I know this has been covered to death, but...

[Corwin]

I've read probably 15 threads about painting an engine case and I'd say half say it's okay, half say it's not a good idea. So there's definitely not a consensus.

That said, if there IS decreased heat dissipation caused by painting an engine case (not the cylinders, just the case), how serious are we talking here? A few degrees? Could this potential effect be mitigated by using a 1.5qt. oil sump and 8-pass oil cooler? I realize we're in the hypothetical realm here and no one can really say for sure either way, but I'm looking for a professional perspective.

I'll admit it - I want to paint it for looks to match my car. And yes, my car is a show car, but it does get driven around town too. Por-15 makes a pretty nice engine painting kit in a color pretty damn close to my car's color. Engine I am building is a 1914cc with a brand new AS41 case, tapped for full flow and lots of other goodies. I wasn't initally plannning on the upgraded oil cooler or sump but I can easily add that.

So what do you guys think?

[Bashr52]

A thin coat of High temp black BBQ grill paint on the cylinders and even the heads have been shown to reduce engine temps by as much as 20 degrees. I painted the block in both my 72 and 69 and they both run cool. The 72 has the stock cooler set up, my 69 has a remote cooler and oil sump.

[krusher]

I would say the temp difference would be very small, if the right paint.coating was used the case could actually shed more head than if it were bare.

[Stripped66]

The color of paint has a slight effect on emissivity (how a material radiates heat), however, the color of paint has no effect whatsoever on convective heat flux (which our air-cooled engine's depend on); worse, the paint itself could be poor at conducting heat, which if painted on the case or cylinder cooling fins could (will!) hinder the transfer of heat across to the convecting surface.

Unless the paint you plan to use is as good as, or better at conducting heat that the material you are painting (e.g. aluminum), then whatever you gain in emissivity would be largely canceled out by it's insulative value as a conductor. Don't paint your engine case, cylinders, or heads; if you paint your cylinders to prevent rust, make sure it is a thin (THIN!) coat.
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[werka]

Basically adding paint makes the case slightly thicker (I know paint is thin). This is just another boundary layer that heat has to transfer thru before it touches air. If the case was made of copper which is a very good conductor of heat, would you want to paint that and expect better heat dissipation?

[vwracerdave]

If it's a trailer queen and all you are after is show trophies, then paint it. If this is street driven more then on and off the trailer, then do not paint.
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2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
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[Blaubus]

[Corwin]