Finally stopped torquing dry exhaust bolts, wish I learned this sooner

Been turning wrenches at a fleet shop outside Tulsa for about 4 years now. Last month I had a 6.7 Cummins that kept snapping studs on the manifold, three in one week. My lead tech watched me fight it and said 'you ever lube the threads before you torque?' I always thought oil changed the reading, but he showed me the book spec drops by like 15 percent when you use the right anti-seize. Ran a torque wrench over a clean thread versus a lubed one on the bench, the difference was real. Now I hit every exhaust bolt with a thin coat on install, zero comebacks since. Has anyone else avoided this trick for years then felt stupid when it clicked?

1 comments

1 Comment

janac5124d ago

The part about the book spec dropping by 15 percent with anti-seize is close, but it's not really a blanket number. That changes a lot depending on what kind of lube you use and what the fastener is made of. I've seen some specs that say you need to back the torque off by 20 percent or more with certain thread compounds, especially on bigger stuff like head studs. The real trick is to check the specific anti-seize manufacturer's chart for the fastener size and material, not just assume one percentage works for everything. Your bench test proved the point, but the book number is a starting guess, not a rule.