Bob D..

I have searched this but couldn't find an answer. This is for a 3.2.
Factory manual says 11 ft-lb then 90 degrees, with no mention of re-torquing
One book and several posts say two stages, final tightening to 23.5, with re-torquing after a bit of running.
I followed the factory method - the nuts are considerably tighter than 23.5.
Also, there is no way to re-torque later with the tighten then 90 degree method. To the best of my knowledge, when bolts are tightened by a stretch method (which essentially the factory method accomplishes) there is no need for later re-torquing. Properly installed rod bolts would be an example.

So, what is the right thing to do?

Peter Zimmermann

Bob: Your instincts are good - no re-torque is needed on that engine.
Pete

Bob D..

Wasn't entirely instinct - mech eng + some experience designing bolted connections helped.
It is interesting that I couldn't find any references on this - and it is potentially confusing, possibly with very nasty results.

Peter Zimmermann

Bob: I fully understand, and you got me thinking about this. I really can't recall any 911 fasteners that require a re-torque except, incredibly, cylinder head nuts! But that only applies to 2.7 liter and earlier engines with magnesium crankcases. Of all the SCs that we put new head studs on, or had the engine apart for other reasons, we never found a head nut that had loosened, and the torque for all of those engines, until the change was made to the instruction that you used, is 23.5 lb/ft. The mag case engines, on the other hand, wiggled around alot until everything found a happy place; we always found a few head nuts on those engines that had loosened. But, at the first major service following the repair a loose nut was extremely rare, but we torqued every nut on every engine anyway. Lug nuts, shock tower nuts, suspension/axle hardware, transmission fasteners, intake manifolds, etc., never loosened over time. Porsche went to one-time-only use hardware, for many suspension/steering fasteners, some time ago; if those pieces are re-used they do loosen. Also, conrod bolts/nuts have always been use once only, so there is not an issue with that either. But it's a very interesting topic.
Pete

Bob D..

One of the interesteing aspects is that with the 11ft-lb then 90 degrees instruction, there is no way to re-torque (actually re-tighten is possibly a better term). The only way would be to loosening them off, set to the 11 ft-lb , then turn 90 degree, which gains nothing.
I guess one could test to see how tight they are initially, but that involves possibly over-tightening as you find the torque setting, and in any case it is unlikely to be uniform.
I think the turn of the nut method is a good one and in my engine I am going to leave it alone.