Lotus Elan

Spark plug insert

PostPost by: englishmaninwales » Sun Sep 08, 2019 1:22 pm

Oh what joy, on removing the no 4 spark plug this morning, it came out with it?s insert still firmly attached... So...What to do?
The thread in the cylinder head looks ok and the combo easily screws back. The threads on the insert have some very small witness marks 180 deg opposite each other, so not the first time it?s been out, me thinks!
What is the best way to deal with this, both short term - car is used a lot this time of year (use thread lock?) and proper fix long term?
Thanks
Malcolm
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PostPost by: Mick6186 » Sun Sep 08, 2019 1:58 pm

Blue Loctite on the insert & copaslip on the plug thread. Leave for a while to harden.
Worked for me.
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PostPost by: 2cams70 » Sun Sep 08, 2019 2:04 pm

These are the best inserts for spark plug hole repair. Forget Helicoils for this application.

http://www.lnseurope.com/index.php?opti ... 64&lang=nb
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PostPost by: nmauduit » Sun Sep 08, 2019 2:17 pm

was the engine cold when you removed it?

if the insert can be removed from the plug (if it does not go easily I would not insist) I would clean up everything first, the lightly lubricate the plug (I use copper grease). You may want to play with heat if you are set to try your best to remove it (assembly in the freezer then heating the insert), will help free the galling, too, plus WD40 etc.

then short term I would try glueing the insert back in place with epoxy (one or 2 part, depending what you can find, some handle heat better than others), trying not to put too much so that excess may not cause a problem in the chamber. Caution to the depth of insertion in case the insert is not limited by a seating (you may add extra washers if you managed to remove the insert from the plug, so that you have a better control of the seating. Don't over tighten it.

After curing, you may be able to remove your plug if you hadn't been able to previously : apply some copper grease to the thread, then don't overtighten it (I usually seat it by hand, then only do a fraction of a turn holding the tube wrench by the tube not to apply too much torque). I prefer risking it not being torqued enough than overtorqued, and check them regularly so it's easy to find the torque level that holds (I apply copper grease every other time, the plugs always go down to the seating just with the fingers).

If the insert stays once glued it can last as long as the engine under normal conditions - then longer term would be head off first (for an other, better insert, of weld and re-tap etc).
If you have events scheduled shortly don't take chances if it does not go out reasonably easily after curing in case you did not manage to remove the insert before glueing it back, a couple heat cycles (plus WD40 from the top) may help freeing it and in any case you can use your car in the meantime.

good luck !
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PostPost by: englishmaninwales » Mon Sep 09, 2019 11:23 am

Thanks for all the advice, job done. I couldn?t get the insert off the plug, so degreased the threads on the insert and as best I could in the CH, and put the plug/insert back in yesterday (I used blue Loctite) and today the plug happily unscrewed. All plugs checked and refitted with Copperslip.
I have always been careful about not over torquing plugs, but hopefully the insert will stay tight until the head gets an overhaul.

Malcolm.
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