/lbs.
A rebuilt exchange crankshaft would be the simplest.

 

[fursphere]

Can helicoils take 105 ft/lbs of torque?

I had to helicoil the heads on my silverado when the machine shop screwed up the intake manifold bolts - and they're only like 18 ft/lbs, and they BARELY held after that.

I can't imaging putting 100+ on a heli coil.

 

[Jeep Driver]

you might find this interesting http://www.hotrod.com/articles/how-to-repair-crankshaft-threads/


In your case, I'd replace the crank.

 

[fursphere]

Replacing the crank, directly after a full rebuild, it a damn expensive way to fix the problem. But its on the table.

I'm going to take it back to my machinist and see if he can fix it. And probably have him install the flywheel too - so if it strips out again (or another one of the damn bolts strips) its already there.

Thoughts of stripping everything good of my XJ and transferring the parts to my LJ are ringing loud in my head though...

 

[RCP Phx]

You can get a crank w/ bearings for 200$ and all you need to do is pull the pan!

 

[RCP Phx]

One last minute thought, make sure the bolt threads are long enough! Someone may have used flex plate bolts.

 

[fursphere]

Pretty sure they're the right bolts. I'm going to order a new set anyway.

Engine is going back to the shop tomorrow morning - machinist thinks he can fix it. I'll install the flywheel there in case it strips again.