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MG Midget and Sprite Technical - heli coils

Hi,
I have a little problem with my head - 1275! I had a little water leak from the thermostat cover so over the weekend I checked it out. It turned out to be a stripped thread on one of the studs. No problem, I have several spare studs. But on removal of the stud I discovered the head had been repaired with a heli coil and the insert had come out with the stud. Again, no problem I thought, just screw the coil back into the hole and screw the stud in and away we go, sorted.
The problem is though, I cannot get the insert back in the hole! It will screw in about half way (about 4mm) and that is all. No matter what I do that is as far as I can get it to screw in.
I think the head was warm when I took the stud out. I am going to try to warm the head slightly with a blowtorch to see if that helps and I have also put the insert/coil on the stud with a little threadlock to see if that is any better (The threadlock had not dried and I ran out of time so I will try this tonight).
Anyone got any other suggestions how I get the insert back in? When first fitted, do they just screw in?
Has anyone got a heli coil tap I could borrow to clean the thread (I don't know what size it is)?
Thanks for you help.
Dave
Dave Brown

I have just spoken to Peter Burgess who has explained that you can't get them back in, I need to get a new one. It has been ordered from the good old interweb and should be with me in a few days time. You live and learn!
Dave
Dave Brown

Aye, as you have probably figured out the new coils have a little tang on them that is used to screw them in before being broken off.

Kits are expensive, also considering they only do one thread size but I have a strange love of them, such a smart engineering solution!

Malcolm
Malcolm Le Chevalier

Does he explain why you can't get it back in? I'm very surprised - all it is is non convential sized tapped hole with a sprial wound thread spacer... I imagine if you bought the helicoil kit (and hence the right tap) you could retap the hole to clean it up, cos as you say its prob full of threadlock and rust.

C L Carter

Hi C L,
Apparently, you screw them in with the little 'tang' at the end of the coil. This bit goes in to the newly tapped whole first, so as you screw it in you are making the outside diameter of the coil a little smaller and pulling the leading edge of the coil away from the newly tapped thread very slightly.
Screwing in from the other end would do the opposite - make the coil expand a little and jam in the new thread.

Malcolm,
I think I am getting to like this simple, neat and robust engineering solution too - even though they have left me without my car for a week or so.

Dave
Dave Brown

I've previously used the Time-Sert alternative on a Fiat T/C block for head bolts. This type of repair is superior but probably more expensive.
Derek Stewart

Dave,

Before you go out and buy a kit or get it done it might be worthwhile trying to form a new tang to screw it in with again, you'll lose maybe 1/3 of thread. The bit to be aware of is that the tang also has a notch at the base so it can be broken off once inserted, maybe that can be done with a careful application of a needle file prior to insertion. I think worth a try.
David Billington

Like so.




Lawrence Slater

We have a love hate relationship with serts, they look neater but we have had to work on the threads of spark plug size ones to make them work properly. We paid an awful lot of money for the kit which does look neater than the re-coil/heli-coil ones but not user friendly. They also tend to come out on spark plugs just like heli-coils but easier to thread back in.

Peter
Peter Burgess Tuning

Dave,
I have a number of standard sizes, if I have the correct size that you need, e-mail me with your address I could put one in the post for you 1st class in the morning.(FOC)

Guy
first name AT weller hyphen lakes DOT co DOT uk
Guy W

I hate ti ask the obvious but....

Why not find a fatter bolt in the spare screws jar and just tap the stat hole bigger

Prop
Prop and the Blackhole Midget

I agree Prop. Course it does mean that forever after, you also have to enlargen the hole in the thermostat cover when you replace it. But I reckon that might be better than helicoils and the like.
Lawrence Slater

What happens when the fatter bolt suffers the same fate? An even fatter bolt?!
Malcolm Le Chevalier

prop that is a horrible solution!

