Tried a Heli-Coil for the fist time

Sat Jun 12, 2004 10:06 pm

While reassembling Missy yesterday I realized the threads were weak in one of the oil pump cover bolt holes. Tried a longer bolt in it, but it still felt soft. Not enough room for the bolt head if I drilled and tapped it for the next larger size unless I used a socket head bolt. Checked with the local auto parts store, and they had the NAPA version of the Heli-coil. Expensive little bugger. $24.95 for 10 inserts, the installation tool and a tap.

I put some small refrigerator type magnets below the hole to catch the cuttings and went to work. Drilled the hole out and used the tap to cut threads for the insert. Cut one of the magnets up in strips so I could slide it into the threaded hole and get all the cuttings out. I also decided to use a drop of Loctite on the insert when I put it in. When I looked it over after the install, I thought "There's now way that little thing will work!". But it did. As a matter of fact when I ran a new bolt into it I couldn't feel the difference between that one and the undamaged ones.

Hopefully I'll get the dirt scoop on and the paint touched up in a day or two and then will post some pictures.

Sat Jun 12, 2004 11:00 pm

I tried one the other day too. Got it at napa. I was going to repair the stripped threads on my carb. So i drilled it with the correct size drill. Used the tap, and tried to put the insert in. I couldn't get the insert to go in. I tried for over an hour, and it didn't go in. It just wound up on the insertion tool and then stretched out. Any Ideas what I did wrong? The newly tapped threads looked like they were good. I cant figure it out.


EDIT: I also checked and made sure all the parts in the kit were the correct size.

Sat Jun 12, 2004 11:14 pm

I've only used one this time, but it went in just like turning in a bolt. , then I backed the tool out. You did insert the tool through the insert before trying to screw the insert into the threaded hole didn't you.

Sat Jun 12, 2004 11:36 pm

Yes, I put the insert on the tool first. I did read and follow the instructions. It just wouldn't turn into the threaded hole. Also in the instructions, it said something about putting the insert on and into the slot on the tool. My tool didn't have a slot. Did yours? I tried it without, then I used a hacksaw and made a slot to hold the tang, and it still did the same thing.

Sun Jun 13, 2004 9:38 am

The installation tool that came with mine didn't have a slot. It was threaded similiar to a screw, and the end had a shoulder that the tang on the insert caught on when you screwed int into the insert. It all went together very easily. Your description makes it sound like the inserts or the tap were either the wrong size, or the wrong thread pitch. The tap for different pitches would be different, as well as the insert. Wonder if they mixed the insert and tap pitch in the package.

Sun Jun 13, 2004 3:31 pm

The tap is a special helicoil tap for your particular size bolt. It will just be a larger diameter than the regular size tap. (Should have come with the kit) I found a slight chamfer (counter sink) helps start the insert in. Sometimes they are hard to start but if everything is the correct size, they eventually will start when lined up perfectly. The end of the insert tool should have a step in it to drive the helicoil by the tang. You can use needle nose pliers to break the tang off after (or drive a pin through the hole) if you don't want it there. Also, to replace the helicoil at a later time, use the needle nose to pull the old one out. Now that you have the kit, you just need to buy the inserts next time. Much cheaper. Hope this helps.............

Mon Jun 14, 2004 5:57 am

I agree with Ron. The countersink helps. If nothing else thanm to remove burrs. I have had burrs hold me up when trying to start the blasted things, the countersing can help.. Just curious, does the NAPA kit tell you to use Loctite on the insert?

Mon Jun 14, 2004 7:37 am

Carm. Don't know if loctite is recommended or not. With blind holes I don't think it is necessary if the insert bottoms out. However, on thru holes, I always use loctite to prevent the bolt from screwing the insert out the other side IF the bolt is a tight fit...........

Mon Jun 14, 2004 1:12 pm

The NAPA kit doesn't mention Loctite, I decided to do that on my own.

Mon Jun 14, 2004 1:58 pm

There is one brand that calls out loctite, I just cant remember which

Mon Jun 14, 2004 3:32 pm

Most Heil-Coils I've used will not back out once the tang is removed, but loctite will never hurt and is good insurance.

Mon Jun 21, 2004 7:36 pm

Carm wrote:There is one brand that calls out loctite, I just cant remember which


Probably whichever brand also makes Loctite.

Mon Jun 21, 2004 8:22 pm

Installed many heli coils 25 years ago into Radar High Voltage units. Mil Spec required that Locktite be used. Can't remember type or details.
Use of Locktite can't hurt.