.....Well, I hope I didn't blow it big time, this time! I was pulling an engine
out of an old car I have in my back yard. One of the spark plugs was
really loose in the plug hole & I didn't pay much attention to it. When
pulling the engine the headers that were still in the car but unbolted from
the engine must have banged against the plug and messed up the threads {this is all I can think of that could have done this}.
Now the plug won't go into the hole {I forced it a little even, I know, bad idea} & I can see where the threads are
messed up. Just appears to be at the very beginning of the thread {hole}. Can I run
a tap through it {and if so, what size is it?}. It seems to me as if the best
thing to do would be to pull the head & tap it from the back side. Because the
threads at the back are good {& this would at least start the tap off straight}. I DON'T want to take the head off though! Oh, they are AFR aluminum heads..... Any ideas??? Thanks a bunch ... Bill....

 

Should be able to helicoil it.

 

...Eric, THANKS A BUNCH! .... yeah, I've heard of heli-coils but never
really knew what they did. I did a search on the web for 'heli-coils' and
read about them. But do you think I'd be ok to do this without taking
the head off??? I'll just have to make sure that I get ALL the lose material
out of the cylindar, correct???
thanks, Bill....

 

You can get thread chasers to clean the threads up. Just make sure you blow the cylinder out with air to get any filings out. I would roll that cyl up to TDC so nothing will fall way down in there. No sweat.

 

....Thank You Scooter.... Bill...