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Old 06-06-2017, 08:44 AM
mjbrox's Avatar
mjbrox mjbrox is offline
Join Date: Jun 2008
Location: Golden CO
Posts: 1,546
So last week I cross threaded a park plug. Not too deep, but probably two full revolutions. As any sane person would, I freaked out. I looked at thread chases but they seemed like you could mess it up even more, and push metal shavings into the head.

So after some searching I found the

Powerbuilt 640811 14mm Back-Tap Thread Repair Tool

Basically you insert the tool into the head, expand the threads and back it out.

Even with the threads retracted you can lightly thread it in. Once reasonable deep I expanded it and then backed out. I probably did over a dozen passed. I was being extremely careful. I also kept the tool covered in grease to catch metal filings

The results were, I was able to easily thread my plug all the way down by hand before torquing it down

These don't appear to available in stores so I had to have Rover down all weekend while I waited for the tool.
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Old 06-06-2017, 11:27 AM
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squirt squirt is offline
Join Date: Nov 2008
Location: Los Angeles
Posts: 785
I've used this before, bought mine from Amazon. Cyl #8 spark plug threads on a D2 were bunged up, and the spark plug was only about 2 threads in (forced/cross threaded) when I got it. Trying to chase the threads from the outside was hopeless, as they were destroyed. This thing was slick as hell, just want to reiterate that you need to grease it up to catch all the filings that come off. 3-4 graduated passes did the trick for me.

Worth every penny.
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Old 06-06-2017, 12:07 PM
mjbrox's Avatar
mjbrox mjbrox is offline
Join Date: Jun 2008
Location: Golden CO
Posts: 1,546
Oh yea. I did 12 passes or more. I used fresh grease on every other pass
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Old 08-07-2017, 08:54 AM
WaltNYC's Avatar
WaltNYC WaltNYC is offline
Join Date: Mar 2010
Location: NYC
Posts: 396
Member Trucks
Good stuff. Thank you for posting this. #8 cylinder can be a pain. Some spark plug sockets don't fit very well. The exhaust manifold gets in the way.
1997 Discovery I SE - 160k miles

RAVE in pdf:
Discovery I exploded parts diagrams....
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Old 03-08-2018, 12:00 AM
ROAMer ROAMer is offline
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Join Date: Feb 2018
Location: Michigan
Posts: 2
Member Trucks
Ditto. Saved money, time and trouble. i also bought the $25 Amazon one. However, there are better ones which might be worth it now that i know the experimental effort worked so well instead of Helicoiling or more intensive options.
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