Damaged Spark Plug Hole Thread Chaser

Life Cars & Motorcycles
141

Don’t do that. The engine gets quite hot, and all that will melt right off after a few miles… Actually the spark plug won’t just melt and come out, it will likely EXPLODE right out of the cylinder during the compression cycle. Not something you want while driving down the highway at 60mph. Oh I forgot to mention solder does not stick to aluminum, in fact not many thing does, even paint. Only thing that sticks to aluminum is eggs when you are trying to cook on an aluminum pot…

Remember the cylinder of an engine is basically a gun… If a spark plug explode out of the cylinder better pray you or your passenger isn’t in its path…

142

No offense but you’re in way over your head at this point if that’s your plan.

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143

None taken. Nuke it from orbit. Its the only way to be sure, right?

I don’t think I’ve suggested at any point that I wasn’t in over my head. If I did, apologies. I didn’t mean it.

144

I’ve seen talk of brazing aluminium with silver solder.

I also saw a fairly astonishing video of some Mongolians repairing a bust aluminium sump by running molten aluminium on it, using concrete as an (outside? not sure. I THINK it was internal and they knocked it out after casting-on the aluminium) mould, and working on the floor of a yurt.

Wish I could find it.

There’s also an “alumaloy” product (I think its a braze) that is supposed to be pretty fried-egg like, but of course I wont be able to get that in Taiwan.

(That prop repair does seem a bit too good to be true)

The thread inserts kits mostly use thread lock, typically Loctite, which, astonishingly, I was once able to find in Taiwan, though the (dodgy?) local “Mystical” brand is a lot easier.

One of the better US thread insert kits uses JB Weld epoxy, and there is a “high temp” putty version of JB weld, though I probably won’t be able to find that in Taiwan.
Re firing right out of the cylinder, could be, but by no means certain, since there is quite a lot of intact thread left.

If it DID explode right out of the cylinder, it’'d take these intact threads with it. Might damage the ignition lead that its tethered by, but other than that, and maybe loosing a spark plug, I’m struggling to see what I would lose that wouldn’t be guaranteed lost by drilling for a thread insert, the “official” solution.

A cylinder is NOT basically a gun. It wont be shooting through the bonnet (hood) and it wont be bringing down any low flying aircraft.

I wont need to pray I aren’t in its path, because I don’t drive around lying on top of the engine. Its too hot, the bonnets in the way, and I cant reach the controls from there.

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145

Hmmm…concrete…but you can’t tap concrete.

Might be able to sort-of-tap (as in form threads in) clay though, running a bolt through it while “green”.

Ceramic plug hole liner…

146

So far (2 goes, one in Tainan, other in Kaohsiung) havn’t been able to get an M14X1.25 bolt.

Weird, but that;s Taiwan

I tried a couple of BIG Bolt Bizniziz, wall to wall Bolt Boxes, bolts from Brunell to Von Braun, a Bolt Bonanza.

Nope.

I tried a few smaller hole-in-the-wall Bolt Boutiques. A couple of them reacted like US rednecks unwillingly confronting the metric system for the first time, but that was probably just a reaction to my foreigness.

One guy spent quite a while digging out some M14X2.0. No idea why.

I mean, I might not have known a couple of weeks ago what the 1.25 meant (though I might have guessed) but his Business is Bolts.

Bolts are his Business

Bolts, in fact, are his Bread and Butter (with a side-dish/sideline/garnish of Nuts), and Id shown him a spark plug, but he still looked surprised 'when I pointed out the much coarser thread.

Still, nice of him to bother looking.

This simply cannot be unobtanium, even here, but I got hot and pissed off and gave up.

I’ll try again later.

Or maybe there are some on the car??

147

Get a long wheel stud.

And give it lot’s of ugga duggas.

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148

I still have no clue why you can’t just run a thread chaser tap thru the hole far enough to restore the whole thread and be done with it. I speak from experience. There shouldn’t be any interference because the spark plug couldn’t be installed if there were anything impeding the tap from going far enough to restore the complete thread.

149

OK, recap on some clues.

I’m coming from behind (Oo-er Mrs), from inside the head. so normal spark plug installation is irrelevent.

The head is contoured and has valves to provide obstructions. These obstructed the non-tap thread chaser I used earlier, but actually I THINK it got deep enough to work if it was going to.

I’m coming from behind so I can use the undamaged threads like a jig, to address my skills defecit. Unlike you, I can’t speak from experience, but perhaps your procedure could work, though I dont have a thread chaser tap.

