Help helicoil not working

62super

New User
So I picked up a 62 super major that is in really good shape. Blew some white smoke and I beleived to be a headgasket issue. After pulling everything apart turned out one of of the head bolts was stripped. Started thinking about options and rather then oversize it thought I would try the Helicoil route.
Took the bolt to the local dealer, and picked up the right kit supposedly 1/2" #20). Drilled the hole 33/64 and inserted the corresponding tap. Went to insert the helicoil and it was a little harder to turn in then expected. Put the bolt in and it mashed the threads and pulled the helicoil out I also think it messed up my original drill and tap job. Did I do something wrong? I haven't ever put in a helicoil before.

So what do I do now? Oversize it or try another helicoil? Anyone had a similar issue.?

Thanks,
 
First of all, if you have never used one before, as you already figured out a head bolt hole in an engine block is not the place to learn how to do it. There is a special tool to screw the insert in with, did you use it? They screw them in from the bottom instead of the top and they go in a lot easier. I would never use a heli-coil on a head bolt. There are thread inserts that are much heavier and better suited for that application. Only problem with them is they are thicker and sometimes there is not enough clearance for them. If you screwed up the new threads enough that another heli-coil won"t go in then you are limited to three options. Go with the next bigger bolt or use a thread insert that is for the bolt you have. The last resort is have the hole welded and redrilled. The thread inserts also have their own special installation tools you would need to buy if you go that route.
 
I don't know how deep the hole is but if it is deep enough you can put one in and screw annother one on top of it to get more threads to pull on!
 
Mole, not first the time doing something like this. Like I said I was planning on oversizing or the weld option as the other person suggested. I have a background in machining and actually put a coil in a buddies street bike a few years back. Went off without a hitch.

Basically I did the same thing and used the insert tool. You can insert coils from the top down also. Thought this would be an easier way to fix things.

Right now I am trying to figure out if anyone has had a similar experience or what in the world has gone wrong.
 
Just to let everyone know I got things sorted out. New set of coils and everything is alright. something was wrong with the original ones I had. thanks for the replies
 
what do you mean you can't stack them, i have used 2 and 1/2 coils in a block once, I did this in 3 holes on the front of the block that holds the front end on, i used 5/8 grade 8 bolts and really tighten them down trying to strip out the helicoil out. that has been 16 years ago and the tractor has a loader on it and never a problem. I have stacked coils in other places and had no problems,
 
Helicoil's are a bad idea for a head bolt. There's just too much pressure. Threaded inserts are available from industrial supply houses that can stand the pressure. In the old day's you would drill and tap to a larger size, bore a hole through that size bolt an inch or two, screw it in and you were done. It's a lot nicer being able to buy them.
 
"Helicoil's are a bad idea for a head bolt."

WHAT gave you that idea?

Been listening to old mechanic's wive's tales again???
 
I agree with Bob. I've used helicoils in many high stress situations and never a problem. I've also stacked them one on top of another. Just reach in and break off the installation tab and pick it out with a small pencil magnet if you are working in a blind hole. The only thing that will not work is putting a Heilcoil inside of a Helicoil as "Won't Work" said. Dandy Dave!
 

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