Sheared flywheel bolt

[philminotti]

I have a RAM aluminum flywheel and used ARP Pro flywheel bolts.  When I initially assembled the engine, I used low strength Loctite (purple) in case I need to dissasemble it after testing.  The bolts where all torqued to 100 ft-lbs and no lube was used under the bolt heads.  Last night, I figured I'd beef up the loctite to blue for final assembly.  As I torqued the last bolt to 100, the head sheared off.  This was only the second time these bolts were torqued.  Impact wrench was never used.  Is this a case of a defective bolt, or should I have used lube under the bolt head to prevent galling of the bolt head on the aluminum flywheel?  There doesn't appear to be any evidence of galling.

phil

P.S.  there is a photo, but it doesn't appear unless you log in.  Not sure why.

[ScotiaFE]

It appears to be a sideloading fracture, meaning the head was only seating at a small single point.
This will put a side load on the head and body and causing a crack to form.
You can tell by the raised point on the edge of the bolt body which is a sign of pulling apart rather then shearing.
There also appears to be some fatigue cracking on the opposite side.
The bolt may have been too hard to take the sideload and fractured.
I'd have a good look with a glass at the bolt hole also.
It may have some cracking.

I would send it back to ARP with your explanation and see what they have to say.
They will say WHY DID YOU NOT USE THIER LUBE.
It's always the guy with the wrench that made the bolt fail. lol

[jayb]

Why 100 ft-lbs or torque, Phil?  That may have contributed to the problem; I usually torque flywheel bolts to 75.  But I have also seen the ARP flywheel bolts fail just like the one in your picture.  Howie is probably right about the cause...

[philminotti]

Thanks for the thoughts, guys.  I thought I'd read that the spec for the flywheel bolts was 100...maybe 75 would be better lol.  Perhaps I'll have the bolt holes lightly spot-faced as well.  It was so much fun getting the flywheel off over the deformed bolt shank...

[Qikbbstang]

with no difference indicated for 390-427. Interesting concerning the use of a locking thread sealent

[Ford428CJ]

Not really BB. Loctite works well for that. I like to use the gel. OEM now a days use the gel type Loctite. Good stuff! BUT use very little. It doesnt take much. JMHO

http://www.youtube.com/watch?v=bzP7HYG4qp4&list=PLBLUhpqCZkZIIwuKD5aF28IJ83n_e9hV-

[Ford428CJ]

Here is the stuff I use most. Works great!

http://www.permatex.com/products/product-categories/thread-compounds/threadlocker-gels

[Qikbbstang]

flywheel bolts the 50ft lbs is with oil on threads and the 70ft lbs is dry. He warned that particularly on diesels with high bolt torques the cranks flange face should be checked prior to assembly for warping/distortion at the threads. He also mentioned some motors are bad about self loosening up crank/flywheel bolts due to harmonics.

[zukinut]

I prefer the gels as well. Little more expensive but works great. On my Harleys the gel seems to work better than the more liquidy type.

I also agree with scotia. Were their any indications on either side of the flywheel that would indicate it not sitting flush?

Will