Spraying head gaskets.
Discussion
I know not to believe everything in print,so want to sound this one out. I'm reading through one book on engine building and it mentions that unless the manufacturers instructions explicitly say not to, you should spray headgaskets in aluminiumised paint both sides prior to fitting. Has any one any views on this and the logic behing it.
Regards
Iain
Regards
Iain
It will also depend on the block/ head and gasket materials. If using a composite gasket then the fibres allow for any block imperfections. If using a metal gasket then corrosion could be an issue hence the spray? I've never sprayed a gasket and can't say I know anybody who does.
Boosted.
Boosted.
Personally I can see the merit in using *some sort* of lubricant in this situation. Certainly in a fibrous gasket, I can see it helping to prevent the gasket sticking to the machined face of the head.
This would have advantages not just from the perspective of reusing the gasket. Who would reuse a fibrous gasket? I think, more from the perspective of removing the residual gasket from the interface if bits of it stuck.
From my own experience, it's quite difficult to get rid of the stuck bits, without remachining, or alternatively scratching or maybe affecting the flatness of the mating faces. Re-machinig can mean that you affect the CR, and are then into using specialist gaskets, but TBH the scratches shouldn't be that much of a problem until the head has been removed a few times, where they tend to attract stuck bits, and the problem worsens.
I really don't know about Aluminised paint. That sounds sticky, and it's the opposite of what you might be trying to achieve. Anything like this is always going to mean very careful choice of products. Probably the only way to find out exactly is to ask the guy who had the idea, and see exactly what product was in mind.
At a guess, I'd say that a graphite based substance would be better, if that's what is being attempted. It cant burn, it's quite slippery, and fairly dissimilar to all of the other materials likely to be involved.
This would have advantages not just from the perspective of reusing the gasket. Who would reuse a fibrous gasket? I think, more from the perspective of removing the residual gasket from the interface if bits of it stuck.
From my own experience, it's quite difficult to get rid of the stuck bits, without remachining, or alternatively scratching or maybe affecting the flatness of the mating faces. Re-machinig can mean that you affect the CR, and are then into using specialist gaskets, but TBH the scratches shouldn't be that much of a problem until the head has been removed a few times, where they tend to attract stuck bits, and the problem worsens.
I really don't know about Aluminised paint. That sounds sticky, and it's the opposite of what you might be trying to achieve. Anything like this is always going to mean very careful choice of products. Probably the only way to find out exactly is to ask the guy who had the idea, and see exactly what product was in mind.
At a guess, I'd say that a graphite based substance would be better, if that's what is being attempted. It cant burn, it's quite slippery, and fairly dissimilar to all of the other materials likely to be involved.
Edited by dilbert on Friday 30th November 03:43
Thanks for the replies folks, didn't expect quite a debate about it!! For reference the book in question is http://www.amazon.co.uk/Engine-Builders-Handbook-T... and the author is talking about new gaskets.
Regards
Iain
Regards
Iain
stevieturbo said:
The spray the yanks use, is to help seal. Not lubricate.
They commonly use "copper spray"
I think its basically a high temp, non-setting gasket type compound.
Yep that sounds like the sort of thing I was thinking. I wasnt suggesting lubrication, per-se, more "non stick".......They commonly use "copper spray"
I think its basically a high temp, non-setting gasket type compound.
Which leads me to the thought of perhaps using some sort of teflon compound?
Edited to add, if there is no aluminium involved (iron and steel), the best solution must be to use a copper gasket which ought to need virtually no sealant, but being dissimilar metals, copper and ally aren't a good choice at an interface. Ally with iron or steel should be OK.
The trouble comes with an ally head or cylinder, where a fibre gasket is good, but potentially problematic in a "stick" sense!
Edited by dilbert on Friday 30th November 17:23
Dilbert said
"
Edited to add, if there is no aluminium involved (iron and steel), the best solution must be to use a copper gasket which ought to need virtually no sealant, but being dissimilar metals, copper and ally aren't a good choice at an interface. Ally with iron or steel should be OK".
Copper won't seal all that well unless the block surface is near perfect hence the reason for composite gaskets. Even mls won't work unless the head/block surfaces are really flat. I've had problems with one mls type engine and reverted back to the composite offerring which did seal the waterways under pressure. The problem was down to the finish of the head.
"
Edited to add, if there is no aluminium involved (iron and steel), the best solution must be to use a copper gasket which ought to need virtually no sealant, but being dissimilar metals, copper and ally aren't a good choice at an interface. Ally with iron or steel should be OK".
Copper won't seal all that well unless the block surface is near perfect hence the reason for composite gaskets. Even mls won't work unless the head/block surfaces are really flat. I've had problems with one mls type engine and reverted back to the composite offerring which did seal the waterways under pressure. The problem was down to the finish of the head.
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