Does the torque value need to change when you use a thread lubricant? For example, the manual gives 16.5 ft. lbs. for the exhaust header bolt, but after using some Never-Seize, I was afraid to tighten to the recommended setting because it seemed that I was about to strip the threads. The torque wrench is accurate. Thanks,
I was always taught that never-seize and thread lock does not change the value of a tourqe setting. But I'm not where you are so don't cry to me if you snap that header bolt off!
most specified torque values are given for a dry friction condition between parts. proper tightening torque is proportional to the coefficient of friction between the surfaces, head/nut and threads. last i recall, in general tightening torque should be lowered by about 10-25% when lubricants are used, depending on the lube and materials involved. also, the coefficient of friction is increased with lock washers and lock nuts. most torque wrenches require frequent recalibration to remain truely accurate. hopefully that'll point you in the right direction. Cedric Williams
Still doing some research but it looks like I was wrong and Op 40 is right. Loc-tites site is full of equations that I don't have the higher brain functions right now to decipher... But this came off a commercial bolt site: BOLT TORQUE FACTORS LUBRICANT OR PLATING TORQUE CHANGES Oil Reduce torque 15% to 25% Dry Film (Teflon or moly based) Reduce torque 50% Dry Wax (Cetyl alcohol) Reduce torque 50% Chrome plating No change Cadmium plating Reduce torque 25% Zinc plating Reduce torque 15%
TJR, just another little bit of info. You better pull that bolt back out and check it. Get 2 together and look at them both. If right under the head(the one that felt like it was gonna strip) looks smaller than the other one. You better replace it, the head is about to snap off. IT started twisting and that is wht it felt like you were stripping the bolt. Been there done that on smaller bolts. So everytime I remove a bolt now, I always look at the threads right under the head of the bolt.
Check www.headgasket.com/index.html , Click on Physics, scroll down to torquing and bolt loading. It might not help with your question but it makes interesting reading.
