Help. I have just replaced my spark plugs, one of the threads inside the cylinder head has become bare and as a result the spark plug wont screw in. Got a new MOT and insurance policy yesterday so the timing couldn't have been worse.

I'm no mechanic but this looks like a new cylinder head or possibly having the thread redone (once the heads out). Anyway ill stop moaning now and get to the point..... anybody have any suggestions where I can get a reconditioned cylinder head from?

I know the Barchetta shares the same engine as other cars so I can widen my search to include other fiat models. I've had a look on e-bay but couldn't see any.

Has anybody else had this problem before and are you able to advise me please?

Barchetta 1996 (The love of my life)

Hi Dan,

I have had a quick search on this forum and found that the engine and mechanicals are indeed shared with the Punto HGT. I'd be tempted to start searching ebay and other sources for the Punto HGT, as your search will probably yield greater results than the Barchetta.

The thread in question is here.

https://www.fiatforum.com/barchetta/170055-new-barchetta-owner-needs-help.html

Best Regards,

JC-T

Hello,

Just to add, I found this information from the following link, which seems to clarify where the engine was also used.

http://www.puntopower.com/hgt.html

[FONT=Helvetica, Arial][SIZE=-1]Fiat Barchetta step1 (the older Barchetta has different ECU)[/SIZE][/FONT]
[FONT=Helvetica, Arial][SIZE=-1]Fiat Barchetta step2 (probably the same ECU)[/SIZE][/FONT]
[FONT=Helvetica, Arial][SIZE=-1]Alfa 156 1.8 16v (the ECU and the engine head is completely different: the Alfa engine has twin spark configuration and more power, 140-144 HP)[/SIZE][/FONT]
[FONT=Helvetica, Arial][SIZE=-1]Fiat Stilo 1.8 16v (the Stilo is given with 3 more HP)[/SIZE][/FONT]
[FONT=Helvetica, Arial][SIZE=-1]Lancia Lybra 1.8 16v (same engine, same ECU)[/SIZE][/FONT]

A comprehensive answer as always...thanks so much

I would also suggest contacting a local auto engineering company, it is possible to drill out the bore and fit a collar that the plug will screw into.

as long as the thread isnt completly stripped, you will be able to repair it easy with a tap.

Had something similar fixed with a heli-coil, I think it only took a few minutes and cost £20 or something, but that was in the early 90s.

Great suggestions....many thanks. I don't want the time and expense of taking the head off, its looking that way though. The thread is bare, I'm concerned that tapping it in situ might be harmful to the engine if anything drops in. I like the idea of a heli-coil, just been looking into it and that might save me a trip to the auto-engineer (thanks Mad Mat) but I still think taking the head off would be wise before doing it.

Am I being too protective?

Once again thanks for the advice people

Hello,

If I potentially carried out the work, I'd be inclined to take the head off, just to be 100% safe. If you're looking at keeping the car long term, which you are, it'd give you the chance to do the job properly.

However, I think I have a tap and die tool that'd be the right size, and with something in the bore to collect the swarf (a small amount of oil or redex for example, it may be do-able. Using an old vacuum cleaner and some hosepipe would then be able to suck out the swarf before it has a chance to get into the Cat.

I like the idea of either a helicoil or drilling out and fitting a collar, as these are more permanent solutions. I have found a link below, containing information about carrying out the fitment of a helicoil. It also gives you time to source a replacement head, but have a running car a the same time.

http://www.popularmechanics.com/automotive/how_to/4212608.html

JC-T

Providing you can get a tap to the plug hole, you don't need to remove the cylinder head to fit a heli-coil. Smother the tap with grease to catch any swarft and withdraw it to clean it off regularly. The hole will need to be taped oversize so the heli-coil brings the thread back to the normal spark plug thread size so it doesn't matter that the thread is bare.

Dave.

JC-T and Dave thanks very much. This is really good news, cheaper and quicker. I wasn't having much joy sourcing a replacement head anyway.

I found a M14 X 1.25 spark plug helicoil thread repair kit that seems to be the type of thing I'm looking for however I cant understand the sizing, does anyone know if this kit would be correct?

I'm afraid I don't know the size. When I had mine done I just phoned around some engineering firms I found in the yellow pages (before this inter-web thingy existed) and they did everything else.

The deal was I'd open the bonnet, remove the engine cover etc. so all he had to do was walk up and do the heli-coil. Kept the price down that way!

If you buy the kit I'd be interested in some photos and a few notes on how you got on

Cheers,

Matt.

I cant find any other heli-coil spark plug repair kits except the one above. Again I'm no mechanic but logically speaking this heli-coil repair kit must be the standard spark plug size for this job? I'm guessing all spark plugs fit into the same size hole in the cylinder head????

