Heli-coil Removal?

[Chris Trinkle]

Does anyone have any idea how to get a heli-coil out, that is in wrong? Was running a thread chaser in the spark plug holeand I didn't pay close enough attention to notice that there was a heli-coil in and the chaser started to pull it out. Long story short I put a new heli-coil in and the coil is cross thread for the first few turns(looks like coarse thread). Then it started to thread correct deeper in the hole. The beginning threads in the cyl. head are pretty shallow, but I can't get anything under the heli-coil to get it out. This is on a PA-12 w/ O-235 number 1 cyl. Any ideas would be much appreciated.
Thanks!

Chris

[Steve Pierce]

Chris, Aircraft cylinders use a serrated helicoil that is staked in. I have always been able to get a sharp pick under an offending heli-coil to get it out.
http://www.aircraft-tool.com/shop/de...UCT_ID=4260-18

[styoung]

Could maybe try.a left hand drill.of the tap drill size or thread minor dia. Size. That might back.it out

[Cub junkie]

Local heat to grow the aluminum cylinder head in the area of the spark plug hole, maybe. I think I'd rather pull a jug.

[SteveE]

Chris, Aircraft cylinders use a serrated helicoil that is staked in. I have always been able to get a sharp pick under an offending heli-coil to get it out.
http://www.aircraft-tool.com/shop/de...UCT_ID=4260-18

DANG,, You see the price on that baby!!

[mike mcs repair]

DANG,, You see the price on that baby!!

wowsa!!!.... theres a good reason to pull it and let one of the many local engine shops deal with it

[DesperadoPilot]

I did the same thing on a Harley Panhead cylinder head once. I just took an awl with a sharp point and pried the top thread leading edge out just enough that I could get a good grip on it with a pair of needle nose pliers, then I just twisted the nose of the pliers and peeled the helicoil out of the threads, slightly wrapping the helicoil around the nose of the needle nose pliers as I pulled it out. Once I started pulling the helicoil out of the threads and towards the center of the hole, it pulled right out of the hole in a spiral.

At this point I was able to re-cut the helicoil threads in the hole with the proper helicoil tap, but had to remove the cylinder in order to keep from dropping aluminum shavings back into the mounted cylinder from the tapping process.

Be advised that a helicoil thread is not the same as a regular tap thread. The inside and outside pitch of the threads are practically the opposite of each other so that when you put the sparkplug into the helicoil insert after the helicoil is installed, the threads will match up. A helicoil tap and a regular tap are totally opposite of each other as far as thread pitch is concerned.

[bob turner]

My Helicoil taps all look like fatter regular taps. The pitch is, and has to be, identical to that of the insert. Just look for the Helicoil label and you will be fine. Most of the time I insert my own Helicoils, using a tool for the finer threads, but I might be willing to let my cylinder guy do the sparkplug ones.

Beware of cheap imitations. Opinion.

[btracy]

Did you break the tang off the bottom? If not use some skinny needle nose pliers and pull the heli-coil towards the center enough to get a good grip on it then you can just pull it out like a spring. Otherwise some work with a dental pick till you can get a hold of it from the top end.

[Chris Trinkle]

Well I got it out. It's not pretty. I'm probably going to have to pull it and have the cylinder shop fix it correctly. It has a nice ding in it now. Thanks for the info. That's a really nice kit Steve. I've never used that one before, always use Perma-Coils with no issues. I need to pay attention more before I thread chase. Thanks again!
Chris

[12Geezer2]

DANG,, You see the price on that baby!!

How can PRICE be an issue with an Okie who hunts coyotes with a Gulfstream ?????

[Chris Trinkle]

Can a guy change from Perma-Coil to Heli-Coil? Will the taps be the same?

[Cub Builder]

ATS is mighty proud of their tool. I bought my 18 MM helicoil tool from NAPA for something on the order of $130 about 10 years ago (and I thought that was overpriced at the time!) I seem to have the only one in the area, so have replaced the helicoils in a number of aircraft cylinder heads. many with the cylinders still on the engine. Inserting the spark plug threads is quite different from the smaller helicoils in that the helicoil spring has to be compressed down inside the tool before screwing it into the tapped thread. It has a lot of spring pressure out against the threaded wall once it's in.

-CubBuilder

[Den]

I replaced one in Continental cylinder last month. I used an awl to pop the first thread and then twisted it out with needle nose. Used the Perma thread tap to clean it up. Blew air through the other spark plug and bore scoped the chamber for any swarf. Air will clean out the stuff pretty good- just make sure both valves are seated.

Had to do this one in place as it was about 12 hours to remove the cylinder as the motor mounts were in the way and the induction system was a nightmare (210T).

Glad to see you got yours out.

[qsmx440]

I replaced one in Continental cylinder last month. I used an awl to pop the first thread and then twisted it out with needle nose. Used the Perma thread tap to clean it up. Blew air through the other spark plug and bore scoped the chamber for any swarf. Air will clean out the stuff pretty good- just make sure both valves are seated.

Had to do this one in place as it was about 12 hours to remove the cylinder as the motor mounts were in the way and the induction system was a nightmare (210T).

Glad to see you got yours out.

I was thinking of commenting on this when someone said to "remove the cylinder" before cutting Helicoil threads. Anecdotal only and only motorcycles but when I owned my Honda dealership we used to put Helicoils in motorcycle (aluminum) heads all the time (hundreds) as Den described but with one thing added. We would always put axle grease on the tap and take a 1/2 turn at a time (where you can feel you are cutting) and retract and remove the burr from the grease, re-spread the grease and then go again. Never had a stuck valve or any problem. The cylinders were steel and any small pieces that may have found there way in their went right out. I personally would fly behind an engine done this way. I don't think a tiny aluminum chip could do as much damage as a hard piece of carbon breaking loose from the cylinder crown. WARNING: your mileage may vary. The only possible problem I think (besides the valve sticking) would be a piece getting past the rings and if that CAN happen you have larger problems with the cylinder than a tiny piece of aluminum. I wouldn't try this with a steel spark plug hole. Steel is a different story loose in a cylinder moving around in there.

[Chris Trinkle]

Thanks for all of the info! I ended up having to pull the cylinder and took it to Mid Valley Aviation in Los Banos. I walk in to his shop and he took it form me. So I walked around his shop looking at engine parts. 20 minutes later he came back with it fixed. Very pleased! It's back on now. Waiting for a carb heat box and she'll be going again. My brother is chomping at the bit to get his TW endorsement in the cruiser and build time for his commercial. Just got his private in July. Thanks again!
Chris

[SteveE]

How can PRICE be an issue with an Okie who hunts coyotes with a Gulfstream ?????

I had a good fur season last year!


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