Not a fan of torque wrenches for spark plugs anymore

Last month I was doing a cylinder change on a Continental O-470 at my hangar in Burbank. Pulled out my trusty Snap-on torque wrench, set it to 300 inch-pounds like the manual says. Got the plug in and torqued down. Few days later, engine started running rough on taxi. Pulled the plug and found a hairline crack right where the barrel meets the insulator. Took it to the shop foreman, and he said it happens all the time with torque wrenches on spark plugs. Said the preset kind can overshoot if you don't go slow. Now I just use a good old beam-style torque wrench for plugs, takes a couple seconds more but feels way safer. Has anyone else cracked a plug from a click-type wrench?

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2 Comments

betty_white392mo ago

Ever had a beam-style wrench lie to you too?

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casey3932mo ago

Oh hey @betty_white39, switching to a digital torque wrench fixed that issue for me real quick.

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