1. Its just horrible, I'm shuddering
2. Its means modifiying other parts by drilling larger clearnace holes
3. It looks wrong
4. You are changing stresses and required torque settings - which on more critical components could be disastrous
5. There may not be enough metal to drill you larger clearance holes
6. SHUDDER SHUDDER SHUDDER

C L Carter

I've already done it. Not on the thermo cover/head admittedly, but on one of the radiator captive nuts that I stripped. No problems in so many years I've forgotten how long ago I did it. Works a treat.

I don't think it's that bad a solution, and how often do the thermo threads in the head strip anyway? Once in 40/50 years? It's a thermo cover, not a big end bolt, how much stress is there? 7 or 15 lbs max split 3 ways. :)
Lawrence Slater

I think it the particular application of the thermostat housing, with it being right on top of the engine, the first thing on view when you open the bonnet, it would just look careless to have one oversized stud and nut out of the matched three. Other locations might be acceptable, but not there. A helicoil is such a nice simple engineering solution, it would certainly be my preferred fix for that location.

Dave didn't follow up on my offer - I presume because he has already ordered elsewhere.
Guy W

I've worked with wire inserts such as heli-coils for years. To prevent the insrt from coming out with disassembly, use Loctite threadlocker. for a thermostat housing I would use a high temprature threadlocker such as Loctite 272.

http://www.loctite.co.uk/cps/rde/xchg/henkel_uke/hs.xsl/loctite-4087.htm?iname=Loctite+272&countryCode=uke&BU=industrial&parentredDotUID=productfinder&redDotUID=1000000I9AX
Pete Ottewell

Ah, but there are those amongst us -- I'm in there with my philistinic attitude -- that don't care too much about how the the bolts on our 50 year old engines look, or for that matter some other parts of the car. Just as long as it goes ok. :)

I've used helicoils in the past too, and bloody good they are. But as has been noted, they can also come out. So tapping a larger bolt in place, to me at least, is just as good a solution - even if it can be easily spotted. I'd call it a good bodge. :)
Lawrence Slater

you could perhaps oversized the other two to match :)
Nigel Atkins

Bodge! you said it Lawrence, a swear word to us proper Engineers. Have some pride in your work I say.
Pete Ottewell

For those of us with a lathe or 2 and other tool goodies the possibility exists to tap the hole in the head something like M10, or in this case maybe M12 or 1/2", and then turn a bolt shank down to 5/16" and run a 5/16" UNF die over it at the top so the result would look standard and fix the problem. A possibility but I think I would only do that as a last resort.
David Billington

I can confirm that there is enough metal in the alloy steering rack brackets to drill and tap oversize to 3/8"

Back in the early eighties, my first midget developed a clunk from the front-end. It turned out that one of the threads in the steering rack bracket had stripped. The local BL dealer couldn't get one and, as it was my only car, I opted to fit an oversize bolt to get back on the road.

At the time, I was commuting 30 miles each way, so I couldn't afford to be off the road.
Dave O'Neill2

What are we a concourse site now....i thought we where into modifications....hahaha

Another option would be to do as I suggested above with a larger bolt...then the next time the head comes off....you can weld the hole over and re drill and tap it back to normal.

Personally im not a huge fan of heli coils.. they cost a fortunes and i can never get them to stay in place when removing


Btw... If your worried about IMPORTANT proper torque specs... Im pretty sure i wouldnt use a heli coil...that to me would just be a huge red flag that you can get the proper spec REALLY out of sync fast
Prop and the Blackhole Midget

Prop, That's why i suggested that you should use a thread locker like locktite....
Pete Ottewell

We have repaired heads and blocks by fitting larger size bolts then redrilling/tapping for original thread, especially when someone has made a botch of trying to remove a broken stud!Seems better than throwing the component away?
Helicoils are stronger in ally fitment.

I dont see where the recoils/helicoils cost a fortune? If you were to stock a few sizes you would be able to repair your threads easily not having to go to a machine shop. Most common ones which damage on the A series head are 5/16th UNF and 5/16th UNC, maybe 1/4" UNF for heater take off.

http://www.ebay.co.uk/itm/V-Coil-Thread-Insert-Repair-Kit-5-16-UNC-Compatible-With-Helicoil-/330792512921?pt=UK_Hand_Tools_Equipment&hash=item4d04c52d99

When we 'do' heads we fit helicoils where required free as part of our work. They vary from 40 pence to around £2 (for spark plug size)

Peter
Peter Burgess Tuning

Prop - cast iron welding is a specialist job. You wont do it with your mig.

