Helicoil installation

[BDA]

As those who have noticed my thread on "ring and pinion lash" know, I've taken my tranny out and the bell housing off the tranny. I thought I'd take the opportunity to install helicoils in all the threaded holes where the bell housing mounts to the block and the tranny. Having never done this before, I ruined the first helicoil. I think the problem I had was that that I did not cinch the collar to the helicoil and that allowed the helicoil to cross thread in the casting. When I locked the collar down to the helicoil (see first attached picture). Things were going pretty well till I noticed that two of the threaded holes are counter bored (see second picture). Obviously, the counter bored hole presents a problem because the collar won't fit in the counter bore.


Does anybody have any tips for installing a helicoil into threads into a hole like this?

[jbcollier]

Why are you fitting helicoils?  Are the threads pooched?

[BDA]

I pooched one set of threads and figured while it was apart, I'd fix the bad threads and make sure that I'd be less likely to pooch any others. I have two different kinds of install tools. One that is threaded which would would work well for this application, but unfortunately, the installation tool I have for this size is not threaded.


I can live without it, but it just seems like a great time to do this if I can.

[jbcollier]

Don't do them all unless required.  As long as you don't use an impact gun, there won't be a problem.  If you are careful, you can usually wind an insert in by just the tab.

[rascott]

i keep buying these kind of kits.
https://www.amazon.com/Helicoil-5521-4-Coarse-Thread-Repair/dp/B0002SRE8Q/ref=sr_1_13?s=automotive&ie=UTF8&qid=1491025657&sr=1-13
i get them at the local auto shops and good hardware stores, and they work well.
i see your insert tool has a shoulder ring/adjustment thing i'm not familiar with.
perhaps chasing the threads w/appropriate tap may clean the existing holes well enough?
i don't see the step as a problem...........u'd be drilling oversize for the tap, but the threadsert should fit.

[BDA]

Thanks, rascott and John. It's too late to take your advise, John. As I said, I had at least one set of threads ruined without consequences, but I just got a bug up my butt and thought the abundance of caution was worth the hassle.


I got the last two helicoils in. I used a piece of tubing to go between the helicoil and the collar which allowed me to screw in the helicoil and maintain pressure on the wire to keep it from getting deformed (what I learned was the purpose of the collar). In essence, I had a skinnier and longer collar. The install tool you have, rascott, is like the one I have on my 3/8 - 16 helicoil. Since you screw the helicoil on the tool, the threads support the wire and keep it from being deformed - probably a better type of installation tool since it works no matter how deep below the surface the threads start.

[buzzer]

Not sure the collar really does anything much, I will check on on my helicoil set. As the tang (the bent bit at the end) pulls the coil in if the collar puts any pressure on the coil it would have a tendency to expand the coil and make it difficult to fit. The collar is there basically to act as a stop, but you could do it by eye. I would also agree, no need to helicoil unless to need to. I have fitted a few in the head for the exhaust and in the timing cover.

[BDA]

I have assumed the collar keeps the wire to follow the threads in the piece because I didn't use a collar on the first hole I did. Some of the wire cross threaded the tapped threads. I didn't have that problem after I set the collar against the wire when I installed the rest of them. Could be coincidental.


I agree that helicoils are not absolutely necessary. Since I had at least one hole stripped, I figured it made sense to make it harder for that to happen again. I seem to take my car apart a lot.