Extra thick head gasket for Mondeo Ecoboost?
Discussion
227bhp said:
HustleRussell said:
Wouldn't fancy trying that on an Ally block
Why not?What if the head was bolted down to a steel bed that had a flat heat resistant material on it to stop the heat transfer?
I'm more than curious now and apologise if the OP feels i am hijacking this topic
I have a head to remove in the near future and it may need skimming or straightening and skimming
"Please Mr Mignon spill the beans"
I'm more than curious now and apologise if the OP feels i am hijacking this topic
I have a head to remove in the near future and it may need skimming or straightening and skimming
"Please Mr Mignon spill the beans"
HustleRussell said:
227bhp said:
HustleRussell said:
Wouldn't fancy trying that on an Ally block
Why not?You'd have to be really careful how much heat you put into the head though, too much and it could ruin it for good because I think, but not sure that heads are heat treated from the factory. Whenever i've had any welded the process is:
Heat area to be welded or entire head to a safe, but not too hot temp to help the weld otherwise you spend too much time trying to get heat into the head via the Tig and it doesn't work very well.
After the repair is done grind it down roughly immediately, but leave it high. Get out the engineers hammer and peen the f
k out of it as it cools, this compresses and hardens the new work before finally finishing it off to the correct dimensions.Mignon said:
Think about it. What causes a head to warp? I'm not talking about just the obvious but at a molecular level what is a "warp" in a piece of metal? In which fields of metalwork do we encounter such things, what is done about it and what is the technical term for that?
30 years ago when faced with a really badly warped head (20 thou or so) I worked all this out from first principles and then rather than machine the head true I straightened it first and then skimmed the last thou or two off to get a perfect gasket surface. It has been an invaluable thought exercise in redeeming heads that might otherwise have been past using again.
My guess:30 years ago when faced with a really badly warped head (20 thou or so) I worked all this out from first principles and then rather than machine the head true I straightened it first and then skimmed the last thou or two off to get a perfect gasket surface. It has been an invaluable thought exercise in redeeming heads that might otherwise have been past using again.
- Strip the head of all combustible materials
- Put the head in a pre-heated kitchen oven whilst the wife isn't looking - Gas mark 7/ 220 degrees C (conventional)/ Refer to manufacturer's instructions for fan assisted models.
- Leave the head in the oven until you're confident its heated through uniformly
- Using suitable PPE (Kevlar oven glove?), remove head from oven, sneak out of kitchen with same and immediately place onto cylinder block mounting face (prepared earlier)
- Install head bolts/ nuts/ studs as applicable and torque up
- Leave to cool naturally
- Remove head once cool and measure residual distortion
HRCM is close, a few unnecessary bits.
A warp is an indication of stress locked into the component. The head overheats on the block but is constrained by the head bolts. The stress gets trapped in the metal. This is encountered in all casting and forging processes so before machining takes place such components need to be stress relieved. If this is not done the stresses might come out after machining and lead to components out of spec. That consists of heating to a medium temperature, well below melting point but sufficient for the molecules to rearrange themselves into a stress free orientation.
So clean the head up, strip it of all removeable components. Give the little woman some pocket money and tell her to f**k off and get a hairdo or summat and pop it in her nice clean oven at 200C. Leave for 2 hours. Switch off and let it cool slowly in the oven. Remove when cool and bazinga, head is now magically straight again. I've straightened heads with 0.5 mm warp that you could have just bolted back onto an engine but a light skim always makes sure.
A warp is an indication of stress locked into the component. The head overheats on the block but is constrained by the head bolts. The stress gets trapped in the metal. This is encountered in all casting and forging processes so before machining takes place such components need to be stress relieved. If this is not done the stresses might come out after machining and lead to components out of spec. That consists of heating to a medium temperature, well below melting point but sufficient for the molecules to rearrange themselves into a stress free orientation.
So clean the head up, strip it of all removeable components. Give the little woman some pocket money and tell her to f**k off and get a hairdo or summat and pop it in her nice clean oven at 200C. Leave for 2 hours. Switch off and let it cool slowly in the oven. Remove when cool and bazinga, head is now magically straight again. I've straightened heads with 0.5 mm warp that you could have just bolted back onto an engine but a light skim always makes sure.
Mignon said:
HRCM is close, a few unnecessary bits.
A warp is an indication of stress locked into the component. The head overheats on the block but is constrained by the head bolts. The stress gets trapped in the metal. This is encountered in all casting and forging processes so before machining takes place such components need to be stress relieved. If this is not done the stresses might come out after machining and lead to components out of spec. That consists of heating to a medium temperature, well below melting point but sufficient for the molecules to rearrange themselves into a stress free orientation.
So clean the head up, strip it of all removeable components. Give the little woman some pocket money and tell her to f**k off and get a hairdo or summat and pop it in her nice clean oven at 200C. Leave for 2 hours. Switch off and let it cool slowly in the oven. Remove when cool and bazinga, head is now magically straight again. I've straightened heads with 0.5 mm warp that you could have just bolted back onto an engine but a light skim always makes sure.
Can I do this with a Peugeot 1.9 XUD Diesel head or is there something else that needs doing?A warp is an indication of stress locked into the component. The head overheats on the block but is constrained by the head bolts. The stress gets trapped in the metal. This is encountered in all casting and forging processes so before machining takes place such components need to be stress relieved. If this is not done the stresses might come out after machining and lead to components out of spec. That consists of heating to a medium temperature, well below melting point but sufficient for the molecules to rearrange themselves into a stress free orientation.
