heli coil help

[herblove]

I just took off my exh manifold and I had 2 studs that were 10mm size that I had tap before when my 8mm studs had broken. Well I was going to put in the 8mm heli coils to make everything the way it was suppose to be. One of the 10mm hole was perfect so I didnt need to tap it for the 8mm heli coil at all. ( It fit right in no problem ) Now the other hole was stripped and would not tap using the size tap for the 8mm heli coil. It would not even tap to put back a 10mm stud in it. Now I have a hole to big for a 8mm heli coil or a 10mm stud I was wondering what can I do now. First thought is if I can find out what size tap is used for a 10mm heli coil tap. ( Its should be bigger that 10mm ) The next question is can I use two heli coil together. Like if I can get the 10mm heli coil to fit. Can I then put in the 8mm heli coil inside of it. If so would it be strong enough to hold a tight seal on the manifold? Basically I need to know what is the best option for me at this point.

 

[chadnum1]

time serts makes over sized sets for just this problem.

 

[herblove]

the problem is I dont know what size to get. Is it possible for some one to weld the holes up without having to take the head off I could then drill and tap the hole for the 8mm stud

 

[xloki77x]

By oversized, I think chadnum1 means 12mm OD helicoil with an 8mm ID. They do make them, however, I cannot recall who. Try Fastenal as well.

 

[herblove]

thanks for the replies. I going to try to make a reducer stud. I mean I am going to tap the head a 12mx1.75 and then get a stud and cut it so that I only use the threads of one side of it. Then cut a 8m stud and weld it to center of the cut off 12m stud. Thats the idea in my head right now. Hope it works because the welding shop said that my head would have to be off the car to weld the hole. (not enough room)