Was using the wrong torque wrench on spark plugs for 3 years

I always thought my torque wrench was good enough for installing spark plugs on GA engines. Last month at a shop in Wichita, a senior mechanic watched me tighten one and asked if I ever calibrated it. I said no, figured it was fine out of the box. He ran a quick test and showed me it was off by 12 ft-lbs at the low end. I had been overtorquing plugs for years without knowing it. Anyone else ever skip calibration and regret it?

2 comments

2 Comments

wesleypatel1mo ago

Wait, is it really that big of a deal for spark plugs though? I mean, yeah it matters on head bolts and stuff, but a few extra ft-lbs on a plug can't be that bad, right?

bettyhunt1mo ago

Funny you mention this lol. I had a buddy who ran a small shop and bought a bunch of torque wrenches off some online sale. Never checked them once. We were working on his Jeep and he was torquing the head bolts with this ratcheting one. I asked him when he last calibrated it. He said never. So we tested it against my beam style one at home and it was off by almost 15 ft-lbs on a critical bolt. That coulda been a disaster. Now I test mine every spring with a known good wrench just to be safe.