Date: Sun, 19 Jul 1998 00:35:56 EDT
Reply-To: CarlMarin@AOL.COM
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: CarlMarin@AOL.COM
Subject: Flat Black Engines
Content-type: text/plain; charset=US-ASCII
Somebody wrote in part:
<<<<<<
Gary;
This MAY (or not) have been a bad idea. I know of at least one air cooled
VW engine that suffered from overheating which also had it's block
painted. We theorized the paint acts as a heat barrier preventing the oil
from cooling properly. Ask around, you might be OK since your oil has an
intercooler. I figure better safe than sorry.
Drive Safely & Good Luck
Ken Lewis<Kernersville,NC>
On Sat, 18 Jul 1998 20:35:18 -0700 Gary Kovach <dearbo@EROLS.COM> writes:
..... I painted the engine flat black,
>Gary
>88GL - Baltimore
>
<<<<<<
Some things to think about. There are three types of heat transfer:
Conduction, Convection and Radiation. Generally all three are happening in
the back end of the Vanagon. What?? Radiation in the back of my Vanagon???
Holy Stuff Batman!!! Seriously, when it comes to cooling from the case of
the engine, most of whats going on in the engine compartment off of the block
itself is convection, heat being picked up from the swirling air back there.
Flat black will increase radiation heat transfer but smarter people than me
seem to have figured out in the past that in most common applications the
increase in heat transfer from the flat black gets cancelled out by the
insulation effect that comes from the coat of paint. Lesson is to have the
block clean and make the coat of flat black very thin, just the lightest
fogged on coat is best. Even then, the flat black isn't doing too much more
than the matte natural aluminum color of the block. Polished aluminum blocks
would be very bad however. Don't do this! Anyway, if doing the flat black
trip, you must have a radiation receiver of course which is everything else in
the engine compartment that the block "sees." So one would need to also paint
the sheet metal in the engine bay flat black as well to get the most bang from
the flat black Krylon. If the engine compartment is very warm, as in the car
sitting in traffic with little air flow, the sheet metal of the body around
the engine very warm, there ceases to be much of a temperature gradient and
there ceases to be much in the way of radiation heat transfer as well. So
worst case cooling scenarios are those in which you are relying most on
convection and radiation effects are secondary anyway.
If you fly your Vanagon at high altitude, up over 70,000 feet where convection
falls off due to thin atmosphere, then once again, radiation would take over
and dominate. Flat black would be the way to go.
How did that sound? Like a reason not to bother with flat black engines?
regards,
Carl
84 and 85 Westies with caked on greasy grime covering both engines. If I
remove it will they leak?
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