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There is not a pinch of $hit difference in the heat transfer from a painted engine and an unpainted one. I don't know why people keep dragging this subject up over and over again. If you want to paint your engine...have at it. It will not change the reliability of the engine one bit.

George Ryals wrote:There is not a pinch of $hit difference in the heat transfer from a painted engine and an unpainted one. I don't know why people keep dragging this subject up over and over again. If you want to paint your engine...have at it. It will not change the reliability of the engine one bit.

You may well be right, but I'd feel a bit more confident if your argument contained as much evidence as it did adamance. Hell, any would be nice.

One of the things I remember from College classes was that the color that was the best obsorber of heat was also the best radiator of heat. Now if it makes a difference I don't know, but I have seen way more black barrels that any other color, same goes for radiators too.

That's true. The emissivity of black paint is very much higher than bright alloy and if that was the only mechanism for heat transfer black would be much superior. But radiation is only one method of heat transfer. Once the bike is moving most of the heat is lost by conduction due to air flow which probably makes the advantage of black much more (pinch of $hit) marginal. In fact a layer of paint acts as an insulator where conduction is concerned. Who knows if that is out weighed by the emissivity. Then there's the the reduced surface area of a smooth painted surface vs rough cast. Lots of variables but I doubt paint makes a measurable difference one way or the other.

Back in my High school days we used to strip the paint off of the radiators on our hot rods and polish up the brass. A mechanic once told me that that was a dumb idea because it reduced the cooling ability of the radiator........ because black paint transferred heat so well. It sure looked cool when the brass was all shiny, but I often thought about his logic over the years. It seems clear to me that when moving air is the primary method of cooling then bare metal is the way to go....anything over it acts like a windbreaker. Perhaps on a stationary object the black paint would somehow aid the process, but that is not the case with motorcycles or radiators.
Ceramic coating on the exterior of a cylinder head would hold in heat (no matter what color). Ceramic coating is not paint and is designed to withstand high heat and insulate.
The mismatch of your heads and barrels is caused by age, heat, and alloys. After many heat cycles and exposure to the elements the barrels will patina, no matter how clean you keep them. There are trace elements in the aluminum castings that will change the color over time. Still, they never will match perfectly, nothing was meant too on these bikes.

Harry Pellow famous air-cooled Porsche mechanic did not address paint, but did say chrome plating engine tin caused the engines to run way too hot! He was an nuclear engineer also.....

Here are the results of vapor blasting.

http://beemersandbits.com/2012/05/vapor-blasted-heads/

I'm leaning on having them clear coated by a hot-rod shop that uses something that doesn't effect the cooling/dissipation (supposedly).

-Josh

My 1070 R90/s Replica has had the Seibenrock cylinders powdercoated satin black. I am not aware of any overheating issues, and the powdercoat has lasted well over the last 3 years or so.
I'm off to Spain on Sunday so with any luck might get some reasonable weather, it has not stopped raing in the UK since the 1st of April.

Charles

The last authoritative work on air cooling I can locate was a paper by Mr P. V. Lamarque B.Sc, A.F.R.Ae.S. which was published in the I.A.E.Journal in June , 1943, a digest of which was prepared by Phil Irving and published in Motor Cycling on July 22,1943 under his Nom De Plume of Slide Rule.

The relevant passage is - " With regard to surface finish a coat of smooth black enamel is an advantage, provided that it is very thinly applied, whilst a coating of oil makes little difference either way to the heat dissipation."

Phil went on to include a black coating in his design of the Vincent Black Shadow and Black Lightening motorcycle engines , and from all reports the result was more than satisfactory.

Roy Gavin wrote:The last authoritative work on air cooling I can locate was a paper by Mr P. V. Lamarque B.Sc, A.F.R.Ae.S. which was published in the I.A.E.Journal in June , 1943, a digest of which was prepared by Phil Irving and published in Motor Cycling on July 22,1943 under his Nom De Plume of Slide Rule.

The relevant passage is - " With regard to surface finish a coat of smooth black enamel is an advantage, provided that it is very thinly applied, whilst a coating of oil makes little difference either way to the heat dissipation."

Phil went on to include a black coating in his design of the Vincent Black Shadow and Black Lightening motorcycle engines , and from all reports the result was more than satisfactory.

That's it, then. See, MS, here's your "evidence." Its Vincent's fault.