anyone ever had any experience with these? 14mm is the correct size for these motors, right? im thinking about it as a last ditch effort before resorting to helicoil and/or head swap. all the threads are fubared on this ****in truck but #6 is missing a good deal of threads on top, but the cylinder side half still looks usable... i just cant get to em lol and id ont want to strip anymore threads out jsut to get to them as a traditional chaser is doing.

Reverse Action Spark Plug Thread Chaser 14mm

 

You are trying to pull injectors plugs without removing the upper intake manifold and not you are trying to repair damaged spark plug threads without removing the heads.

I think you need to take a step back and look at a big picture, or post what you actually have going on for some sanity checks here.