Nemo
check the helicoil for temperature resistance. Going down inside a head so close to the combustion chamber is going to be pretty extreme heat.
Also, in order to get them to have the correct inside diameter for the plug to fit into, you know you have to drill out the existing hole and then tap it for the new helicoil to thread into right?
Where do you suppose all that metal from drilling and tapping is going to go????
I think you're pulling heads off no matter what to do this and if you are going to do that, I think you might want to check cost of replacement set, even used set that should likely be machined to be safe.
Expensive? Yep.... But think of the additional mileage your vehicle would likely get from doing it correctly...
PITA??? Yep... But you are getting pretty good at this mechanic stuff. You have more ambition than me...
This is all just MY OPINION and a suggestion for you.
It was free and I realize you did not ask for it.
SO, good luck to you with your project but I always go by the rule that if something is worth doing, it is worth doing correctly. The end and long term results are always far better than shortcuts..
Best,
micro...
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