The last time I spoke to an engineer from ARP ( I was a WD for them at one time) we had a long talk about the yield strength and torque specs. We also spoke about bolt and stud stretch. The conversation included the reasons for why the specs are what they are and why. The bolt or stud must be stretched to provide clamping force. If the bolt or stud is stretched too much it losses its ability to clamp effectively as the elasticity is reduced. Remember that once an engine is warmed up the heads and block grow a little and stretch the fasteners more, that is why you sometimes find that you need to re-torque. Once the fasteners have stretched after being tightened and loosened 3 times they tend to stay were they were. Most people don't follow ARP's recommendations and don't tighten and loosen the fastener 3 times to spec begin with. I have had great luck by following the advice ARP gives and have had no head sealing problems in any of the ARP equipped engines we build. To add one thing about over-tightening fasteners. Did you ever think about the bore distortion that it causes, the deck distortion, the cylinder head distortion? It lends that deck and head distortion from over-tightening can cause more problems that over-tightening my solve. Also unless the cylinders were honed with the deck plate that that level with the exact same set of bolts they sure are not round when you do this.
Just my .02, your results may vary.
Just my .02, your results may vary.
