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Hissing cylinder head!


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Hello Everyone,

 

Well just as the sunshine appeared I noticed a hissing and bubbling of water from the head gasket at the front of the engine near the water pump on my TR4A

So, it looks like I'll have to take the head off and have a look

Whilst I'm at it I thought I would get the head converted to unleaded

a) Can anyone recommend a specialist I could take the head to for this work and roughly how much it will cost?

(I live near Buckingham so somewhere close would be good but I'm happy to travel)

B) As it's a long time since I took the head of my Mk1V Spitfire, are there any pitfalls to be looking out for?

eg if the heads reluctant to part company, are there any modern day solvents to use to help break the seal rather than brute force?

Any other jobs worthwhile doing whilst the heads off? (Guess if there's a water leak somewhere, there could be a blockage?

 

Thank you for any help/advice you can give me

 

Regards, Nick

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Hi Nick ~

Your cylinder head should lift off easily. Don't forget NOT to turn the engine with the head off otherwise

you'll unseat the wet liners. If you decide to remove carbon from the piston crowns then leave a ring of carbon

on the outer diameter as this forms a sort of oil control.

Tom.

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Hi Nick,

the headgasket doesn't normally pop where there is only the coolant holes. You may find some serious corrosion on the head/block interface.

Why not check the head bolt torque before you go too far. If the leaky area torques down further then you mat have solved it.

 

Solvents are not good as they can't get to the sealant (if there is any) as it is all clamped together.

I used a hydraulic engine hoist to lift a stuck head once.

 

as mentioned with the head off do not rotate the crank unless the liners are clamped down.

 

Roger

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Getting worse!

 

I decided to follow Roger's advice and torque down the head bolt near the leaky area

 

I applied some effort, not a lot, and the nut started to move.....brilliant I thought, should be able to tighten it up

 

However, soon realised the whole stud was turning so the thread must have stripped

 

Can't believe it, the car's been running great for years

 

I guess this means there could be some bad corrosion lurking around the stud area

 

Can't see any other option now but to take the head off and I guess think about whether it can be "hellicoiled"

 

Feeling frustrated and checking my bank statement !!!

 

Any ideas greatly received

 

Nick

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Hi Nick,

firstly - do not panic. Secondly - PANIC!!!!!

 

You need to take the head off to see what is happening.

There are two types of stud location -

one has the threads in the hole near the surface (easy to see and fix)

The second has the threads set at the bottom of a hole (difficult to see and not so easy to fix.

As well as a stripped thread it could also be a sheared stud - if the hissing/bubbling started suddenly(ish) then it sounds more like a sheared stud

 

Report back on what you find for the next installment.

 

Roger

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We had a topic recently where we had to help fix a broken long stud with a botched Helicoil.

Who's car was that?

 

During this I found out at the normal 110ft lbs torque value is too close to the limit for cast-iron.

 

Keep posting on here because there is a lot of experience with fixing damaged head studs.

I've done several including removing them when broken off below the surface.

 

I've got Helicoils for this BTW.

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Hi Alan

 

That's reassuring news....seems there's always someone somewhere who has experienced everything to do with TRs!

My panic has subsided a little as the stud in question is one of the shorter ones according to the manual

However, I 've started to put penetrating oil on the various nuts and bolts to be removed and on saturday I'll will begin!

I'll feel even less panicking if the nuts holding the exhaust downpipe free up easily as i've had problems with these in the past

I'm hoping that when I lift the head the situation wont be too serious so , my glass is half full at this stage!!

Thank you for the offer of the Helicoils....that's great

Will keep you updated

Regards, Nick

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Hi Nick,

keep the glass half FULL. (an optomist = 1/2 full, A pessimist - 1/2 empty, An engineer = glass twice as big as required)

 

If you find that the stud has broken then ensure that when you drill into it the hole is as central as possible. Make a jig to guide the drill.

For a near surface sheared stud a plate bolted to the other studs will help. If it is a deep threaded stud then life is easier as close fitting rod (old stud) with a hole down the centre works well (go out and buy that lathe you always wanted).

Somehow you will need to remove the thread that is left behind but can be done.

 

If the thread in the block is sheared off then heli-coiling is the option and works well - possibly stronger than the original thread.

