Spark plug thread inserts...

[jdreamer]

Today's "why did I buy a T25?" moment came when I found out that one of my spark plug threads has had an insert installed at some point....and it came out along with the plug It's certainly stuck to the old plug nicely, so little hope of getting it off. So, time for another insert....

...so I've done some searches and come across two solid insert kits (I've used wire helicoils on exhaust studs before, but want to go with solid inserts for the spark plug).

Timesert - look good but don't seem to be many distributors in the UK. I did a quick search on here and they got one minor mention. Anyone used these and/or know where I can get a set?

Draper helicoil - which is actually a solid insert similar to above rather than a wire type, but you make it stick in the tap'd hole by "expanding" the last section of the insert with a "special tool" (lools to me like you bang a tapered bar into the installed insert to force the little lugs out into the head, but I could be wrong). Can get a set for £45 off ebay (or motor factors). Anyone used this set?

I'm hoping that my current oversize thread in the head will accept a new insert without having to cut/tap but that may be wishful thinking (thread seems ok and old plug+insert screws in & out ok). Plugs are M14 and the oversize thread on the old insert (which is now attached to plug as above) is M16 (both 1.25mm pitch). Goind to get a draper insert for £3 (without the rest of the kit) just to check out the sizes, before I go any further.

Any thoughts, suggestions or alternatives appreciated.

Cheers, J

[jdreamer]

anyone?

[syncron ice]

Hi jdreamer,

I posted on this a while ago. Here you go:

I was on a couple of weeks ago re: could I replace cylinder head in situ, I cant find the thread (no pun intended!) so I've re-posted. Anyway, the plug in No.3 blew out and the threads appeared to be ok but the plug could be pushed in and out so I presumed the head was cracked as I'm very careful when replacing plugs. I inspected the head insofar as I could but couldnt see anything. I also noticed a bit of thread stripped off the plug. Worst case scenario was a head replacement so I decided to helicoil it just in case.

This I achieved successfully in situ. I bought a 'sav-a-thread' (M14)by helicoil for $21. This included a 'drill' to make a larger hole, 3 different sized inserts and a metal bar to hammer at the end. (Forgive my lack of knowledge of tool names but I know what they do).

The process:

Clean around existing plug hole. Move any hoses/cables that might impede work.

It is recommended to lubricate 'drill' but from experience I heavily greased it in order to catch all the shards which will collect in the perpendicular grooves. ( Have the piston at TDC which also prevents shards from dropping into the cylinder)

Start the 'drill' by hand (hopefully you will have enough of the old thread) and then onto the ratchet (1/4") with short extension as you start the new cutting.

Patience required, a quarter of a turn at a time making sure to keep the extension bar perpendicular to the direction of hole. Square on in other words. It would be very easy to pull from one side and misalign the 'drill'.

Err on the side of caution and withdraw the 'drill' (slowly) when you think you are nearly there. It will be covered in metal shards thank God so clean it well. Check how far you've drilled and if you see a smaller hole with threads further in you'll have to drill more.

Get a kitchen towel, fold in half, roll into a white cigar! Coat half of it with grease and insert it into the plug hole. Twist anticlockwise and withdraw slowly and voila, more shards.

Coat the 'drill' with grease again; re-insert by hand being extremely careful to be on the right threads and when it tightens put the ratchet back on an finish the bore.

Remove slowly and repeat towel etc. Coat a cotton bud with grease and insert as far as possible and rub around in a slow circular motion. Withdraw slowly. More shards.

Repeat towel and bud a couple more times for safety then the same without grease. Clean around hole also.

Now it time to put in the insert. Check that there's no dirt on the threads and coat with high temp silicone (not supplied, about a fiver from motor factors). Screw a plug into insert to hand tight which then aids fitting onto the right thread and screw in slowly until you come to the non threaded part of the insert. Unscrew plug and use metal bar to gently hammer ( a few taps will do it) the insert fully home.

Wait 24 hours for silicone to set.

Refit cables/hoses if you moved them and fit plug and lead. Do a visual check around engine bay to make sure you haven't left tools/rags etc there. Replace engine cover an fire her up.


JD, its not a helicoil, its an insert made by helicoil and if your inserts threads are ok and you can insert it fully home then maybe using the above mentioned silicone might do it. Good luck.

Hope this is of help.

Tony

[ghost123uk]

Good info for those that need it there Tony
Good enough to go in the wiki ?

My only concern would be how confident are you that no bits of metal end up in the bore ?
Even 1 small bit could spell disaster.

I wonder if anyone has any tips re this aspect of the job ?

Perhaps = Piston at TDC, fill with grease, get grease out after doing job, turn over with plug out and flush with some petrol, don't want a hydraulic lock

[syncrosimon]

Not on a wbx, put in the past I have used a small piece of plastic hosing taped onto the end of a vacuum cleaner, this can then be used to suck up any swarf by popping it through the plug hole. Also have used a bit of thin oil to liquefy around the swarf which helps to suck it up the pipe. May be a good idea to spin the engine over without plug on for a bit to expell any other swarf out the plug hole??

[jdreamer]

Thanks for the replies guys. The "save a thread" sounds exactly like the Draper kit, so good to see some "how to" on this. I've got one of the solid Draper inserts (also made by Helicoil) on it's way to me, as I'd like to see if that will fit in the thread left by my current insert. If so, that'll save me having to drill/tap a large dia thread. We'll see. Off on hols v soon, so doubt I'll get to this beforehand, but I'll post up an update once I'm back.

Cheers, J

[jdreamer]

BTW like the idea of the small pipe connected to a vac to clear swarf. I was thinking about something similar last night, but got stuck on how to get a vac in there - duh!! as you say, there's a bloody great hole where the spark plug is supposed to be

[ghost123uk]

Nothing like resurrecting an old thread

But as it is on the same subject I thought it would be OK ?

So, slight hissing sound on turning over, "I know what that is I thought" = Loose plug.
Don't know why, I fitted them a few thousand miles ago and did them up as I always do, ie "just right" or so I thought.

Went to tighten it up and it became obvious that the thread in the alloy (DG) head was damaged.
Probably by the plug vibrating around loose for god knows how long

So, panic on.

Ring the local garage I trust for T25 repairs.
He reckons no big deal, he has done them before, has the kit and it's booked in on Friday.
I mentioned "how do you deal with the swarfe issue" and he says pretty much as Tony says re swarfe above.

Fingers crossed then, as this engine has been a pearl for the last 2 years since I got it (thanks again billy739).

[ghost123uk]

Just for anyone's future reference, it all went well, my local T25 friendly garage fitted the helicoil with no fuss and at a very reasonable charge.