Re: Why Not Paint the Heads for Cooler Engine?

["Kenik Hassel" <kenik@telisphere.com>]

After reading your letter I sat down to think about it for a while becaause
painting the heads immediately put up a red flag.  Here is the reasoning I
came up with AGAINST painting your heads.

1)  Sealing-  Any paint between the head and the case would compromise head
sealing since the Type 1-3 case uses no gasket.

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.
	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.

Kenik Hassel

----------
> From: John M. Kowalski <john.kowalski@zg.tel.hr>
> To: Air-Cooled Volkswagen Discussion List <VINTAGVW@SJSUVM1.SJSU.EDU>; T3
Group <type-3@umich.edu>
> Subject: Why Not Paint the Heads for Cooler Engine?
> Date: Thursday, December 25, 1997 1:13 PM
> 
> Volks:
> 
> While painting my new cylinders with flat, heat-resistant black paint
today
> (yes, I know that it is Christmas, but with no family here, it seemed the
> logical thing to do), I started to wonder why no one has stated that it
is
> essential to pain the silver-colored aluminum head fins with flat black
> paint.  In fact, I have not even seen anyone allude to painting the head
> fins flat back to better transfer heat.  Why is this?  Why paint the
> cylinder fins black to radiate heat while leaving the much hotter
cylinder
> heads their natural, shiny silver-colored aluminum?  
> 
> Didn't paint mine yet, but may after I hear your comments.  
> 
> BTW, Tom Wilson suggests painting the cylinder fins flat black to
transfer
> heat better.  
> 
> Thanks much and Happy Holidays,
> 
> John 
> '65 1500s Variant
> '72 VW Cabrio