C L Carter

Hi Peter O. There was a discussion about bodge, a while ago. I can't find the thread, so you'll forgive me for posting the same thing here.

Bodging can refer to a job done of necessity using whatever tools and materials come to hand and which, whilst not necessarily elegant, is nevertheless serviceable. Bodged should not be confused with a "botched" job: a poor, incompetent or shoddy example of work, typically in the field of DIY. A "bodge", is serviceable: a "botched" job isn't.

I only bodge jobs, I never botch them :).

I like P Burgess idea of an over sized bolt, drilled and tapped to provide the original thread. I'm sure I must have done that in the past, as it seems to jog a memory. Getting too old to remember all my "bodges". lol.

Lawrence Slater

That well known firm Bodgit & Scarper eh...
Pete Ottewell

From the on-line Macmillan Dictionary

bodge
- definition


verb [transitive] British informal British English pronunciation: bodge /bɒdʒ/
Word Forms
or bodge up British English pronunciation: bodge up

to do something badly, especially to make or repair something badly because you do not have enough time or the right materials to do it properly

Most of the joinery work had been bodged.
Pete Ottewell

Hey CL carter....

Mig welder ??? Nhaaaa.... I was thinking something even more widely accepted by ozark missourians down south....a tooth pick, or a foil gum wraper, even a Mcdonalds plasic drinking straw works great .... I wouldnt use JB weld tho,thats just to hill billish....hahaha
Prop and the Blackhole Midget

Pete, that's the corruption of the word bodge. Botch is what you are confusing it with.

Here's the origins of the word Bodging as it's known today.

History
The term was once common around the furniture-making town of High Wycombe in Buckinghamshire, England. Bodgers were highly-skilled itinerant wood-turners, who worked in the beech woods of the Chiltern Hills.[2][6] The term and trade also spread to Ireland and Scotland.

Notable bodgers
Samuel Rockall learnt the trade from his uncle, Jimmy Rockall. At the age of 61, Samuel was almost the last of the living chair bodgers.[13] Rockall’s bodging tradition was captured on film shortly after he died in 1962. His two sons helped in the reconstruction of his working life in the woods and his workshop. The colour film was produced by the furniture manufacturer Parker Knoll and follows the complete process using Sam’s own tools and equipment. A film copy is available at the Wycombe Museum.[9]

Another famous contemporary bodger is Dr S. Mcghee, who introduced his trade for charitable reasons to the Xagar in Tibet in the 1990s.[citation needed]

English slang
In contemporary British English slang, bodging can also refer to a job done of necessity using whatever tools and materials come to hand and which, whilst not necessarily elegant, is nevertheless serviceable. Bodged should not be confused with a "botched" job: a poor, incompetent or shoddy example of work, deriving from the mediaeval word "botch" – a bruise or carbuncle, typically in the field of DIY, though often in fashion magazines to describe poorly executed cosmetic surgery. A "bodge", like its cognates kludge and fudge, is serviceable: a "botched" job most certainly is not – but a total failure.

http://en.wikipedia.org/wiki/Bodging

Lawrence Slater

Ah Lawrence, you have trumped me with the reliable source that is Wikipedia it beats those charlatans Macmillan hands down.
Pete Ottewell

If you install Helicoils correctly, they do not come out. The top thread end of the helicoil must be in a full thread - that means more than 3/4 turn below the surface. That is sufficient even for self locking Helicoils, such as are installed as OEM in aircraft etc.

FRM
FR Millmore

Pete; Lawrence,
I would suggest evolving languages or regional variations of use. Both definitions are, or were probably, correct.

I would have used the word bodge as Lawrence describes. And also for chairmaking - specifically the process of turning chair legs on a pole lathe. I believe it is also commonly used as a noun referring to car body filler.

