TIL I've been overtorquing injector hold-down bolts for 10 years

I used to crank those injector bolts down as tight as I could get them. Figured tighter was always better on a diesel. Then a senior mechanic at a shop in Denver last month showed me the torque spec for a 6.7 Cummins is only 22 ft-lbs. I pulled out my torque wrench and realized I had been doing probably double that for a decade. Now I actually look up the spec for every job and don't just guess. Has anyone else found out they were overdoing it on a common bolt and felt stupid about it?

3 comments

3 Comments

taylorshah1mo ago

The 6.7 Cummins injector bolts are a perfect example. I helped a buddy swap injectors on a Ford 6.0 Powerstroke a few years back, and his manual called for 18 ft-lbs for those hold-down bolts with a simple torque-to-yield procedure. He had been cranking them to 30 or 35 because he heard "tight is right" on those forums. We had to replace two bolts that had stretched and cracked the casting on the head. It's a good rule of thumb to always check the spec, especially on anything newer than 2005, and to use a torque wrench that's been calibrated within the last year. A lot of guys think they don't need one for smaller bolts, but cracking a head is a much bigger headache than buying a decent wrench.

kelly3851mo ago

Actually the 6.7 Cummins is a Dodge/Ram engine, not a Ford. Ford uses the 6.0 and 6.4 Powerstroke. But yeah, your point about people overtightening injector bolts is spot on for any diesel.

west.richard1mo ago

Man I've seen that exact thing happen more times than I can count. Had a buddy crack an injector bore on a 6.0 a few years back doing the same thing, thought he knew better than the torque spec. Cost him a whole head job and he still won't live it down.