Camshaft Lockbolt

[runner74]

Hello

I have a 1974 Chassis service manual that clearly tells me that the 440-440 Camshaft lockbolt torque spec. is 50 foot pounds (Page 9-89)

When checking internet sites most say 35 foot pounds some say 40? What gives. What is correct? I have tightened it to 50 and now am worried I should back it out or replace it.
When searching just for 7/16-14 grade 8 it does say 50.

What say you ?

 

[69Bee]

Chevy head bolts and main bolts (both 7/16"x14) get tightened to 70 ft/LB, so I would not be afraid to leave it, especially when the manual says 50 ft/LB.

 

[runner74]

Thanks Bee

I am thinking the same now too. Page 9-61 says 50 also, unless it was a miss-print.

 

[HT413]

You'd feel it if you over torqued it. Instead of getting harder and harder to turn, it kinda has a sick, stretching feeling and gets maybe a little easier to turn rather than harder.

 

[snakeoil24]

HT413 is right on! Bolt stretch is a big failure issue if it exceeds specs. Did you replace bolt anyway when let's say you did, when the cam shaft was replaced??

 

[runner74]

HT

I used the original bolt. Like bee says should be no worries. The head bolts are the same size and get tightened to 70

 

[runner74]

Here is a better one of 9-61. It's hard to bend the book for the scanner. Don't want to ruin the book.

 

[Yatzee]

Hello

I have a 1974 Chassis service manual that clearly tells me that the 440-440 Camshaft lockbolt torque spec. is 50 foot pounds (Page 9-89)

When checking internet sites most say 35 foot pounds some say 40? What gives. What is correct? I have tightened it to 50 and now am worried I should back it out or replace it.
When searching just for 7/16-14 grade 8 it does say 50.

What say you ?

The grade of bolt determines maximum torque for that thread pitch. Anything above can cause failure. If your bolt were a grade 10 the max would be higher but there are other considerations to take into account, namely the threads in the camshaft. Tapping and threading are done using "percentages of thread" which could be as tight as 95% or as little as 80%. Cut deeper and you have weaker threads that stretch, cut shallow and you may pull the threads completely. Not knowing if your bolt threads and cam threads match, I'd go 40 with blue locktite, afterall, your not holding up 200 lbs with one bolt.