Bolt torque discussion

MopaR&D said
Most fasteners on engines are spec'd to a torque well below the plastic deformation range (where the metal starts to "stretch" farther than it can spring back). Very high stress areas such as heads and connecting rods need all the clamping load they can get so that's why you see TTY bolts more often in those apps. It should be verified with ARP but I don't think the vast majority of their fasteners are meant to be loaded to the point of yielding; their specialty is making extremely strong fasteners that don't need to be stretched to get the most clamping force; since the metal itself is stronger the bolt/nut can be torqued farther before the metal starts to stretch.

If I can add to what has been said above...... Yes on the ARP approach... they are not meant to be used past the yield point.... the tension/stress would probably tear the mating threads out first! They are used for more clamping force; this helps hold head gaskets in place better, keeps rod ends more stable in shape under load, and reduces the movement and distortion of the main caps under load.

TTY bolts are not actually for maximum clamping force, but for more consistent clamping force.

Torquing non-TTY standard bolts to a set torque level gives a pretty wide range of resulting clamping force. OK for old factory stuff.
Lubes on threads helps to make a more accurate translation between torque and clamping force, which is why ARP supplies it.
TTY makes sure a specific section of the bolt enters the deformation region when tightened with a certain procedure, and the materials and design of that 'yield region' of the bolt are selected to make it do that without getting too close to failure. The tightening method puts the bolt more consistently around a given clamping force point than the simpler torquing procedure. Think of it like a pressure relief valve on an oil pump.... you can have a lot of variations in speed on the pump but the pressure stays pretty constant. Same thing for a TTY bolt versus installation variables.