You will find that the helicoils will not be long enough, but you can stack them on top of each other to increase their length.

 

Paul in Canada did this last year.

 

Roger

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Just to re-iterate:

 

1. a grade 8 steel, high grade for aerospace or marine, UNC bolt recommended torque is about 140 ftlb

 

2. this is if its dry, you take off 30% if its lubed

 

3. cast-iron is NOTHING LIKE a grade 8 steel bolt

 

4. 110 ftlb is, I believe, TOO MUCH really especially now this material is old.

 

Now I'd say that a head bolt is very likely to have oil in the hole even if not actually lubricated when assembled.

 

This is important to understand. We are measuring the tightening-torque as an INDIRECT way to get the right TENSION

in the bolt.

 

If the bolt is lubed we will get the tension long before we develop the "right" torque.

By the time the torque rises to the "right" value we will pull out the thread.

 

The figures for the UNF end of the thread are higher so you won't tend to strip the nuts.

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Hi Alan,

I have a couple of queries -

 

Is the block cast Iron or a cast Steel. It doesn't drill like cast iron but I don;t know for sure.

 

The stud UNC is not torque loaded into the block so it can be put in wet (a smear of copperease) but run down by hand or double nut and nipped.

The UNF thread at the top end does not need lubricating but again a light smear of copperease may prove useful.

The 105ft/lbs applied at the top end will be reflected at the bottom end as well. So, the WSM says to use 105ft/lbs where is the problem - also consider most amateur

torque wrenches are not spot on.

 

If you under torque you run the risk of popping the HG. But there is the small risk of stripping the block thread at the stated torque is fitted dry.

I would suggest using the light smear of copperease and the stated torque load. This may be a little under torque.

 

Roger

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You may be right. Perhaps it is cast-steel.

This would make it like a Grade 2 bolt I should think. Does it drill easily?

 

I can't get an HSS drill into a high-spec bolt.

 

The fact remains guys quite often pull these threads out. Why does this happen?

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It is not so much the torque that matters but the axial load it transmits. For that the thread type (fine or coarse), length and engagement should be as long as possible to distribute the loading and prevent over stressing.

 

As for the torque necessary for a 1/2 unified thread my Machinery Handbook indicates that 105-110 ft lbs for a Grade 2 steel is OK but the limit is approaching.

 

Tim

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Roger,

 

The original torque settings are quoted dry, if you fit " a little copper slip" onto the UNF thread on the top nut it will reduce the resistance of the nut on stud fit, hence a 105lb ft torque indicated will actually have increased the stressing on the stud, effectively having increased the the torque applied to the stud.

To ensure this does not occur read what I have answered to AlanT below.

 

AlanT,

 

"The fact remains guys quite often pull these threads out, why does this happen ? " because Alan these "guys" don't do the ground work first.

Before fitting any stud to the engine I soak them in a pot of best thinners and then clean the threads with a clean lint free rag and chase down the threads with a fine point scriber. Any rough areas are found by the scriber point and I then inspect the threads minutely to see what causes the problem. Often it is an ingrained swarf piece from a prior badly fitted stud, these pick out with the scriber, sometimes it is the residue of previous fitting gasket "goo" Wellseal or the like, often the thinners will remove this and then the scriber finishes the task. Sometimes the rough spot is a scuffed or "dragged" thread form either like it from new or the result of a stud being badly fitted previously, if these threads cannot be cleaned up by gentle fileing with a needle file to regain the thread profile or "lose" the drag marks on the thread wall then the stud is discarded and another good one substituted.

The threads in the block are not cleaned with any fluid due to the difficulty of ensuring the thread is cleaned and dried completely, just blown clean with compressed air and again the threads inspected to ensure the best possible thread form. Any stiff or dragging threads have a tap gently chased down them to help reshape or clean the thread.

As regards to fit with thread lubrication or not I only use the lubrication stated by specialist bolt suppliers ie ARP for their products if used. For TRs the stud threads only have a wash in WD40 and are then gently wiped with a dry lint free rag, any residue left on the threads should be minor and that helps provide a smooth fit to the fastener components. The studs are screwed into the block by hand and should run up tight to the shoulder and limit of the threads, any sticking or reluctance to do this remove that stud and check again the thread forms in the block (only possible on the short studs obviously) and also that stud. Swap the stud with another and see if the problem persists, if it doesn't discard that problem stud and fit with another better stud. Continue to fettle any studs until they all fit by hand and they feel...good.

