Helicoiled spark plug hole

At the moment I've put that plug back in but the question is how do I remove

I'd not mess about trying to retrieve a helicoil from an old plug. Have a new helicoil fitted. (How much are they btw?) DaveK.

New helicoil. The end of the helicoil is supposed to dig in & stop it coming undone, presumably the old one was a tad too long.

coming undone, presumably the old one was a tad too long.

Google search brings up quite a lot on Helicoil. Cheap, but I suppose the spark plug hole has to be drilled out accurately and the swarf removed which puts the cost up. Definite no-no to put sealant on the thread of the fitting going into the Helicoil,-in fact they recommend Molybdenum Disulphide or similar lubricant to prevent it seizing. Suppose Coppaslip would be ok. DaveK.

Well you can do it that way. But on an old car you bring the piston up to just below TDC, pack a lot of grease in the hole & then run the helicoil tap in. The stripped hole is ~the right size (sort of by definition). Then snip helicoil to right length & insert in hole. Bring piston to TDC & the grease expels the swarf for you.

They're not exactly cheap if you have to buy the special tap, fitting tool and possibly a very odd sized drill, although the coils themselves aren't too bad.

If you grease the drill and tap and work slowly, you should be ok for swarf, and a small amount of aluminium swarf shouldn't hurt anyway. What you do have to be careful of on some heads is fouling the valve seat insert.

I'd use some anti-seize compound on plugs into an ally head anyway.

clean out of the

the plug hole

today and when

with it.

how do I remove

locktite the

helicoil from it

That should never occur with a properly fitted 'Helicoil'. I'de suggest you take it back to whoever fitted it, an get them to fit one properly. And if they told you it was a Helicoil, make sure they fit a Helicoil, not one of the lesser quality makes like 'Recoil' etc. IME only Armstrong 'Helicoil' inserts are worth fitting. I've tried Recoil and other makes. They are nowhere near as good as Helicoil, They're the only make that I've never had any problems with. One reason I'm sure, is that it's almost impossible to fit a Helicoil without the proper insertion tool, that closes the insert down in dia. All the other makes merely need a slotted rod and a little pressure to start them off. I'de suggest that either it wasn't a 'Helicoil', or the plug had been replaced with loctite or similar, and the Helicoil insert was stuck to it. Mike.

clean out of the

to the plug hole

today and when

out with it.

how do I remove

locktite the

helicoil from it

stop it coming undone, presumably the old one was a tad too long.

Nope. It's retained by it's own spring pressure, and the fact that any attempt to unscrew, unless done from the top coil only, just tightens it. Like a spring clutch that only permits rotation in one direction. Mike.

Try it, if you leave the end sticking out some of them come out again. Definitely works better if you cut them to length.

Loctites pretty pointless at those temperatures anyway IMHO. However, fair point, whoever fitted it out to fix it.

wrote.

fact

only,

out again. Definitely works better if you cut them to length.

Spark plug Helicoils should already be the correct length. Cutting shouldn't be necessary. Unless done very carefully, by grinding rather than snipping, there is a danger of damaging the lead of the thread insert, which can result in shaving the thread of the screw or plug fitted. I must have fitted hundreds of Helicoils in my job as an engineer. Many different sizes. I've never known a correctly fitted Helicoil to come out. IMO the OP's Helicoil? just hadn't been fitted properly. Mike.

IIRC, it should *always* be shorter than the thread it's replacing - says so in the instructions.

Should be , but not all holes are the same depth , In this case I'd suspect it wasn't tapped all the way to the bottom. I get to helicoil a lot of "thin" alloy plates & cutting them to length makes a vast improvement in their retention.

The problem with greasing anything fitted to your cylinder head is that the grease will turn to carbon on the threads and stop the threads from unscrewing nicely. It's kind of a no win situation, but a very thin smear is probably best.

-- James

point, whoever fitted it out to fix it.

Thank you all for the replies. The car is booked in tomorrow (friday) to have a new helicoil fitted, hopefully it will be fitted properly this time!

BTW, my news server has gone down so I'm having to resort to using google groups instead.

Thanks again.

-- Michael Cotton

Rub a pencil (soft is preferable) along the thread or put a little copper grease on it.

That is supposed to ease the release when you next remove it.

But wouldn't the lead knacker your catalytic convertor?

You forgot the smiley :-) There.

Casting bread on water...