stripped spark plug thread

[jerry-ahrens]

I’ve always used red Loktite on the spark plug inserts, never had any issues. I put one of those in a Chevy Cavalier 2.2 4 cylinder, probably 10 or 12 years ago. I broke off a spark plug trying to remove them… man what a mess! I used an air powered hacksaw to cut slots in what was left of the old spark plug, then picked it all out with a magnet. I rolled the dice [big time] and installed the heli coil spark plug repair (with a well greased tap) insert with the cylinder head on the engine. After all day working on it, I was aggravated, and figured it would either blow, or work! It’s been running great ever since ! I know I lucked out big time !

[oltimer]

I agree with you Jer and Mumbles with the use of "Save -A-Thread" product. Using proper tap oil when cutting the thread, and the use of Electronic Cleaner to clean all oil residue before installation is a must. The use of Loctite and the proper seating tool is a must; as I have never have one back out or failure with years of use, and many plug changes also on the same insert.

[garry-in-michigan]

Nice try Frank . . . 🙂

[Mumbles]

quote OLCAH:

The head did not tap well. The tap tore the aluminum head material without cutting clean threads. The head is quite thin so the tapped thread was short. The insert just pulled out.

Something went wrong here, big time. The supplied tap in the kit has a pilot thread on it and will follow what’s left of the original threads, if any, before the wider section cuts the required thread for the insert. The pilot ensures the threads are going to cut at the same angle to the head as the original ones were. This should have been a plug and play type of operation and the threads shouldn’t have failed.

[olcah]

Yes, The tap was new out of this package. I am no expert on tapping but I have tapped a lot of holes so go gently. Immediately I noticed that the material was not cutting cleanly but tearing in a gummy way. I tried to clear the tap and then continue but the tapped threads were terrible. I have not always had good results tapping aluminum especially die cast. Only thing I can think is maybe the tap is defective or the diecast material composition does not lend itself to tapped holes. I know that sounds strange. I did start the pilot in the remains of the threads. It followed them. Started cutting dry then tried lubricants but as I went forward tap continued to tear the material.

I appreciate your comment. Frustrating experience but we don’t win them all. 😀
Charlie

[rudderless]

I have fixed several old snowmobile motors using a 3/8npt steel nipple. I tapped the inside of the 6" nipple on one end. I cut off the thread on the nipple off the same length as the head is thick. Used a sharp pipe tap to cut new tapered threads in head, use oil . Stop tapping when the nipple is one thread short of threading fully in by hand. Degrease both parts. Thread on an old plug, no washer on to repair insert. Use locktite or even 518 sealer on insert. It should make up in one turn tight with a wrench on the plug.

If the motor overheats bad the insert might come loose but can be resealed after the event.

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