Stripped Spark Plug

[srcarr52]

When I tightened the plug, the insert came with it.

Darn, now it's time to get it welded shut and retapped. I probably weld up 8 cylinders a year with failed inserts so don't feel too bad.

 

[LondonNeil]

If the thread in the cylinder is ok, put the insert back in and use the right thread lock? Loctite red, permanent lock and seal

 

[srcarr52]

View attachment 92301
I have a timesert kit now after seeing how the save a thread kits are made... they both work though. I would have to order shorter sleeves with my timesert kit. A bit overkill, but it does make her nice and straight. Work is back manageable heading into winter if anyone needs a hand.

That is a nice roll over fixture, what brand is it and how do I get one?

 

[LondonNeil]

Wurth, timesert. The best kit but 'kin costly

 

[twinstaged]

That is a nice roll over fixture, what brand is it and how do I get one?

I will try to see if there is a makers mark on it. I think however is it Shop made and I think I’m the third owner now. Last guy had it set up to do Harley heads. There are cheapie cast iron tilt t slot tables on eBay I have though about grabbing to try though.

 

[twinstaged]

If you weld and retap be sure to use a tap with the proper class for good fit. A lot of taps out there will give you a sloppy fit.

 

[srcarr52]

If you weld and retap be sure to use a tap with the proper class for good fit. A lot of taps out there will give you a sloppy fit.

Yup, I bought a bunch of different taps to find the one I like the best. I settled on a H2 spiral flute tap. The standard spark plugs taps are beyond an H4 fit and very loose when making new threads.

 

[Mattyo]

If the insert came out....you likely didn't bang on it with the mandrel enough. Those teeth have to bite mike....and the jb weld has to be really mixed too...and the insert has to sit just below flush.

 

[twinstaged]

Yup, I bought a bunch of different taps to find the one I like the best. I settled on a H2 spiral flute tap. The standard spark plugs taps are beyond an H4 fit and very loose when making new threads.

Yep sounds good to me. I’ve been happy with these H3 in most materials. Plus hand tapping vs rigid power tap can account for a lot of over cut on such a short distance.

 

[srcarr52]

Yep sounds good to me. I’ve been happy with these H3 in most materials. Plus hand tapping vs rigid power tap can account for a lot of over cut on such a short distance. View attachment 92922View attachment 92923

I find this size and pitch thread to be really sensitive to the drill size. For 14x1.25 12.8mm drill is recommended (.504in) which I think is too large, a 0.490" end mill works best for me.

I power tap it on the mill but feed the quill by hand.

 

[twinstaged]

Minor diameter on a 6h is .498 so I bet that end mill makes her nice and tight. Should get her licked pretty well.

 

[LondonNeil]

What do you do to recut the seat/sealing surface after welding, or do you manage to keep it ok? As Mike knows, and the reason I have been researching inserts, is I have an 038avs that a previous owner helicoiled.... Badly. The insert is firm in place but was too long/not deep enough and when I got the saw it had about half a turn protruding and stopping the plug sealing. I ground off the protruding coil and found the sealing surface beneath mangled over half of the way around. I've managed to get a seal using a 1.5mm copper sealing washer on the plug, and a smear of gasket cement, but still thinking about better solutions.

 

[twinstaged]

What do you do to recut the seat/sealing surface after welding, or do you manage to keep it ok? As Mike knows, and the reason I have been researching inserts, is I have an 038avs that a previous owner helicoiled.... Badly. The insert is firm in place but was too long/not deep enough and when I got the saw it had about half a turn protruding and stopping the plug sealing. I ground off the protruding coil and found the sealing surface beneath mangled over half of the way around. I've managed to get a seal using a 1.5mm copper sealing washer on the plug, and a smear of gasket cement, but still thinking about better solutions.

Any number is cutters in the mill can just touch up that surface. It’s dealers choice there.

 

[LondonNeil]

Thought that may be what you do.

 

[srcarr52]

What do you do to recut the seat/sealing surface after welding, or do you manage to keep it ok? As Mike knows, and the reason I have been researching inserts, is I have an 038avs that a previous owner helicoiled.... Badly. The insert is firm in place but was too long/not deep enough and when I got the saw it had about half a turn protruding and stopping the plug sealing. I ground off the protruding coil and found the sealing surface beneath mangled over half of the way around. I've managed to get a seal using a 1.5mm copper sealing washer on the plug, and a smear of gasket cement, but still thinking about better solutions.

I have to cut the whole sealing face out to be able to weld all the way to the chamber. I cut the sealing surface back down with a large end mill.

 

[srcarr52]

You really have to open them up wide to get the tig torch in deep enough to get good penetration on the chamber side. Plus you have to cut all the threads out to get any contaminates off and start with a smooth surface.

This on had a failed big insert so it was really big and thus easier to weld to the chamber.


The finish weld will be spot faced, drilled and tapped and then faced down to the correct plug height.

 

[Al Smith]

As general info in case you don't know you drop one thread spacing for tap hole size no matter if it's metric or SAE .To get a "round " hole you about need to use a reamer .So that said an M 14 -1.25 would be M 12.75 --12.8 would be close enough .
Most of my metric taps are production taps used in the manufacture of automotive engines .They run a certain number of holes and are automatically changed when that cycle is reached and discarded .They have no measurable wear .The plug tapes I think run a cycle of 8-10 thousand holes and are composite carbine with a hard steel body,CNC style with coolant holes .

 

[twinstaged]

As general info in case you don't know you drop one thread spacing for tap hole size no matter if it's metric or SAE .To get a "round " hole you about need to use a reamer .So that said an M 14 -1.25 would be M 12.75 --12.8 would be close enough .
Most of my metric taps are production taps used in the manufacture of automotive engines .They run a certain number of holes and are automatically changed when that cycle is reached and discarded .They have no measurable wear .The plug tapes I think run a cycle of 8-10 thousand holes and are composite carbine with a hard steel body,CNC style with coolant holes .

Anytime carbide and tap are in the same sentence I see $$$$ lol. Had sticker stock the last specialty solid carbide tap I priced. Makes sense though.

 

[Mattyo]

wait ...what? 8-10k holes?

 

[Al Smith]

Solid carbine cutting aluminum with coolant on a CNC machine .Those numbers are only about one week of production .I don't know what they cost but the reamers which are also carbide are around 200 a pop .
You have remember these are not your fathers Oldsmobile in a matter of speaking .These things are cut to micron tolerances as are most of not all modern engines no matter who makes them .There is no reason other than neglect these things are capable of in excess off 200 thousand miles .I'm old enough to remember doing a valve job at 30 thousand and a rebuild at 50 thou .