Strip spark plug

[SPYDERLK]

All you have to do to chase those threads is put some good old axle grease on your tap - and even if you were to get a tiny bit of aluminum in the cylinder, it will be gone quickly right out the exhaust valve.

Yes.

 

[SPYDERLK]

Always apply a small amount of never sieze to the plug threada no matter what engine they go in..Prpblem with chasing the threads with the head installed is you will get swarf in the combustion chamber and that is not a good thing.

Particularly necessary in aluminum heads. The Al/Fe differential expansion "works" the joint. A little piece of aluminum cracks loose from fatigue and follows the plug out, mashing and galling as it goes. Copper bearing antiseize is the best insurance I know of to prevent any Al from bonding to the plug.

 

[IH3444]

Repaired dozens of stripped sparkplug hole threads back in the 1970's while working at an independent Volkswagen repair shop. First you need to set the piston and valve timing so that the exhaust valve is open and the piston is below where the thread repair tool can reach. You sometime can just run a sparkplug thread chaser tool down the threads and clean them up. Blow compressed air into the sparkplug hole. This will make any aluminum fines go out pass the open exhaust valve. I also second the use of grease to collect the thread shavings, although it can interfere with the Time-Sert installation. Sometimes this works finds and sometimes the sparkplug will blowout after a time. Then you have to use the new thread cutter tap and the new full Time-Sert installation. We used to red Loctite the new Time-Sert into the freshly cut new aluminum threads so it would never come out upon next spark plug change.
When replacing sparkplugs, I put a bit of oil or grease on the threads. Even though it will cook off it still creates an interface between the metals which resists them seizing together. I think the older school lead anti seize is a good idea also. I had read that anti seize can cause the spark plug to run hotter. Never saw any real data on that with before and after temperature reading.
I did many and did them properly. Never had a problem.

 

[RayIN]

DO NOT use a standard cutting tap! Instead use a thread-forming plug tap with an appropriate lubricant. It does not cut, but instead reforms the threads to original. These taps have 4-6 rounded corners instead of being exactly round.

 

[5030]

Not something I've ever had to do because I ALWAYS use never sieze on spark plugs.

 

[JRH02]

DO NOT use a standard cutting tap! Instead use a thread-forming plug tap with an appropriate lubricant. It does not cut, but instead reforms the threads to original. These taps have 4-6 rounded corners instead of being exactly round.


View attachment 3804232

I've always wanted a set of thread forming taps - SAE and metric. Not necessarily for new threads but for chasing.

 

[RayIN]

I've always wanted a set of thread forming taps - SAE and metric. Not necessarily for new threads but for chasing.

There are several designs, be sure to buy a set like the picture. You can feel the "corners" on them. Some have a straight cut in them, which can cut misshapen threads away.

 

[rScotty]

DO NOT use a standard cutting tap! Instead use a thread-forming plug tap with an appropriate lubricant. It does not cut, but instead reforms the threads to original. These taps have 4-6 rounded corners instead of being exactly round.


View attachment 3804232

If you don't happen to have a thread restoring tool in the right size, it is easy to make one in a few minutes by slightly tapering the first few threads of a bolt or spark plug with a hand file, and then using a hacksaw to cut the slots as shown below

I've attached an example of a bolt turned into a thread-restoring tool. And the bolt is still goodto use as a bolt if necessary.

This trick works particularly well for restoring spark plug threads. It's almost a necessary tool in a shop that does work on aluminum heads.

You can control the taper by looking at the top of the starter threads. The one I've pictured is tapered about right. Also, the tool works better if you slightly slant the slots as shown.
rScotty

 

[Cycledude]

I believe NGK plugs come from the factory with a very thin coat of never seize pre applied.

 

[Richard001]

Never put a cold plug into a hot engine. I don't know the science behind this, but it has always worked for me.

Richard