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Caught a guy torquing spark plugs on a cold engine yesterday, here is why that's a problem
I was walking past a bay at work yesterday and saw a new guy zipping spark plugs into a cold Continental IO-520. He had the torque wrench set to the book spec and everything, but the engine was probably 50 degrees from sitting overnight. The problem is the aluminum head expands when it warms up and the plug gap closes up, plus the torque values are for a warm engine. I told him to run it up to operating temp first, let it cool down just a bit so he doesn't burn himself, then torque them. He looked at me like I was speaking a different language. Has anyone else had to explain this to a new mechanic or am I just getting old?
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miles_young598d ago
Hold up, you just blew my mind. I've been turning wrenches for almost fifteen years and I always figured the gap changed with temperature, like the electrodes expanding differently or something. So it's just the threads being dry versus lubed that messes with the torque reading? That makes a lot more sense actually, but why does every old-timer I know swear by warming it up first? Are they all just stuck in their ways or is there something else to it?
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miles_young598d ago
Actually the gap doesn't change with temp, the real issue is the threads being dry.
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