Spark plug hole crossthreaded

[benemorius]

Aluminum head + agressive friend - patience = crossthreaded sparkplug

This is on my project car, which is currently in line for a rebuild, so I'm in no hurry. I'd just like to know what I can do about it. He managed to get the plug in all the way, and it actually seems to seal. I guess it's not 100% broke if it works, but I still want to fix it. Options?

[navysnail]

drill it out and use a helicoil

[Scott McLellan]

NOOO!!! No helicoil for this! I can't remember where I read this, and I might just be making this up but I don't think it's a good idea. I think it messes with the dissipation of heat or maybe the electrical grounding of the plug or something. My memory might not be right on this but ask and experienced mechanic to confirm before you believe me.

And if you do drill it out your going to need a way to keep the metal shavings out. Maybe coat the bit in grease and drill a little at a time??? Or maybe take this question to an experienced machine shop guy.

[s13sr20chris]

remove the plug and run a chaser down the hole. hope, that it works.

[devonhynes]

Scotts right don't use a helicoil for this. Did the same thing to a engine in shop class at school. Get a tap with the same thread and try to fix it that way.