Pro tip: Stop over-torquing spark plugs on Lycomings

I spent 3 years cringing every time I pulled a plug on a TCM 470 because the threads looked gnarly. Figured it was just old engines being old. Then I watched a senior A&P at my shop in Phoenix grab a torque wrench and set it to 300 inch-pounds on an O-360. He told me I was cranking them down like lug nuts on a Dodge. Now I check my torque wrench calibration every 90 days and my plugs come out clean. Anyone else get told they were way too heavy handed when they started?

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wells.amy5mo ago

That thing about trusting the wrench is spot on. I used to think a good "grunt" was the sound of a proper seal, but then I saw what that did to the helicoils on a Continental IO-550. Switched to a split beam torque wrench for plugs specifically and it changed everything, plus I stopped getting those little silver shavings on the threads.

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markl755mo ago

Ha, yeah I was definitely that guy. I used to tighten plugs until my arm said stop, wondering why they looked like they fought a belt sander on removal. Now I just set the wrench and trust it, way less embarrassing for everyone involved.

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