Spark plug hole thread chaser.

trianglelaguna
I'll take several deep breaths before attempting this one. Thanks!

daveo wrote: 650ed

I'm using NGK BR8EIX platinum plugs that have washers, but they are pretty well flattened-out from repeated tightening.
The book calls for 20 ft. lbs. torque for the plugs...so that they be.

It looks like those plugs have the same reach (length) as standard plugs, so that shouldn't be an issue, but maybe new washers would keep them up just a tiny bit which might help a little. Can you see any carbon deposits in the first couple threads? Ed

Yes, they will have identical reach and length. Never replaced just the washers, but never ran 50k plugs in an engine where I pulled and checked them every 2-3k miles. Although I did run two strokes for a decade or so until they quit making them, where I pulled and cleaned them every 1k miles or so.

650ed

New washers? Where can I find some of those?

The initial threads may be damaged or cross-threaded (often resulting from some earlier ham-fisted plug installation) making it impossible to get a plug properly started into the hole.

Often, there's a lot of good undamaged thread remaining deeper inside the hole past the shallower cross-threaded area.

The challenge then becomes how to perfectly re-thread the shallow cross-threads to sync perfectly with the deeper good section.

It may be possible to re-cut the cross-threads by starting at the deep end with a reverse tap, also known as a back tap.

The reverse tap inserts all the way through the spark plug hole, and then the tool's deep end expands to begin tracking along the good threads from the deep end, and re-cuts the cross-threaded section as the tool proceeds upward and out of the hole.

It's akin to having the head off, and re-threading the hole in the normal manner starting with the good threads on the piston side of the plug hole.
A reverse tap accomplishes the same result, but without needing to remove the head.

Here's a pic of the reverse threading tool.



Good Fortune!

I am a poor man money wise and when I need to chase a thread where I don't have the correct tap like a spark plug I take my cut off wheel in my die grinder and cut a slot down the length of the threads.

Then I just wire brush the plug to get any excess residue from the grinding. We were taught this in a mechanic class. Works to clean out funky threads.

Also it sounds like your pulling your spark plugs to often. I am sure you could run a tap down just make sure your at tdc. Most taps are angled on the end slightly. So you will need to run the tap down into the top of the chamber a little bit. So make sure the valves are out of the way. Also be sure to keep the tap greased to catch as much as possible. But you also gotta think of it this way. Metal and aluminum expand and contract and diffent rates and temps. Also your putting metal in aluminum, so it will oxidize together over time. I would be sure to use a little bit of antisieze.

daveo wrote: 650ed

New washers? Where can I find some of those?

Well, silly me! I have often read that when re-installing spark plugs new crush washers should be used. Trying to find them is really tough! It is easy to find "indexing" washers, but they are not the same. They are flat washers used to adjust or "index" which direction the spark plugs ground electrode points inside the cylinder. However, I did manage to find one place that says they sell 14mm crush washers by the small bag:

www.gsparkplug.com/shop/spark-plugs/spar...rs-14mm-10-pack.html

Ive heard of people indexing the plugs. How many people and has done it? Is it worth doing? It dosent sound real hard just getting them pointing in the right direction might be a tad tricky but shouldnt be to hard.

Click > All NGK Spark Plugs are manufactured with a special trivalent Zinc-chromate shell plating that is designed to prevent both corrosion and seizure to the cylinder head; Thus eliminating the need for any thread compounds or lubricants.

Good Fortune!

good info patton thanks.

Well, I did it! Just went for it on the cooled down engine.
I was a bit nervous about doing this with the head mounted, but it didn't really matter much. TDC 1&4, then 2&3...done.
Had the shop-vac set up with a piece of vinyl tubing, and greased up the chaser. There wasn't much metal shaved off the threads, but there was some. The vacuum suggestion worked great too.
Thank you all...

Beer for everyone! :whistle:
Maybe the next round.