My failure to get a thread chaser tap MIGHT have been because I only had a picture of it, without the correct Chiwanese/Japlish translation (tap is “tappu”, apparently), but I don’t think so, because they tried to sell me the non-tap spark plug chaser I already bought from them, so I suspect they didn’t have a chaser tap.

Tap purchase attempt at the Kaoshiung Good Tool Shop was a bit of a screwup (NPI).

They showed me a box with three, which they said were a set, with different tapers. 650 the set or 290 for one.
OK I’ll get the set, (though I couldn’t offhand see the difference) then realised I was 150 short.

Left box on the counter, asked them where the nearest ATM was, said I’d be back, with gestures and pisays

On return, they’d sold one of them.

ÖK a set no more , “which one do I need?” ses I

“They are both the same” ses they.

Pissed off once again, so I went somewhere else.

These were thread cutting taps. Not the same thing. They were also quite short. Tried a few places to get a longer one, but allegedly special order.

It may run through OK, but I doubt it’ll redirect the new hole the spark plug has already cut. The non tap spark plug chaser certainly didn’t

150

As @QuaSaShao said, pictures would be very helpful. Describing it is hard enough, and there’s a million variations depending on the exact model of the car/engine.

A machine shop would be able to provide a good repair. To helicoil them you have to first drill it out, then retap it with the thread for the outside of the helicoil. This isn’t something you should do yourself especially if the thing’s as contoured as you say.

But I seen spark plugs and never seen them with a long thread… so again, pictures would be extremely helpful.

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If you want to get all fancy, get one of these or these but, seeing as you have the head off already, just get one of these or a long wheel stud or a length of threaded bar and ugga dugga it from the rear. You’d be done by now.

152

Well knock me dahn wiv a fevva!

You found a back tap (entirely unknown to tool shops in Tainan and Kaohsiung, and apparently suspected to be whatever the Chiwanese is for “Flying in’t Face O’Nature, and a Work Of’t DEVIL” if it did in fact exist, in some foreign place.

If I’d known about that when I had the head on, I’d have bought it.

Indications are, however, that it wouldn’t have worked.

I got a (single) tap yesterday. 300NT. Dunno what taper it is. Havn’t tried it yet.

Couldn’t get a bolt.

I’m really tired of Taiwanese tool shops.

Wouldn’t M14 be a bit compact and bijou for a wheel stud?

(I think the M stands for MEIO)

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See helpful (No, really, apart of course from the timing. Might still help someone else) post above. Thats what a cylinder head looks like.

The problem is in cylinder 3. The two round things are valves. Fortunately (because I hadn’t thought of it before I took the head off) both valves are up in the head, so in minimum obstruction mode.

The shoulder on the right of the chamber has an angled hole in it which is where the spark plug should emerge. The shoulder conacts the hex drive on the non-tap spark plug hole chaser and is gouged by it.

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M14x1.25 is not a nonstandard tap. Every cutter shop should have it.

You need to go to a shop that sells cutting tools, NOT “hardware stores”!!

Like this

They sell end mills, lathe tools, etc.

They’ll have taps of nearly all sizes.

155

I have an M14X1.25 tap, as described above, tho maybe TLDR applies.

I just don’t have a forming tap. This may be because I couldnt specify it in whatever the appropriate language might be.

I suppose I should have tried improvising some Japlish. “Formu Tappu”, "Chassee Tappu "?

I couldnt get an M14X1.25 BOLT. That’s just weird, but its Taiwan.

Thanks for the link. Could be a useful resource in the future, if there is a future.

156

Form taps are called 挤牙丝攻

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157

Thanks. Looks like one of those (RHS) is tapered, the other (LHS, bling finish) straight.

Which would be the best choice here, or doesn’t it matter?

I’'m thinking tapered if coming from the damaged outside, and it doesn’t matter coming from the undamaged inside, so tapered would be the more versatile choice?

158

What length/style M14xP1.25 bolt do you need?

159

Tapered tap is for starting holes, and the non tapered is so you can tap to the bottom of a blind hole. It doesn’t matter for your use.

I’m suggesting a form tap because it does not cut, it forms a thread by squeezing the metal into the shape of the thread. So there’s no chance of screwing up existing threads.

160

Style? er… Hex bolt, though I suppose a square bolt would be OK.

Continuously threaded (i.e. no plain shank) probably best here.

Not a carriage bolt, U-bolt, hangar bolt, bolt of lightening, cloth, etc, etc…

Length er…long enough. say 10 cms to be safe. 8 would do.