Valve Adjustment - Retorque Head Studs?

[North Coast Cab]

Should they be retorqued? There seems to be a little conflicting information. I know enough to loosen and then tighten but is it a good idea?

John

[beepbeep]

Well it's a good way of checking if they are still in one piece, to begin with.

I don't see any reason not to just try to tighten them with torque wrench. If they are loose, they will tighten to right spec, if they are broken you'll be here posting usual "buhuu my studs are broken"-thread, if they are tight wrench will just click and you are happy camper.

[RoninLB]

Originally posted by North Coast Cab
I know enough to loosen and then tighten but is it a good idea?

I know what the routine technique for a re-torque is..
I don't loosen 1st

[yelcab1]

don't losen it first. Just torque.

[Doug Zielke]

What Ron said.
I've checked head stud torque 4 times since I rebuilt the 'Bombers top-end. I set the wrench for the correct figure, and simply put it to the bolt.
I've had only 1 requiring a small fraction of a turn.

[afterburn 549]

as you stated corectly loosen a little to get a correct reading on the torq. wrench. If all is well there well be no problems .If there is a weekness it will rais it's ugly (stud) head......after all its winter and more fun to fix now then on the bloom of spring

[RoninLB]

Originally posted by afterburn 549
as you stated corectly loosen a little to get a correct reading on the torq. wrench.

I understand your correct logic, but, as per my above post

I got my info from a face to face conversation with one of the biggest rep 911 engine builders in the US

[niner11]

I would be more comfortable re-torqing a motor with race ware or arp studs than one with "experienced" delivar studs. Could be a proactive approach to an expensive winter project.

[afterburn 549]

I supose he is right, but even if i am not from Mo. I like to know why?? A title dose not impress me very much but if he or they can explain thir ans. then I will take my past logic and reboot it

[RoninLB]

Originally posted by afterburn 549
IA title dose not impress me very much but if he or they can explain thir ans. then I will take my past logic and reboot it

good point..

at the time I was absorbing much info and was happy just to get his reactions to my many many non-book questions.. so I didn't ask for explanitions.. I've been thinking about the logic behind it ever since. The only thing I could dream up was that loosening the nut would disturb the head and cylinder. and I guess to overcome the striction on a low torque nut would do that.

[niner11]

who is an I.A.?

[yelcab1]

OK Here goes.

The factory calls for a slight moly lube on the surface of the washer-head nut interface to help the nut slide to the right torque. After an engine has gone a 15K (the valve adjustment interval), this lube has burned off. By loosening the nut first, and then retightening it without the lube, one is not guarranteed to arrive at the correct torque. And if one does this to all 24 nuts, then one is guarranteed to get all incorrect torque on all 24 nuts.

This checking of the torque on the headnut procedure (done during the valve adjustment) is just an opportunity to check to see if any of the headnuts have fallen off (broken or pulled studs), or loosened a great deal. By just taking your preset torque wrench to all these nuts without first loosening them, one accomplishes two things: 1) one does not disturb the nuts if they are already tight, and 2) if they are loose, one can tighten them further closer to the correct torque, which is better than to leave a loose nut ... lose.

Retorquing the nuts withouth lubing the surface of the nut-washer interface can only approximate the factory torque, but probably not totally accurate. That is all you can do during a valve adjustment.

[speeder]

Going to have to disagree here, but then I haven't checked mine since rebuild. (~6000 miles). The reason for factory recommendation to use optimoly grease on the studs, (and nothing else) , is so that nuts can be re-torqued if desired. It does not "burn off" in the period when head nut torque is supposed to be checked. Can't remember when this is to be done, but it is a short time in hours/miles after heads have been installed. Certainly not 15k miles, and re-torquing heads is not a factory recommended procedure on 911 motors, as far as I know.

Having said that, if you still want to check the torque on your heads, you would have to loosen the nuts slightly first. Unless you have an "auditing" torque wrench, (more expensive than 98% of the cars on this forum), you cannot "check" the torque by attempting to turn the nuts w/ a normal T. wrench set at recommended torque. Normal T. wrenches are

only accurate while moving!! Without beating this to death, (as it has been many times previously on this board), the amount of torque required to break a fastener loose that is torqued to 35 lbs. is more than 35 lbs. With optimoly on the threads, however, you would only have to loosen the nut very slightly in order to then re-torque it accurately. Remember, these things are only 37 Ft. lbs. (?).

As for "disturbing" the head by loosening one nut at a time, no way on earth. If your life depended on it, you could not "disturb" the head on the cylinder w/ a large hammer and 3 fasteners present. So unless you are checking the torque of these w/ the motor running under load, (never rule anything out around here), that is a non-issue. Cylinder head nuts coming loose would be an issue, OTOH. There is no reason that they should, unless something else is wrong.

[surflvr911sc]

This is really a damned if you do damned if don’t topic, meaning good arguments can be made for checking them or not. On an original 3.2 I’d say not, if they break you will know when you pull the valve covers.

Think of it as “verifying” the torque instead of re-torque. If you feel you need to check, set the wrench at 35 ft lbs and check them without backing them off. The wrench should break before you can move them so assume they are still at spec. If they are loose/broken, it should be obvious fairly quickly. Of course you cannot truly verify the torque unless you back them off and re-torque but at least you can know they aren’t falling off.

[RoninLB]

To All

sounds good to me