Cross threaded spark plug

[kevtherev]

PTFE tape round the thread ? Got to be worth a go while you save up for a helicoil ?

Ian

Yeah, I did think that Ian, but thought it might melt. But if it's good enough for my sump plug then ...

Also though about a bead of high temp gasket sealant around the seating edge of the washer. Might try both.

I take it then that helicoils are damned expensive. Or is it the labour to have it done?

Both are expensive
In the end you're going to have to do it.. you might put it off for a short time, but inevitably it will not last.

[itchyfeet]

I think spark plug is M14x1.25mm Helicoil kits are not so expensive on ebay from £11 with drill and tap and tool, probably poor quality so maybe pick a better one to budget.

Never done a spark plug but I did my sump plug and it's not too hard.

you can grease the drill and tap to catch most of the swarf but I guess straight access to drill the hole is the problem with spark plugs.

[kevtherev]

Never done a spark plug.

You only get one chance at this, so mis information could be costly.
Personally I would buy the best and get somebody to take the responsibility of fitting it with a guarantee in case of failure.

[jamesandtheopenroad]

Personally I would buy the best and get somebody to take the responsibility of fitting it with a guarantee in case of failure.

How would you go about doing that? Would it need to be a standard garage or a precision engineer? And what happens if they fubar it?

[itchyfeet]

Never done a spark plug.

mis information could be costly.

where's the mis information?

[kevtherev]

A time-sert would be better as there's no drilling and the coil wont come out when the plug is removed the next time it has to be changed.

[kevtherev]

here's a video of the whole thing with a cutaway engine

http://www.youtube.com/watch?v=Ntiy8L97Nco

[ghost123uk]

My local tame T25 friendly Garage did exactly this on our Tin=Tops engine a couple of years ago. They were very "Yeh, don't worry, piece of pizz for us" = I was not so confident, but £50 later = job done and no problems since (including more than one"spark plug out and back in" scenario).

Fingers crossed you have it as easy as that

[jamesandtheopenroad]

Thanks for all your suggestions. I will try the temporary fix and start hunting around for a garage who can, ideally (from looking at the video) time-sert, if not helicoil, a new thread.

I'll keep you updated.

[sarran1955]

Hello,

This is a cut and paste from an old reply..

Depending on how much access you can make for yourself, and hoping that there is still some thread metal left in the spark plug hole.....

The proper way to do this is to helicoil it with genuine helicoils. I have the tooling for this, and would do it by post, or you can get an engineering shop locally....don't forget that once you have gone this far you might as well get both heads off, 4 helicoils, fit new valve guides, exhaust valves, and valve stem oil seals. Bits are not dear, but there is a fair bit of work.

Now for the 'get you out of the sh*t solution.

Take an old spark plug of the right length and remove the electrode. Now cut vertically down with a hacksaw or a 1.6 mm stainless cutting disc, offset to avoid the central electrode, two thirds of the way down through the thread. Blow clean with compressed air, and make sure there are no loose bits of ceramic. The idea is to rethread this plug into the damaged hole with a '2 steps forward 1 step back, movement. If you have fine valve grinding paste put some on the cut plug thread , this will help.

Wind the plug out, clean the thread with thinners on a cotton bud, blow everything clean with compressed air.

Now try the new plug. It would be a good idea to know how many turns needed to lock the thread. If the plug nips up ok, then wind it back out, use a smear of copperslip grease and Hey Presto.

A straight bit of rubber tube/hose over the end of the plug can be helpful to get it started in the thread.

If the plug still feels rocky, then use Bearing locking compound. I use BERNER HBL 60, in a little yellow bottle. Clean everything with acetone, apply product, and put plug straight in. This product WILL destroy what's left of your thread when you take the plug out, so now you know how long you've got before dropping the heads.

Fingers crossed...

Cordialement,

[Ian Hulley]

fit new valve guides, and valve stem oil seals.

On a WBXer ?

[jamesandtheopenroad]

Was thinking about it in the bus.

As far as I can tell, it's only really the centre of the thread that's gone. If you were very careful and greased the male thread of the spark plug, could you put a little JB Weld on the affected female thread of the engine and using the greased male thread, gradually create a new groove?

That's probably an awful idea, right?

[Fin]

you can grease the drill and tap to catch most of the swarf but I guess straight access to drill the hole is the problem with spark plugs.

You could always turn the van upside down

[Ian Hulley]

Was thinking about it in the bus.

As far as I can tell, it's only really the centre of the thread that's gone. If you were very careful and greased the male thread of the spark plug, could you put a little JB Weld on the affected female thread of the engine and using the greased male thread, gradually create a new groove?

That's probably an awful idea, right?

Let's just embrace the concept of a helicoil shall we

Ian

[kevtherev]

Time sert requires less surgery.
If the thread is in tact then re tapping with the special time sert tap will be more accurate
And permenant IMHO