Liberty 2.8 CRD Head and Bolt Torque

DarrylMueller · **Joined:** Thu Sep 15, 2011 1:54 am **Posts:** 5

I do not like the idea behind 1/4 turn to 1/4 turn to get torque. Especial with aluminum head & leaking head gaskets.
Just wondering has any body came up with a different bolt and a standard torque. Just like to fix it once now that I see this. Not liking it.

geordi · **Posted:** Thu Feb 25, 2016 1:12 am

ARP studs. There is a big thread about them.

130 lb-ft for the center rows, 120 lb-ft for the outer rows.

Biblical commandment #11: Thou shalt not ever re-use (or use in the first place) torque-to-yield bolts, for they are of the devil and an abomination unto the Earth. Cast them aside and use quality ARP fasteners and ARP lube.

DarrylMueller · **Joined:** Thu Sep 15, 2011 1:54 am **Posts:** 5

Thank You SOOOO Much I have the them on the way, I just could not see putting junk back all the labor!

Brasher · **Joined:** Sat Mar 14, 2015 7:02 pm **Posts:** 80

There is nothing inherently wrong with angle controlled fasteners. Angle control fasteners require 3 inputs to calculate axial tension values: thread pitch, Young's Modulus of the male threads, and Young's Modulus of the Female thread. For a simple joint, all 3 of those are fixed values.

Torque control is an indirect measurement based on axial tension of the fastener, fastener diameter, and friction coefficient between the threads and the faces of the component and fastener. The last component is the kicker: For heavily torqued fastener, even a seemingly slight difference in the friction coefficient can create widely different clamping forces. Why does the friction coefficient change? Surface finish, debris, contact conditions, etc. Where torque control is favorable is when joints have variable stiffness (such as when there is a gasket between the joints.)

So how do you get the best of both worlds? Maybe you could at first, say, lightly fasten the joint using a torque control method while a gasket is rapidly compressing to decrease joint stiffness variations. The axial tension would vary less in magnitude between different friction coefficients values since the total axial tension is still low. After the joint stiffness becomes more homogeneous, we could maybe then apply an angle control method to really produce an accurate clamping force. Sure the torque values may vary widely between different fasteners, but we don't care about that as long as there is still sufficient prevailing torque to overcome vibration considerations. Our main goal is to ensure that we have even, sufficient (but not excessive) clamping force across our components.

Now where have I read a technique like this before...

Of course, none of this considers if the designed fastener tensions are actually correct, or if the technician ACTUALLY torques the fasteners correctly.

Rixram · **Posted:** Mon Feb 29, 2016 4:59 pm

ARP studs/nuts.

The notion of the stock TTY high-strength steel grinding against the threads in your aluminum block should give you pause.

papaindigo · **Posted:** Mon Feb 29, 2016 5:14 pm

Huh? the block is steel/iron; it's the head that's aluminum

Rixram · **Posted:** Tue Mar 01, 2016 9:55 am

papaindigo wrote:

Huh? the block is steel/iron; it's the head that's aluminum

This is what happens when I post on a no-coffee day.

My bad.

Liberty 2.8 CRD Head and Bolt Torque

Who is online