Vibration damper bolt torque spec, 100 or 135 foot pounds

[idrivemopar]

Interesting dilemma for the torque specification for my vibration damper bolt! My 73 service manual states 135 foot pounds in the install instructions but the specification sheet in the manual for the 340 states 100 foot pounds. I also looked in my old Chilton's, and it says 135 except for 71 where it is 100.

So, does anyone know which is correct and is it because the difference between forged and cast crank?

 

[Cranky]

Even if you use 100 ft lbs, it won't come loose for sure if you put a dab of Loc-tite on the threads. It has an interference fit and the main reason for the high torque is it sees plenty of vibration from the crank.

 

[dvw]

factory spec is 135, did mine this morning.
Doug

 

[idrivemopar]

factory spec is 135, did mine this morning.
Doug

What motor?

Also, did you use thread locker, when I took mine off it didn't take as much effort as I thought and there was no thread locker used by my builder.

 

[dvw]

What motor?

Also, did you use thread locker, when I took mine off it didn't take as much effort as I thought and there was no thread locker used by my builder.

This one, no thread locker, only oil on the threads.

 

[idrivemopar]

Big block is 135, I have seen that in multiple places, but for small block, I need to know if its 100 or 135 as per my original question.

 

[bm02tj]

My 73 manual is 100 for small block and 135 for big block and both are 3/4 16 bolts

 

[dvw]

Same bolt

 

[idrivemopar]

I get that, but is the torque different for cast versus forged crank?

 

[Hemirunner]

The bolt material would make more of a difference than cast vs forged steel. Standard torque table on a grade 2 soft bolt in. a 3/4-16 is 138ft/lbs. Use a grade 8 bolt and it jumps to 315ft/lbs. 130 is pretty safe territory....

 

[idrivemopar]

Thanks, no idea what grade the bolt is, its the original factory bolt, and it just has 37 stamped on it.