Spark plug blown out of hole

get an engineering shop to insert a helicoil or timesert.

I agree with Cheerful. Look on the bright side. You now have a nice air compressor to keep your tires properly inflated at all times! jor <

Solid thread repair insert like Tymsert, looks like a little cup, locks in place so it (theoretically...) can't spin out with the plug.

Can be done with the head in place if you have enough room for access, but the mechanic has to be really careful not to drop any shavings or crap down the sparkplug hole into the cylinder. And vacuum it out with a little hose when done to make sure.

You do not want a spring-style Helicoil repair, they're too weak for the application.

And from now on, use a little dab of anti-seize compound on the sparkplug threads, that's what it's for...

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You have a helicoil in your future, or a new head. The helicoil will cost about $10 bucks for a package of them, the head will cost a few hundred. Personally, I'd take a shot at the helicoil and hope it works.

PS Remove the remaining plugs and put them back in with some antiseize on the threads. My guess is that you did the last plug installation, and you were worried that you would damage the head if you put the plugs in too tight, the result being you didn't put them in tight enough. If you think you have an exhaust manifold leak, check the plugs first. I am thinking that you turned them in until they resisted, and added a quarter turn, or whatever, and stopped. If so, then you turned them in until they bound up a bit, but not because the crush washer had contacted the head.

Just be careful that the piston is not at the top. If it is you have a great chance of marring the top of it with the drill bit or with the tool used to insert the Tymsert. Also be careful of the valves. My brother chewed up a valve with the drill bit do this on his 22re motor. He checked for the top of the piston but didn't think about the valve hanging down.

Terry

Try installing a new plug. I have seen them vibrate their way out, and I have seen them vibrate si long, it wears out the threads. You have a