Buggered plug threads

[Woodslasher]

My 461 started running a little funny while I was test running it so I shut 'er down and when I poked at it I noticed the plug seemed a little loose, but when I pulled the plug I noticed the threads looked a little buggered. The plug still threads in fine and I feel like I can get it plenty tight, do y'all think I should worry about it?

 

[davidwyby]

I’d say run it

but would like to see more of the threads before engraving that in stone

 

[davidwyby]

Worse comes to worse, there are steel thread inserts...3/4” fine thread...hi temp hi strength loctite. I had a go round with them on my 2166

 

[drf256]

Run it but be careful when you snug the plug up. The 461 are notorious for stripping plug threads. Some type of manufacturing flaw to them.

 

[srcarr52]

Run it but be careful when you snug the plug up. The 461 are notorious for stripping plug threads. Some type of manufacturing flaw to them.

It's a low grade alloy and doesn't weld clean or easy. I've fixed 4-5 of those cylinders now.

 

[davidwyby]

It's a low grade alloy and doesn't weld clean or easy. I've fixed 4-5 of those cylinders now.

Sounds like more raisins for a steel insert.

Video: 2166 low power, stalling. Diagnosis? | Page 2 | Outdoor Power Equipment Forum (opeforum.com)

@Woodslasher I never got around to pinning mine, but the loctite is holding. Steel insert in aluminum is standard upgrade procedure in machine shops...

 

[srcarr52]

Sounds like more raisins for a steel insert.

Video: 2166 low power, stalling. Diagnosis? | Page 2 | Outdoor Power Equipment Forum (opeforum.com)

@Woodslasher I never got around to pinning mine, but the loctite is holding. Steel insert in aluminum is standard upgrade procedure in machine shops...

I said they didn't weld easy, doesn't mean I can't weld them. When done the threads are stronger and have a better fit than OEM.

 

[davidwyby]

I said they didn't weld easy, doesn't mean I can't weld them. When done the threads are stronger and have a better fit than OEM.

Oh, yes, I know, wasn't implying that. Maybe have to weld, grind, weld a couple times to get the crud out. Good point on the new material being better than new.

 

[davidwyby]

@Woodslasher I'd clean it real good and put anti-seize on the threads.

 

[heimannm]

I have used the Heli-Coil kit on several spark plug repairs and they all held up very well. These are not the more conventional spring type Heli Coil inserts but a solid insert that is swaged to hold it in place.

Amazon.com: Helicoil 5334-14 Save-A-Thread Thread Repair Kit M14 x 1.25: Automotive

Mark

 

[davidwyby]

I tried one of those in my above thread and it came loose. Maybe I didn’t get it swaged properly, but I think it was lack of thread engagement.

 

[drf256]

I have used the Heli-Coil kit on several spark plug repairs and they all held up very well. These are not the more conventional spring type Heli Coil inserts but a solid insert that is swaged to hold it in place.

Amazon.com: Helicoil 5334-14 Save-A-Thread Thread Repair Kit M14 x 1.25: Automotive

Mark

I’ve used the same Mark. They do work well.

Welding and repairing is far from easy. Makes one’s skills shine through, like Shaun’s do.

I pretty much made a mess of them trying to weld. You need to keep everything (drill/face cutter/tap) at exactly the same axis when you finish as well. And welding in a hole and getting it even is rough. I think Shaun uses a bunch of tricks to do that. He one talented guy for sure.

 

[av8or3]

My fave is plain old helicoils. Every single hole that is tapped on an aircraft engine has a Heli-coil in it. From the spark plug holes down to the 8-32 screws used to hold baffling. It’s a little scary doing the first couple, especially if the part is made of unobtanium, but the results will speak for themselves. Also, always use an anti-seize compound on steel spark plug threads that are screwed into an alloy cylinder head or any other fastener that has to be removed periodically.Even after it’s been helicoiled .

 

[srcarr52]

I’ve used the same Mark. They do work well.

Welding and repairing is far from easy. Makes one’s skills shine through, like Shaun’s do.

I pretty much made a mess of them trying to weld. You need to keep everything (drill/face cutter/tap) at exactly the same axis when you finish as well. And welding in a hole and getting it even is rough. I think Shaun uses a bunch of tricks to do that. He one talented guy for sure.

Thanks for the compliments.

I've invested some time and money into tooling/fixturing to make my life easier. Bolting the cylinder to a plate to drill/tap is much more stable than trying to clamp it in a vise and a floating tap holder is a must for the large diameter fine thread when power tapping. Just a few of the tricks, not all of them.



Welding is a pain and so is finishing the chamber by hand. I've been temped to make some sort of chamber reamer.

 

[davidwyby]

Noice! That is a bit of work there.

For the chamber, maybe a ball mill and CNC program?

 

[BuckthornBonnie]

Thanks for the compliments.

I've invested some time and money into tooling/fixturing to make my life easier. Bolting the cylinder to a plate to drill/tap is much more stable than trying to clamp it in a vise and a floating tap holder is a must for the large diameter fine thread when power tapping. Just a few of the tricks, not all of them.

View attachment 298515 View attachment 298514

Welding is a pain and so is finishing the chamber by hand. I've been temped to make some sort of chamber reamer.

View attachment 298516 View attachment 298517 View attachment 298518

You’ve done two for me and I wouldn’t hesitate to get ya lined up again. Nice pics!

 

[srcarr52]

Noice! That is a bit of work there.

For the chamber, maybe a ball mill and CNC program?

That would take a long time to setup and program for each chamber, I'd rather just have a hand reamer to get it close and then blend by hand.

 

[drf256]

Still using 4xl cups to get down in there, or just filling jug with Ar and super long stickout to blend in the bead from the plug hole?

 

[srcarr52]

Still using 4xl cups to get down in there, or just filling jug with Ar and super long stickout to blend in the bead from the plug hole?

I use the super long gas lens or cup to reach the chamber. The big key is getting enough filler in from the outside so you just have to blend the edges a bit from inside the cylinder. I also have learned to roll up a thicker aluminum or a tin slip to protect the cylinder wall.

 

[Woodslasher]

I was puttering around in the shop and decided to revisit the 461, but when I pulled the plug the threads looked fine and the plug felt solid when I screwed it back in. Apparently it "fixed" itself, (or the plug threads cleaned up the cylinder threads) so for the time being I'm not gonna worry about it.