I have only ever associated "botched" with a poorly executed repair. I had thought it was a derivative of butchered, as in hacked about or savagely slain. Parts of my car were definitely savagely slain when I got it
Guy W

Yup you're probably right Guy, and it's interesting to play with words and their origins.

http://www.etymonline.com/index.php?term=botch
http://www.ukcraftfairs.com/guide-to-bodging

Anyway, the point I was really making, is that whatever you might lable it, to repair or remedy something, in a way that doesn't follow or meet with the codes of modern taught professional engineering principles, doesn't make that repair a "botch" for want of a better word. -- Even if an Engineer wouldn't like it :).

If sticking an oversized bolt or stud in, in place of the original size bolt or stud, results in a repair that lasts for 20 or 30 years, I'd call that a sound method of repair.

I might even call it an engineered solution, depending on where you look to find the roots of the word Engineer. Depending on where you look, you get a slightly different meaning.

Etymology
1) The word engineer is derived from the Latin roots ingeniare ("to contrive, devise") and ingenium ("cleverness").

2) It is a myth that engineer originated to describe those who built engines. In fact, the words engine and engineer (as well as ingenious) developed in parallel from the Latin root ingeniosus, meaning "skilled". An engineer is thus a clever, practical, problem solver. The spelling of engineer was later influenced by back-formation from engine. The term later evolved to include all fields where the skills of application of the scientific method are used. In some other languages, such as Arabic, the word for "engineering" also means "geometry". The fields that became what we now call engineering were known as the mechanic arts in the 19th century.

3) The term engineering itself has a much more recent etymology, deriving from the word engineer, which itself dates back to 1325, when an engine'er (literally, one who operates an engine) originally referred to "a constructor of military engines." In this context, now obsolete, an "engine" referred to a military machine, i.e., a mechanical contraption used in war (for example, a catapult). Notable exceptions of the obsolete usage which have survived to the present day are military engineering corps, e.g., the U.S. Army Corps of Engineers. The word "engine" itself is of even older origin, ultimately deriving from the Latin ingenium (c. 1250), meaning "innate quality, especially mental power, hence a clever invention."

4) The etymology of “engineering” and “engineer” derives from “engine” and “ingenious” both of which come from the Latin root in generare, which means “to create”.

So whether you use some kind of threaded insert, or an oversized bolt, or whatever, as long as it's fixed, and importantly, it lasts, does it really matter how it's done?
Lawrence Slater

installing a larger bolt, like painting the engine room and wheel wells black, makes it look like a "slap-dash" repair (cover up what's wrong, rather than correcting it), plus, in the case of a larger fastener, it can not be put right later (the hole is now too large), whereas an insert does allow for that as a last resort later

the uneven / mis-matched fasteners just look sloppy

a heli coil, or time serts, etc. as a repair looks like an engineer corrected it

nothing meant against an engineer who would rather use the larger bolt than an insert, just saying what it tends to look like to others


Norm
Norm Kerr

You wouldn't just enlarge *one* bolt, surely? You'd have to do all 3 otherwise it would look lopsided!

I've just finished putting 6 helicoils in the diff cage of the Mini. The final drive gear is held on with 60 ft.lb of torque, which stripped two of the threads right out of the new (genuine Rover) cast iron cage, but Helicoils handle it without a problem.
Growler

You could just install 10 extra cool looking gauges, and no one would notice the bigger bolt in the thermostate
Prop and the Blackhole Midget

Hi Norman

When someone has made a complete balls up of trying to remove stud and drilled off centre etc etc, would you rather chuck the head away or drill, tap and fit a larger bolt, file flush and then drill and tap to the original. Mostly one cannot see where the larger bolt has been fitted. I wonder if some thread (no pun intended) readers think we mean fit a larger bolt/set screw/stud size rather than use the original stud size located in the larger bolt?

We have spent lots of money on various ways of removing broken studs. When these fail we use stainless steel thread repairs. Final way is to fit a larger bolt and refinish to original size.

