General vehicle thread

[Erni]

Helicoil is a diamond crossection spring. One side of a diamond goes into the new thread, the other forms the "old" thread. Keensert is a bushing/sleeve that is threaded on inside and outside. Generally it is bigger and thicker and once installed has locking tabs that get hammered in. Helicoils are held in by spring action.
Helicoils for assembly and limited in/out are fine. Multiple in/outs do better with keenserts. Keenserts will be a bit stronger because the outside diameter is bigger and thus they grab a bigger shear area.
If your plugs are taper sealed helicoils could be an issue. If your plugs have a shoulder snd crush gasket, helicoils should be fine.
Helicoils require a special tap, whereas keenserts use normal tap sizes.

[Irving]

Can one realistically drill and tap without filling the cylinder with metal shavings though?

[00tec]

Can one realistically drill and tap without filling the cylinder with metal shavings though?

Yes. Use a heavy grease on the threads of the tap. Clean and regrease several times while cutting threads. The grease will catch and hold the shavings. Use compressed air to blow out any others before installing plug.

[Erni]

Sort off. If you get a valve open and run a shop vac there should be enough suction to get most chips out during ops. After you are done with tapping I would probably use a small tube and vaccum in the chamber, and inspect.
Other way I could see doing this is by running the piston up higher to contol the chips and make them fall close to the center of the piston. Then vaccum with a tube, get the piston lower, inspect and revaccum.

[Erni]

How many miles on car?

[Irving]

I want to say about 140,000 miles. I was trying to use a straw duct taped to a vacuum last night just to clean up the parts from the exploded coil that settled on top of another plug. It wasn't working crap. I just plugged all the holes and blew the junk out.

Appreciate all the advice this far. It does seem like I'll still end up taking the valve cover off to access everything though. Oh yeah, that piston just so happens to be stopped very near the top already, so that's good.

[TFOGGER]

Timesert makes kits for doing these in place. That's what we use in the shop.

http://www.timesert.com/html/sparkplug.html

[Gman]

Wow, that whole operation sounds really sucky. Sounds like some anti-seize on the plug threads would have helped?

[Irving]

Wow, that whole operation sounds really sucky. Sounds like some anti-seize on the plug threads would have helped?

Unlikely. It blew the spark plug out of the hole while driving. Apparently its a relatively common Ford thing.

[00tec]

I did some kind of insert, but it wasn't a helicoil, dont remember the brand. This was about 15 years ago on my Taurus. Solid insert, used grease while tapping the hole. Put another 100,000 miles on the car without issue.