Am I making a wild assumption here?

M14 X 1.25 is the most common spark plug thread size and is correct for all the Fiat engines I've ever seen.

There are other size spark plug threads, including M10 and M17, both of which were used on some Ford models and by other manufacturers.

(Can't quite remember what size the old Lodge repairable spark plugs, used back in the early 1900s were)

Dave.

Thanks Dave that's a great help mate.

Swarf will be the least of your problems. Helicoils have a "tang" which is used to wind the coil in with. This tang in most cases, and 100% of the time for spark plugs or any other bolt that extends beyond the lenght/dpeth of the helicol, has to be removed.

The usual/proper way to remove the tang is to 'punch' it of with a short sharp blow. This will result in the tang disappearing inside the cylinder head. Not good news as the helicoil is hardened steel and if not either retrieved or cleanly blown out through the exhaust will most likely jam itself on the perimeter of the crown of the piston and merilly score the bore.

You may be able to remove the tang with some long nose pliers by exerting a rapid and sharp twist. Wrist action will not be fast enough OR sharp enough (due to you hand tissue). You will have to construct/devise a solution that allows you to firmly grasp the tank and then be able to strike a twisting action. e.g. long thin nosed moles grips, solid tommy bar through grip handles followed by swift sharp strike with hammer.

I would create (hand sew) a parachute sock made from light dry linen. This would be the shape of the bore, i.e. round with a matching diameter wall of about 15mm to 20mm wall height, with 4 to 8 strong cotton/nylon shoot strings. Tie the shoot strings together but leave long and of equal length. (Optional - attach a steel washer that could be grabbed by a telescopic magnet). Place into to cylinder bore (retaining shoot strings outside) so it is central and lies over the piston head and neatly tucks up and round the cylinder bores. Place in dry and tease into place. Piston height will be by experiment. Too high and you will have difficult getting to the sides. Experiment, but piston 50% to 75% down the bore is probably the best position for a top entry spark plug hole. When happy drip oil directly onto the centre of the piston/shoot and allow to soak in. Don't get the sidewalls wet! No more than and eggcup full in total. When happy then drop the shoot strings into the cylinder with the knot (with or without was) being placed a central as possible.

Now drill and tap (with grease on bit and tap). Insert helicoil. (Note! check that helicoil is steel and magnetic and not stainless steel before inserting). Try sharp tap twist. Hopefully this will work. If not you will have to be brave and puch the tang off into the cylinder. With luck it will drop straight down or bounce off the cylinder wall into the middle of the shoot. Carefully retrieve shoot by grabbing strings, locate knot and extract shute evenly by gently pulling from knot/washer central point only.

Hopefully you will have a shoot complete with any escaping swarf AND the tang. If not then you will have to go hunting for the tang with a magnet.

Apart from the above all I can say is (a) familiarise yourself with helicoil process (b) walk all steps through (c) look/think of problems and solutions (d) exectute and if any stage goes wrong then (e) DON'T PANIC

Good luck!

Some useful information there. Sounds like someone who's done this before

Well not a helicoil on a spark plug but a helicoil on our Strada Abarth inlet manifold with stripped thread by garage. Sadly I my case, some 19/20 years ago I was faced with stripping the cylinder head, camshaft housing, cam carrier off completely off or doing some detailed research and explority fishing into the inlet manifold holes with bent wire, diagrams etc. etc. Decided that if the tang "went in" then it would lay below the cam carrier or flush down the head and block oil drains into the sump.

The tang did go in and I assume 20 years on it is probably in the sump well away from the oil pump in one of the baffled sump compartments.

All I did, was reason my way through all possibilities, weighed up the risk and went with my findings. In my case I knew that if I did not stop the tang going in then I would have to take the risk or strip down the engine.

With the spark plug at least you know exactly where the tang is and either you create an easy method of catch and extract before/if it goes in or spend a lot longer fish with tools, vacuum/suction pipes, magnets etc. till you retrieve the little bugger.

Mine was the bolts that hold the rocker in place on a Nissan Stanza. When they first went I got a slightly bigger set of bolts from Homebase and used them. I didn't have the cash for anything else and it lasted a year before I found out about helicoils.

Obviously in my case the tang wasn't an issue!

Just to update you all on what happened....

Armed with all the great information I received from this post I called a mobile auto engineer who fitted a thread insert after drilling out the hole. A tiny amount of swarf fell in but she started up fine and is running sweet. Apparently this is a common fault and especially during the summer when enthusiasts service their car and incorrectly fit the spark plug.

I really thought this was going to be both painful and expensive so thanks to you all for the advise.

Time taken - 45 minutes
Cost £96.50 inc VAT

Daniel