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What is the proper torquing technique for head studs? - Top
- While some manuals specify a rather detailed (and difficult to remember) sequence, we have a rather simple system in our own shops which seems to work very well. We simply start with the center stud and work outward in circular fashion until all studs are torqued.
We do put a great deal of importance on starting at a lower value (we use 25 foot-pounds) for the first trip around the head. We then increase the torque value by 5 foot-pounds on subsequent circular patterns until reaching the factory recommended torque value of 35 foot-pounds.
IMPORTANT NOTE: In discussing torque values with Universal technical service folks many years ago, we were informed that Universal had successfully tested engines with torque values as low as 30 foot-pounds. For this reason, they suggested that if you have any question as to the integrity of the lower threads in any of your studs, you're probably safer to stop as low as 30 foot-pounds. The concept here seems to be that it is better to have a "solid" 30 foot-pounds on a stud than a "soft" 35.
There is some debate among the experts with whom we network regarding whether or not the torque values were designed with the upper threads of the studs being oiled or dry, the concern being that, if the torque value was designed for dry threads, then the lower friction resulting from oiling them will result in a slightly larger "pull" being applied to the studs at any given torque value.
Our own sense of the oil/dry issue is that you're probably a bit better off using oil on the threads (the type is not important), simply because it is so difficult in most cases to insure that the threads are "laboratory" perfect. Again, with respect to the above note, if you're at all concerned over the integrity of the lower threads of a particular stud, stop at a torque value between 30 and 35. - Updated:
November 24, 2003
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