What really bugs us is a lot of engineering shops (probably not Stateside where " are still the norm)seem to fit 8 mm helicoils instead of 5/16 UNF/UNC, now that is a crappy repair to us!

Peter
Peter Burgess Tuning

Peter.... Only in branson missouri...lol

Of course we have to remember ... Are we talking studs or bolts...i said bolts because thats what i did on my toyota truck

Ultiamatly it comes down to what is acceptable to the owner, if looks are important then a hilicoil is probably the way, if its a fun beater car to drive, probably just a fatter bolt, me id do the fatter stud and reshape or retap the nut to match the other 2

Heck... Im installing a 3/8 inch spacer between my head and stat housing, so do you think anyone will notice if a stud is a bit bigger

Prop

Prop and the Blackhole Midget

Hi Prop

We do not use a bigger bolt/stud/setscrew to hold the thermostat housing/manifold or whatever. We fit a larger bolt into the original hole. Cut/file/mill the bolt flush with the head. mark out and then drill/tap threads to original size.

Peter
Peter Burgess Tuning

"the uneven / mis-matched fasteners just look sloppy"

Looks aren't everything Norm.

If they were, then bloody great rubbers bumpers would never have been fitted to Spridgets, which a fair proportion of owners seem pretty keen to remove, and spend a fair amount of time and money doing so. :)
Lawrence Slater

I have been in engineering for 34 years, the last 24 working for a well known Aero Engine manufacturer in Derby whose name is famously associated with quality. I think this has had an effect on what I consider to be acceptable and what is just plainly wrong. The use of wire inserts in aerospace is perfectly acceptable and has been tried and tested for many years. The CAA, EASA and the FAA deem the use of wire inserts as an industry standard as indicated by FRM.
Pete Ottewell

In case you hadn't noticed though Pete, Spridgets don't fly (mostly), and don't need air worthiness cert's either. So I reckon there's a little leeway in there to move away from aero parts compliance. Don't you?

I don't think the FAA, the CAA, the EASA, or even the HSE, CIA, or FBI and Mi5/6 will mind, if the MOT doesn't preclude the use of drilled oversized bolt to fix a duff thread. :)
Lawrence Slater

Lawrence, I don't think anyone is trying to say that using a mis-matched bolt is wrong, or less effective, just that it looks sloppy.

Rubber bumpers, and the effort that some folks will exert to remove them, sort of supports my point. Some things just look better than others, and not everyone agrees about it.

Perhaps in the world of cars, looks do count for a great deal. Consider some of the good cars that never were successful, simply because they were awkward, or ugly (Porsche 914, Pontiac Aztek, Ford Ghia convertible).


Norm
Norm Kerr

How about the 11 stud A series head then?

The "front" hole in the 11 stud head, the one just behind the thermostat housing, used only a 5/16" bolt passing into the block - note: bolt, not stud.

Does that diference look sloppy?

It was done of neccessity as far as I know, because of the proximity to the water jacket. But still, at least they could have made a special stud to make it look symetrical with the other studs couldn't they? Or maybe it didn't matter that it didn't match? And I've certainly never seen anyone complain about it being odd.

well, I don't think that a different sized bolt under the bonnet(hood), is really in the same conversation as the overall looks of the car. And anyway, the term 'Frogeye' was an insult at first, not a compliment. It was considered ugly.

Come on fess up. An odd bolt doesn't really matter much, and isn't an engineering gaff at all. IHMO


Lawrence Slater

Thanks peter...i was wondering if that was possiable, to use a bolt and make it flush and redrill and tap the hole...do you use lock tite to secure the flush bolt?

Prop

Prop and the Blackhole Midget

Hi Prop

No need for loctite if you wind it in tight, also the lower threads tapped can be a little tapered if in a blind hole so the mismatch helps hold the bolt tight. No harm in loctite though as it also helps act as a lubricant to increae actual torque. If one goes mad and uses a cast iron bolt the repair hardly shows.

Peter
Peter Burgess Tuning

This thread was discussed between 25/09/2012 and 29/09/2012

MG Midget and Sprite Technical index

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