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Re: Why Not Paint the Heads for Cooler Engine?

I am not sure of the answer but I do know that I would have to disagree with
you anwer....

>1)  Sealing-  Any paint between the head and the case would compromise head
>sealing since the Type 1-3 case uses no gasket.
this would not be an issue if you would not paint the combustion chamber or
the Cylinder sealing surface,  however you would also want to mask off the
spark plug location, and the entire rocker box( including valve cover gasket
sealing surface.

>2)  Heat transfer-  This is the important one.  First think about what the
>purpose of the fins on the heads are.  Dissipating heat.  What is the tin
>for?  Absorbing that heat quickly away from those heads.  Now, the fins are
>painted flat black because flat black is the finish that best absorbs
>visible light, ultraviolet and infrared heat since seeing black is a result
>of full absorption of the radiation spectrum.  This is good. This allows
>the tins to absorb a good amount of heat away from your heads.
               in his message he is talking about painting the actual
cylinders flat black.....which I have also read helps in heat TRANSFER (this
being the ability to give away, as well as recieve heat)

>	Now why paint the heads black?  On top of adding a layer of insulation to
>the heads (i.e.  Thick black paint), you are giving the heads the ability
>to reabsorb the heat they gave off in the first place.  In the close
>quarters beween the heads and the tin, this is pretty easy to do.  The
>heads absorb heat directly from the combustion source, so removing, not
>adding,  heat quickly is paramount.  Ideally, all of the heat given off
>from the combustion process would be passed out through the exhaust gasses.
> Unfortunately, this does not happen.

>	Your goal is to let the heads RELEASE heat not absorb it.  If it were a
>perfect world, all air cooled cylinder heads would be polished to mirror
>shine so the exterior could reflect as much heat as possible.  Painting
>your heads is just plain bad news.  If you already did it, take your
>beautiful new black heads and soak them in laquer thinner over night. 
>You'll thank me.
flat black is proven to increase heat transfer --- that is why brack drums
if ever painted should only be painted flat black it helps them in
transfering heat to the surounding air.... if this theory was not true
everyone would be going aroung with mirror polished brake drums ( a mirrored
surface will actually cause the surface to retain heat, which is not what
you want your cylinder heads to do)  I have never seen ANY air cooled
cylinder head polished to a mirror shine, in any aplication, and I doubt I
ever will, this would cause the cylinder head temperatures to skyrocket .
If your theory about mirrored surfaces were true ( black just absorbing
heat, and mirrored surface releasing  heat) wouldn't the bottom fuselage of
the space shuttle be mirrored for reentry into the atmosphere, which in that
application it must withstand temperatures much greater than we will see
with our air cooled heads 

Todd Daley               
Ontario, Canada
'80 Rabbit Convertible 
'71 Type 3 Squareback    

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