It's true, ARP 2000 instructions clearly state torque to 125 ft lbs with ARP ultra-lube and no retorques are necessary or recommended.
As a business owner that spends countless hours each day giving out free tech advice to diesel enthusiast callers with all levels of experience, 12v Cummins head gasket failures are extremely common, followed next by subsequent failures by guys following the ARP instructions. My first bit of advice for a frequent head gasket problem child is warm retorques. Despite the fact that ARP states retorques are not necessary, I coach the caller to try it and don't be surprised when the nuts move another 45 to 90 degrees at the same 125 ft lbs torque setting. Then for the hard causes that think the stud is simply stretching on the retorque, I coach them to check warm valve lash before and after the retorque. Magically, after doing a retorque the lash tightens up 002" to 004", despite the engine cooling off some which should loosen up the lash a bit....
Anyway, say what you want, I went through about 5 head gaskets in one race season before I finally went back to the cheaper ARP's and torqued them dangerously high. I went as far as pulling the engine, getting it decked flat, raising oring protrusion, installing the stiffer Hamilton Head, trying numerous torque and retorque sequences on the extreme studs, factory head bolts, and one time with the ARP 2000's at 125 ft lbs before I received a tip about these magical ARP 2000's holding up to 160 ft lbs of torque on a common rail. So I tried it on the Junker, took them to 150 ft lbs cold, retorqued at 150 ft lbs on a warm engine, scared to death they were going to break when I got 90* or better on a couple. Took it easy for another heat cycle and hit them again at 150 ft lbs and this time one 3 or 4 broke free. We then hit it hard on the dyno and the head gasket held!!! After a week or so, I decided it was holding pretty well so we bumped the timing higher to see if I could make it blow, because it's never held even one pull at 30* timing.
Fast forward a year or so and it's on the same head gasket, it's been warm reqtorqued 4 or 5 times now to check and they are rock solid tight, timing is now at 34* total advance at full rack travel. And it's going rounds at the drag strip, on the dyno, burnouts in the parking lot, joy rides with customers, etc. In hindsight, if I could take back all the blown head gaskets, wasted labor time, wasted coolant, wasted oil, lost race opportunities, the $1,200 ARP 625's would have been a better purchase than the $450 ARP 2000's. But knowing what I know now, ARP 2000's are a viable option for 1000 HP 12v with simple orings if torqued well beyond the manufacturer's instructions.
One thing I have noticed though, when we use real ARP 625's and torque them to ARP spec of 150 ft lbs, they move much less, maybe 45* max on the first warm retorque. If we bump them up into the mid 160 ft lbs range, they almost don't need a retorque as most don't budge when checked. So for the average high HP non-DIY customer that has to pay a shop to do retorques, there's a much higher chance for success using 625's with no retorques.
