Helicoil or replacement rear head?

[Fozzie]

Hi everyone,

Had to revalve the front cylinder after a cam chain slippage last week. All fixed but as I was putting one of the 14mm bolts in to fix the head down the socket split in two and one bit ended up in the oil pan. So not wanting to leave it I went to remove the oil pan but when trying to remove the rear exhuast, one of the studs into the rear cylinder sheared off.

Anyway i've tried grips, heat, using a vice, squaring it a little for better grip, everything I can find online but it won't budge. As far as I can see i've got two options left. Second hand rear cylinder head or drill and helicoil.

Ive seen a rear cylinder for about £60 and helicoil kits for about £30 and money is getting tight. If I go down the helicoil route, it will be with a saw or grinder to make the stud flush, punch and drill with a standard power drill. Has anyone used a helicoil for this before? Or should I just go straight for the second hand head? Last thing I want to do is buy the helicoil, screw it up and have to buy a second hand head anyway.

Any advice would be magic....

[Zakalwe]

Have you tried welding a nut onto the stud? The heat will usually free the stud.

[Fozzie]

I dont have access to a welder. Buying one would cost too much and the garages ive called wont touch it for fear of cracking the head I guess...

[tony.mon]

If the stud's poking out enough to grip it in a vice, and it still won't budge, try drilling down the centre.

If you drill in line with the existing one you'll not wander off line too much.
Them, while t's still hot, use a broken stud extractor.
Biggest one you can get, as the smaller ones break real easy....

Otherwise, try just drilling the stud out oversize, then fitting a bolt into the hole once you've tapped it.
I can't remember for sure, but I think a 5/16" whit is the first usable oversize, and a bolt of the right length will tighten just before it hits the bottom of the hole you've drilled and tapped.
And it goes through the hole in the clamp without opening it out.

Advantage of this method is that you won't have a broken stud with a snapped easy-out in it.....
Although the head's made of alloy, and isn't designed to have a bolt in and out of it very often, it'll last ok if you don't keep pulling the exhausts off to clean them.

[Fozzie]

Hmmm previous experience with stud extractors means I dont trust them so drilling oversize sounds like the best bet. After flattening the edges of the stud off im gonna have to make it almost flush with the head before I can drill it. How deep do I need to drill?

[tony.mon]

If you drill a smallish pilot hole down the middle you can feel when you've drilled through the end of the stud, because it doesn't go right to the bottom of the hole.

[marlbororman]

tbh i really would of tried welding onto the end first and removing it that way, vauxhall heads, on cars, are common for studs snapping all the time on manifolds, and that is the sure fire way , my mate gets all them out, 100%, and the heads are really soft alloy on them. think on one, he even had to grind the alloy away slightly around the end of the stud to get on it, coz it was that short, and slightly inside. but still came out. Same with spark plugs on fiesta`s, they always shear off flush too.

[Zakalwe]

tbh i really would of tried welding onto the end first and removing it that way, vauxhall heads, on cars, are common for studs snapping all the time on manifolds, and that is the sure fire way , my mate gets all them out, 100%, and the heads are really soft alloy on them. think on one, he even had to grind the alloy away slightly around the end of the stud to get on it, coz it was that short, and slightly inside. but still came out. Same with spark plugs on fiesta`s, they always shear off flush too.

^^This^^

You have to get the stud properly hot (I mean dull red hot), in order to break the bond with the head. You will only get it this hot with an oxy-acetylene torch (a MAPP torch MIGHT work), or by welding a nut onto it. The advantage of welding the nut on is that it also gives you something to grip on to.

I would try this.....drilling it out would be my last resort as the potential for wombles it up is much higher.

Have a look here. The guy is a bit sanctimonious, but he speaketh the truth

[benny hedges]

i usually find a good twatting with a dot punch does the trick.
very often ive tried everything and managed to shock them loose with the corner of a snapped drillbit - getting it hot will help if it's had loctite in or galvanic corrosion has set in.
even worth using a dremel to cut a slot in the head then get the impact driver & a flathead on it.
means you can fix it in situ rather than have to take the head off for what might only be a 5 minute job.
stud extractors are a waste of time imo, 9/10 you will break the extractor & good luck finding a bit that can get through that

[Fozzie]

Thanks for all the input. After much effort drilling and blunting drill bits left right and centre my wife decided just to buy me a replacement cylinder head so she spend time with me! Very nice of her!

Anyway I've now got 3 stud nuts and need a 4th. What internal size do they have? I can't seem to find a nut that matches...

[benny hedges]

is it a front head??? if it is i'll buy it off you so you can recoup some of the cost
just to build a refurb just in case

[Rider on a Storm]

is it a front head??? if it is i'll buy it off you so you can recoup some of the cost
just to build a refurb just in case

I no its a bit late but, centre punch it and if you no the size which i recon is m8 stud, drill it with a m6 then increase by .5 at a time, as you get near the original thread it just falls away, you can actually feel through the drill when this happens, more often than not you will not even have to re-thread

[Fozzie]

is it a front head??? if it is i'll buy it off you so you can recoup some of the cost
just to build a refurb just in case

Na sorry its the rear.

I no its a bit late but, centre punch it and if you no the size which i recon is m8 stud, drill it with a m6 then increase by .5 at a time, as you get near the original thread it just falls away, you can actually feel through the drill when this happens, more often than not you will not even have to re-thread

Thanks for the advice, i'll give it a go when I have some time as I have got my hands on a second hand rear head. If I can drill it out I'll sell it on.