Just figured out I've been over-tightening spark plugs for years after a customer's head cracked in my bay.

3 comments

3 Comments

Yeah that torque wrench is your best friend for spark plugs, especially on aluminum heads. Seen a few guys just go by feel and end up with stripped threads or worse. For most passenger cars, you're looking at like 15 to 20 foot-pounds, which is way less than you'd think. Hand tight plus a quarter turn with the ratchet is usually safe if you don't have a spec, better than cranking it down.

jakep2427d ago

Ever wonder why they make those little torque wrenches? I mean, that spec feels way too light, but it's there for a reason. I learned the hard way too, it's an easy mistake to make.

finley77717d ago

Remember it's not just about the threads. That low torque on a spark plug crushes the gasket or washer correctly to form a proper seal. If you over tighten it, you deform that seal and it can lead to a slow leak, misfires, or even a plug that blows right out under pressure. The spec seems light because you're only compressing soft metal, not fighting against a big bolt.