Al Cody

I am setting the valves and also checking on the head nuts. While checking with just a 10mm allen wrench on a couple of them I was able to get a 1/4 turn then they stiffened up. I am guessing in the 10-15 lb/ft range. Less than spec. The others were not budging.
I think I should re torque them, but not sure if I should back the tight ones off a bit then re torque them as well. Or just bring the looser ones up to spec - 24 lb/ft.
Loosening head nuts doesn't seem very common and I haven't heard of SC's pulling studs, just breaking them. I've had the car about 6 months and don't know the history.
Has anyone else had this occur? What is likely cause?
Thanks, Al

Peter Zimmermann

Al: From my experience you have a very unusual situation on your hands. SC head nuts don't even require re-torque following engine repairs. I can't guess as to why the situation exists, but if the car were mine I would torque the nuts, starting in the middle and working toward the outboard in a criss-cross pattern. I would not loosen tight ones, only bring the loose ones to spec. I would do the first pass at 18 lb/ft, then go to 21 lb/ft, then finally to 23.5 lb/ft.
Pete

Al Cody

Thanks Pete, I have experience with older aircooled motorcycles but the 911 motor is of course far more advanced. We always backed off the tight nuts and re torqued when setting valves on the pushrod twins, like Nortons.
I will go with your suggestion here. Only three of the cyclinders have under torqued nuts and then only one or two.
Thanks for your help. Cheers, Al

Al Cody

I retorqued the head nuts that needed it, all the rest were in spec. They took 1/4 turn or so. On further investigation I noted that the right had bank of cyclinders, 4,5,6 were newer than the left side. The heads were newer, shinier metal, no staining from oil on hot metal. Also the head nuts looked newer. I had a look with a mirror to see if the nuts were at the same depth relative to the nuts that were in spec...all good.
I have no history on this one, it came from a dealer that bought it in an auction...yea, I know shooting blind, not smart.
Thanks for the help.

Peter Zimmermann

Al: Yeah, somebody probably found one or more broken head studs and only did one side. Or, a tensioner failure/chain ramp failure might have led to a couple of bent valves. Has the engine been updated to Carrera tensioners?
Pete

Al Cody

It does have the carrera tensioner, one of the selling points. The heads look to be newer, so bent valves is a good possiblilty. All the workmanship looks pretty professional. Thanks for the insite.
cheers, Al