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Wed Jan 12, 2005 9:16 pm

I tapped a stripped spark pug hole to 18mm and got a screw in insert. It works fine but every time I take the spark plug out the insert comes with it. What is the proper way to secure the insert into the head so that it stays. Should I put some thread lock on the threads of the insert? How about muffler cement?

Wed Jan 12, 2005 11:05 pm

Okay, I'm no mechanic but no one has answered so here goes. Clean the insert and the head real well. There is an adhesive for this use (forget the name...but any parts store). Apply to the insert and instal. Use a heat resistant lube on the spark plug. Again, any part store will know what you need. Good luck.

Fri Jan 14, 2005 4:39 pm

I've had this problem before, i tapped a new hole, and put the insert in with thread lock, once that plug is put in try not to take it out if ya dont have to, when i did mine, the engine ran for about 3 weeks, then i was going up a steep hill and the plug shot out resulting in my cylinder head being melted along with the spark plug. after that i got a new bug and new motor, the bug was very rotten so.....

I recommend buying a new head if you can find one for cheap.

Fri Jan 14, 2005 5:19 pm

Use Locktite threadlocker on the insert, then dab a bit of motor oil on the plug threads. The Locktite should hold the insert and the oil will keep the plug threads from seizing, allowing for easy removal.

Fri Jan 14, 2005 6:10 pm

As long as you can change plugs by changing the insert with the plug, it really doesn't hurt to have it come out. I'm not sure epoxy can hold it in with the high tempertures. I'd hate to have the epoxy melt and get in the cylinder. May mess up the rings. I'm not sure.

As a machine shop. You may be able to get a spark plug with a larger thread daimeter.

Sat Jan 15, 2005 7:54 pm

Been there buddy, and I feel your pain.

I've tried just about eveything to keep those inserts in. JB Weld, Green Loctite threadlocker, etc.

My first VW ('71 Super) had an insert that came out with every plug change. I figured it would be fine If just kept screwing it back in. NOPE, didn't work - One day on the freeway the plug blew out of the hole. That plug hole was pretty much stripped out for good. But, I nursed it along for 3 more months by JB Welding the spark plug with insert to the head. When your a poor High school student JB weld is your best friend : )

Bought a set of rebuilt heads for an engine I was building for my '63 Bug. They had an insert in one plug hole with Green Loctite threadlocker holding it in place. The first time I changed plugs on the engine the insert came out on the plug.

I built a S/P 1600cc for my Daily Driver '66 Bus about 4 years back. I picked up the head cores at a swap meet, and one had an insert in the plug hole. It was tight, but I still didn't trust it. So what I did when rebuilding the heads was screw the insert in a far as I could and then on the chamber side I peened the insert into the aluminum of the head.

I ran a 6 volt system with this engine and seemed to have to change plugs every 6,000 miles. Never once did that insert come out on me.

I'm convinced it's the way to do it, but it can only be done with the engine apart...

Tue Jan 18, 2005 5:08 pm

Here is one advice I can give you next time you change a plug.

If it feels like you are stripping it, YOU ARE!

Tighten the plugs ..just snug. It is NOT an axle nut. :lol:

The thread repair kit has a staking drift to somewhat expand the insert and keep it in place. Just be careful when you hammer the drift in against the insert.

I like this insert style better than the helicoils.

I would not put too much dab of sealer and other glue you are thinking about putting. The plug has to have good ground to fire and be effective. You can put too much goop there that you might isolate the plug and have misfires. Now this you do not want.

There will be a point that you just have to let go the heads when they are really old and buy a new set.

Good luck.

NSR.