thank you all for your advice.i greased the tap to catch most of the shavings,turned the
motor over with plugs out,put the helicoil in and installed the plug with no problems.
engine runs fine,will bring more money now. not scared,just wanted to do it right.
thanks again,

 

glad it worked out for you

 

Good job! I was just joking around about the scared comment. Some people would not even try what I suggested you do. They live by the better safe than sorry rule. I also live by this rule and I know this to be a safe way to do it since I've done it a few times and I was not sorry, LOL. An old timer showed me how to do that in Clarksville Tn. Now you have one more fix in your resume.
Dave

 

thanks for the reply mopardave.i haven't tapped the hole yet,was just checking the fit
of the new plug to the helicoil.it slides in and out instead of screwing in and the helicoil
seems to about 1/8" larger inside diameter than the plug's outside diameter.thread insert helicoil

 

i have used them back when i raced. they thread insert,helicoil work good you should be fine. but you know you got to pull the head so shaving's dont get in the motor.

 

I quit using coil inserts years ago for spark plug repair, as did much of the auto repair industry. The barrel style such as Time-Sert stay in and seal much more reliably, though coil inserts properly installed are stronger than original threads.

 

Another approach is to take the head off and tap it to a 14mm plug. Call the tech line of your favorite plug company and ask for the number of a 14mm plug that has the same heat characteristics and properties of the 12mm you have been using. Once you have that number you can cross refernce on plug charts to find other Manufacturers plugs that will work.

 

I would put a lot of grease on the tap so the loose metal can stick to the grease.

 

I didn't see there was another page. Glad it worked for you!

 

The heli-coil is essentially a precision spring and if it is too close to the surface, the end of the heli-coil could be pulled out due to lack of support of the tapped heli-coil thread. thread insert helicoil