Head fastener torque

[grubby65]

I'm re-installing the head on my 1933 DeSoto and I'm trying to figure out what to torque the fasteners to.  The '33's have studs not bolts, I have the instruction manual for the car but it has no torque specs.  I found this on the internet, but I'm not sure if I agree with it.

 

Course thread 7/16" X 14 TPI  cap screws are 65 to 70 lbs as mentioned above.... 

Studs with 7/16" X 20 TPIi fine thread are 55lbs.

Cylinder head clamping force ends up the same for both styles.

 

Honestly I didn't realize thread pitch affects clamping pressure at the same torque, but the more I think about it, maybe it is correct.

Any thoughts?

[greg g]

As important as the torque  is the tightening sequence and procedure.  There is a pattern to follow, it starts with the middle center  and radiates out in a star pattern. And you do three turns around increasing the torque setting each time. 30 50 70 is what I used with head bolts.

 

The sequence goes as below till all 21 are done

        

17  11.   5. 2.  8. 14. 20

16. 10. 4.  1.   7.  13. 19

18, 12.  6  3.  9. 15.  21

 

Then retorque to final lbft`s after cooling a bit fromfull running temp heat cycle in the same sequence.

[kencombs]

23 hours ago, grubby65 said:

I'm re-installing the head on my 1933 DeSoto and I'm trying to figure out what to torque the fasteners to.  The '33's have studs not bolts, I have the instruction manual for the car but it has no torque specs.  I found this on the internet, but I'm not sure if I agree with it.

 

Course thread 7/16" X 14 TPI  cap screws are 65 to 70 lbs as mentioned above.... 

Studs with 7/16" X 20 TPIi fine thread are 55lbs.

Cylinder head clamping force ends up the same for both styles.

 

Honestly I didn't realize thread pitch affects clamping pressure at the same torque, but the more I think about it, maybe it is correct.

Any thoughts?

Think of thread pitch as an inclined ramp, which it is, just wrapped around in a circle.  The 'flatter' the ramp, the less force required to move a weight up.  Or the more force can be developed with same input torque.