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Watched a new guy torque a spark plug to 90 ft-lbs and I almost walked off the line
Last Tuesday we had this new A&P student shadowing on a 737 engine swap. He grabbed the torque wrench and cranked one of the spark plugs down like he was tightening lugnuts on a truck. I caught it at 90 ft-lbs before he moved to the next one. Spec is 30 ft-lbs max on those plugs and I've seen stripped threads ruin a cylinder head in under 2 seconds. This is basic stuff but people cut corners when they're nervous or in a hurry. How do you train new guys to slow down and read the manual before touching metal?
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jordan_young26d ago
My buddy Dave snapped a head bolt clean off on a Cummins once because he was using a Harbor Freight torque wrench that had never been calibrated. Thing was clicking at like 70 when the spec called for 55 and he just kept going. We found out later that wrench was off by almost 20 ft-lbs from the factory. So now I tell every new guy to treat their torque wrench like a loaded gun, check it against a known good one first or at least listen for the click on a scrap bolt. But that spark plug story makes my teeth hurt, aluminum heads are no joke and 90 ft-lbs is basically a death sentence for those threads. I've seen guys strip them just by getting in a hurry with a ratchet, never mind a torque wrench set to truck wheel torque.
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sammoore26d ago
Yeah, I read somewhere that torque specs on spark plugs are often way tighter than people think because of how soft the aluminum heads are. You'd think after the first horror story in the shop, everyone would double check.
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