Rant: Stop torquing spark plugs cold on radial engines

I was helping a buddy swap cylinders on his R-985 last weekend and watched him torque all 18 spark plugs to spec with the engine ice cold. Had to stop him and explain that the manuals call for hot torque on these because the aluminum expands different than the steel. He argued with me for 10 minutes until I pulled up the Continental service bulletin on my phone. Anyone else run into mechanics who skip the hot torque step on radials?

3 comments

3 Comments

nina_campbell27d ago

Gotta admit I used to be one of those guys who torqued everything cold. Then I rebuilt a Jacobs R-755 a few years back and had two plugs back out after the first run. Scared the hell out of me when I found them sitting loose. Now I always run the engine for a few minutes and retorque them hot, even if it means burning my knuckles on the cylinders. Do you ever just mark the plugs with a paint pen to see if they move after the hot cycle?

lee_reed27d ago

Stripped a knuckle or two myself learning that lesson the hard way, lol.

matthewmartin27d ago

Yeah, paint pen works but you gotta make sure the cylinder is clean first.