Does it surprise you to know that stud fitting alone can take between 1 and 2 hours ? however it does pay dividends, I haven't stripped or sheared a stud or thread used in a standard manner on any of over 20 of these 4 cylinder engines.

 

 

 

Mick Richards

Edited by Motorsport Mickey
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Mickey, I was really hoping you would post this advice again.

 

I am trying to make readers grasp the difference between the torque wrench reading and the force shearing the thread out.

 

I am pretty sure that these get threads get wound out of the blocks because the holes in the block get filled with oil and the effect on the torque required is not realised.

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Regarding torque, I've found that checking my Torque wrenches and individual torque settings on my Acratorque meter (£30 from Anchor supplies (ex MOD sell off purchaser) about 30 years ago gives excellent results.

 

The Acratorque is self calibrated and cannot go out of "set" unless you set fire to it or drive over it! It's range is 0-500 lb ft and it's especially useful when we use it with one set Battlefield wrenches (fully plastic enclosed ex WD torque wrenches) these have to be set by Allen key against the Acratorque at one specific torque setting, ie wheel torque or whatever. This then takes the pressure off a poor squaddy trying to change an engine or whatever under battlefield conditions under muck and bullets! Works for me.

 

Doesn't help if the stud hole has swarf or oil or other contaminants at the bottom of it though, and is a good reminder of what has to be done to obtain top reliability from not only this but any engine. Make no mistake this 4 cylinder engine design is a beauty to work on, robust, with incredible expansion of power and torque available to over 100 % of the original design parameters! you just need to give it the basic minimum engineering care it needs and it will pay back in spades.

 

Mick Richards

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Guys, interesting debate going on here although I need to revisit some real basics

 

Reading Roger Williams book and removing the head......he talks about soaking the studs with penetrating oil for a week etc and then removing the complete stud

 

Is that the way to go or should I be aiming to undo the nuts and attempt to lift the head with the studs in place?

 

Nick

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Im no expert but I have removed the head three times in the last three days!

 

Removeing the studs first may make lifting the head off easier but I can really see how it can be done unless the studs can be screwed out by hand

 

There is not enough thread showing above the head to lock 2 nuts onto the stud and I would not want to do that anyway as it will certainly damage the thread.

 

The head should come off with the studs in place with a bit of jiggling.

 

Make sure you have a firm grip on the head (no oily hands) and you have a clear route to your work bench - you dont want it to slip out out of your hand en route.

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Just take the nuts off and pull straight up.

 

You may have to get a stud out first if there is a lot or corrosion around it and you can't slide up.

 

The double-nut method is common practise and won't hurt the thread unless you over do it.

Railways used this to lock rails in place for years.

 

Get some "half-nuts" if the thread is too short.

If you have stripped a stud there will need to be a lot of wiggling about to get it free.

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Nick,

 

Normally when I undo a "Titanic" relic engine with lots of corrosion on it I first wire brush all the stud threads showing through the nuts (normally only a small amount) and then apply WD/Plusgas etc your choice of penetrant.

 

I don't normally have to wait and set about undoing the nuts, (obviously a flat drive socket and substantial breaker bar). In 70% of cases I've managed to get all the nuts off and without damage to the threads, any obstinate nuts I apply heat and then let cool rebrush the the threads and apply more favourite penetrant and repeat the process, often a short stud will come out with it's nut which is fine. That normally sorts out all but the most committed of stuck or stubborn studs/nuts, if there is still a nut that won't budge I will apply the double nut method and see if the stud and nut can be removed together. Of course it's likely that any studs which are corroded are likely the longer units, if the head can be wiggled up the studs and removed then more applications of penetrant in a little reservoir of plasticine around the stud for a couple of days will sort it or if especially bad try diesel.

 

By a variety of these methods all studs and nuts will remove and if you have the misfortune to break a stud then that also can be removed...but that's another story.

 

Mick Richards

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