359 Spark Plug Threads Stripped

Posted by Don Shields On 2015/6/10 13:44:51

A problem has developed with my 359 aluminum cylinder head. When removing #3 spark plug, it came out with a sleeved insert attached to it that had a fracture in the sleeve's bottom two threads. This assembly will not screw back on, I'm sure the fractured thread section did a number on the head's threads. Any thoughts on how to deal with this? I'm not sure a new sleeved insert would hold in the head and likewise with a helicoil. It looks like the hole in #3 is at least 16 MM in diameter. I'm wondering how advisable it would be to retap #3 to accept an 18 MM spark plug. Or are there any other repair options available? Comments and suggestions, please.