Anyone got the lowdown on torque values for damper bolts on '65 - '67 motors vs '68 - up motors?

In the manuals for '65, '66, and '67 the torque is specified as 50 ft/lbs.

In the manuals for '68 and up the torque is specified as 160 ft/lbs minimum.

There is no discernable difference between the crank ends, dampers, or bolts.

I would ASSume that the change is not because anything about the engines changed, but because GM realized the old spec. wasn't enough.

Do I ASSume correctly?

Any juicy stories from the old days behind this one?

- Eric

 

Hi Eric
It will be interesting to see what reply this thread may get. No matter what year it is, dismantling old engines I've found removing that bolt takes about 500 ft pounds of torque

John

 

socket, 1/2" drive breaker bar and a long cheater up against the frame, give the starter a whirl and it doesn't take anything but a turn of a key Of course, if you wait to do this until AFTER you take the engine out you're back to a mile long cheater bar and 4 friends to help lol!

 

Early 65 cranks had a smaller bolt, hence the lower torque. Olds found some issues with the bolts loosening so went to 3/4 fine thread bolts (1.125" head) in mid 1965 iirc. It took time for the service manuals to catch up. All the big bolts are taken to 160 ft lb.

 

Okay.

So they changed the bolt in '65, but they didn't change the manual till '68.

Typical, no?

There must be a service bulletin saying, "Ignore the manual - just torque it to 160."

Thanks for that.
It makes sense, and I knew there would be some kind of a story.

- Eric

 

I have a custom tool for torquing that bolt down if you need to borrow it.

It ain't pretty, but it works. I welded a jack handle to a crank pulley.

 

Great idea, J, and Thanks!...
But no thanks - Now that you've given me the idea, I can weld one up myself if I need it, and save you the trouble of packing it .

- Eric