Contour Enthusiasts Group Archives Forums General Troubleshooting spark plug has stripped

I'd phone around to find a shop with expertise in doing the job without removing head. Metal cuttings from the re-tapping of threads do pose a risk to engine health when the fix is done "in-situ", but that's what an expert would deal with by preventing and/or removing.

Any shop could do the job with head removed and if your willing to go to that expense then total engine replacement (with a used one) becomes economically viable (considering your mileage). I would guess about $750 for used plus $1000 for installation.

p.s. I presume valve job estimate you already have is for both heads.