What is the Torque for 911 Valve covers

[kyriakos59]

Please someone advise on the torque needed for tightening the valve covers, upper and lower for a 1974 911 Carrera CIS. 8 Nm from Wayne's rebuilding book seems very low. My tool also starts from 12 Nm.

I have applied 30 Nm. Is it too much ? What are the consequenses for a higher or lower torque than the proper one needed ?

[tuned6]

Over torquing a bolt will cause several different problems. You will weaken the fasteners and make them more prone to coming loose that if you were to under torque. Over torquing may also cause the studs to pull from the parent metal or to stretch and shear or crack what it is fastening, like your valve covers. Proper torque is important.
For these valve covers the stud and nuts are 8mm x 1.25 pitch I believe. The rated torque for this size threads is 14ft. lbs.
18ft. lbs is the given measurement for certain applications for this size and will be listed in the service manual.
For the valve covers you should be using nylon lock nuts and I believe the torque is going to be 14ft. lbs. Depending on your experience this may or may not seem like too much torque. It is why a torque wrench is such a valuable tool. The nylon nuts will prevent the nuts from ever falling off if you lose your torque as the gaskets settle. I would go with 14ft. lbs. and retorque the nuts after a few heat cycles as the gaskets settle.
The most common problem I see is under torqued spark plugs. All different size plugs have a different torque. Small peanut plugs go to 18lbs. and 14mm plugs to 25 ft. lbs.
With improper torque on spark plugs you will have your plugs begin to walk out of the hole and take the threads with them. Next time you have your plugs out look to see that the crush gasket is flat and it will tell you how you are doing 'by feel'.

Good luck,
Christopher

[safe]

Originally Posted by kyriakos59

I have applied 30 Nm. Is it too much ? What are the consequenses for a higher or lower torque than the proper one needed ?

Way to much!

I just snugg them up and if they leak tighten them a bit more. The upper valve covers almost never leak.

[tom1394racing]

Over torquing can warp the covers and then they will never seal.

[777joee]

As per Wayne's book on page 200. Valve cover nuts, M8 8Nm(6ft-lbs.) Tighten further if leakage occurs.

[Eagledriver]

Did you notice how easy they were to remove? These are very low torque to keep from warping the covers.

-Andy

[RichHawk]

I checked the Bently manual for my 87. it also says 8Nm (71 in lbs).
which is almost 6 ft lbs.

It sounds like this is a good excuse to go out and buy a in lb 3/8 inch drive torque wrench.. I got mine.

[Aurel]

I cut a chinese made wrench in half for that purpose, and I do it by feel. It gives more clearance and prevents applying too much torque on the bolts. I also do it by eye, because I have silicon gaskets, and if there is too much pressure, they will expand out of the seal. No leaks with that method.