So clean the head up, strip it of all removeable components. Give the little woman some pocket money and tell her to f**k off and get a hairdo or summat and pop it in her nice clean oven at 200C. Leave for 2 hours. Switch off and let it cool slowly in the oven. Remove when cool and bazinga, head is now magically straight again. I've straightened heads with 0.5 mm warp that you could have just bolted back onto an engine but a light skim always makes sure.
PS you DON'T ever remove stresses from anything by clamping them down to something. The stress just acts as an internal spring. You can bend something straight but it'll spring back again. Even worse if you take the head out of the oven hot and bolt it to a block it'll cool while it's in a stressed (clamped) orientation and you'll lock those stresses back into it. Stress comes out with heat as the molecules rearrange and it locks back into the unstressed condition as it cools slowly. Cooling quickly is how you harden metal which in effect is locking stresses in while the molecules are semi molten and in a hard crystal arrangement. Cool slowly and it all takes place by itself. No further intervention needed.
Mignon said:
Penelope Stopit said:
Ok no worries I'll scrap the head. Thanks
Well if you ask a f**king stupid question.....I'm renowned for being knowledgable, not patient!
Anyway I have now searched elsewhere for information and have learnt that the job is nothing like as straight forward as what it seems to be
Having read the following of which I include a link to the original PDF file I am now doubting that it is worth me or anyone taking the warp out of a cylinder head by heating it up in the oven unless they are able to measure the hardness of the cylinder head before and after the process
There is too much work involved in removing, repairing and refitting a cylinder head if there are any unknowns about the end result
Below is a copy of what I have learnt about heating cylinder heads to remove warp
_________________________________________________________________________________________________________
ACL TECH TALK
Straightening Aluminium Cylinder Heads
Care should be taken when straightening
aluminium cylinder heads. The manufacturers of these components
recommend against the practice because of the residual stresses generated and the risk of softening.
However,
aluminium cylinder heads are expensive to replace and as a result numerous straightening
techniques have been developed and are in use in the reconditioning industry.
The following comments are intended to point out that a straightened
ylinder head may never be as good as
a new one and that the risk of problems developing later, particularly in relation to gasket sealing, are greater.
The process of straightening involves the application of heat, whether in an oven or by flame, and under no
circumstances should the temperature be high enough to cause annealing (
ie. permanent softening) of the
aluminium alloy.
The
aluminium alloys used in cylinder heads will anneal at 662 F (350
°
C), but considerable softening begins
at around 554-590 F (290-310
°
C)
depending on the alloy and the time that the head is held at that
temperature.
When using temperature sensitive crayons, excessive temperatures may be experienced due to the delay in
the response of the crayon, or to uneven heating of the head. It is recommended that cylinder heads
are not
heated beyond 482 F (250
°
C)
when straightening.
If annealing has occurred in an
aluminium cylinder head, the material strength is reduced and it becomes
more ductile. There could be some permanent thickness change in the areas underneath the head studs or
some penetration of the washer into the softened and more ductile head material. This effect will be
increased when the engine heats up due to the greater expansion of the
aluminium head compared to the
steel studs.
Any thickness
change which occurs in a softened
aluminium
cylinder head will reduce the clamping pressure
on the gasket. The achievement of correct clamping pressure on the gasket is critical to its performance and
any loss could lead to a lack of sealing and failure of the gasket. At this point, it is no use being critical of the
gasket, it is the condition of the
aluminium cylinder head which caused the failure.
The
behaviour of
aluminium cylinder heads in an overheating situation will differ, however in either case
overheating (whether on the engine or when straightening) will reduce hardness and strength. As a guide,
any used
aluminium head which has hardness lower than 65
Brinell is likely to have been permanently
softened by overheating.
Cylinder heads are made in a variety of
aluminium alloys and may be either gravity or
low pressure die cast.
The heat treatment applied to the casting varies according to the alloy used and results required. It is not
possible to
generalise on the hardness achieved in manufacture. For example, some
aluminium heads are
solution heat treated and aged to a hardness of 110-120
Brinell, while others are
stabilised only (
ie. oven
aged) as the removable core is burnt out and these have a hardness of around 80-90
Brinell.
The above implies that anyone straightening an
aluminium cylinder head should have equipment for
measuring hardness.
______________________________________________________________________________________________________
http://www.acl.co.nz/wp-content/uploads/19-Straigh...
Mignon said:
kerplunk said:
Mignon> It's academic now but I'm curious how much straightening a badly warped cylinder head would cost ball park
Nil. Ball park. Could run you as high as 10p for electric.kerplunk said:
and who does it?
You do.Penelope Stopit said:
as you know the peugeot XUD 1.9 Diesel cylinder head is made of Aluminium
Of course it's aluminium as is the OP's. Cast iron heads don't warp so the issue doesn't even apply to them! Well they might just if you got them to about 900c but the car would be on fire and the cylinder head would be the least of your worries.Penelope Stopit said:
Anyway I have now searched elsewhere for information and have learnt that the job is nothing like as straight forward as what it seems to be
Snip more stuff you've trawled from the internet and got in a tizzy over.Yes it is. It's as simple as baking pies. That's why it's done at 200c, way below the temp at which aluminium alloy anneals or any conceiveable hardness issue can arise. If the head is already too soft (never happens except with crappy Rover K series heads) you wouldn't know about that anyway and machining it straight wouldn't help you either.
Edited by Mignon on Thursday 11th October 16:17
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