"pores"????? We don' need no steenkeen PORES!!!

Listen guys. . THINK about this "pores" stuff a bit .. what exactly ARE pores???

A "pore" is that little gland in your skin that exudes liquids, like SWEAT, so that when it evaporates it will cool you off. That's what pores do. . Engines, and METAL do not have "pores". Pores in your skin also allow your skin to "breath" or to actually vent gasses and waste instead of letting it pile up inside near the surface. (anyone know what a pimple is??? A pore that could not breath properly )

Metal can be said to be "porous" meaning that it has imperfections or air bubbles in it after it is cast, and you do NOT want this to happen. This is an ongoing problem with metal castings, due to out-gassing of chemicals and actual metal vapors that leave hollow pockets or "bubbles/pores" inside the metal when it cools. There are no actual "pores" in metal. . there are imperfections though, and by golly if you seal these little pinholes in metal you are probably doing a good thing. There have been several instances of 3W crankcases developing air leaks due to "porosity" problems, because of hollows and pinholes in the castings that left weak areas that ultimately failed after heat cycling and vibration/stress. This causes leaks, and the only solution is to replace the part.

SOOO!!. . PLEASE remember. . metal does NOT have "pores" to clog in the first place!!! If it did, it would fall apart!! It does, however, have pinholes, imperfections, and alloy separation spots, none of which contribute to cooling the metal or radiating off heat, and all of which can be easily plated/painted with no problem.

Preach on brother KRIS! =)

I could just see it. . new motors could actually be "pimply faced" if they had pores!!! Older ones or those that are problematic could get to be a "Boil in the backside", and the ones with the least pores, and best performance, could be called "Smooth and creamy skinned" just like a beautiful woman. . one you want to keep around for a LONG time!!

Seems motors with machined billet crankcases have the best looking "skins" . .at least to me.

Think I'll keep a few around for a while.

Oops, should have asked an engineer or someone who has read a book.

All castings contain some porosity.
If you cut a section through a casting and polish the surface to a 1 micron finish and put it under a microscope you will easily see the porosity wherever it intersects your polished surface. The metal is only in danger of falling apart if the stress is too high, or if there is so much porosity that the metal looks like swiss cheese.

The porosity doesn't help to transfer heat. The little air pocket inside the porosity is a pretty good insulator compared to the aluminum matrix.

Painting a metal surface can prevent heat transfer (and raise the temperature of the part), because paint doesn't conduct heat as well as aluminum. On the other hand, a dark colored paint can radiate heat better than a bright metallic part. In the temperature range below 400F, radiation of heat isn't very important compared to convection and conduction to the airstream.

If painting the cylinders really raises the engine temperature by 40F, 3W would be smart to quit offering the fancy paint option.

I totally agree Diablo. it's been proven that dark colors have a much better heat transfer capability than even the dullest looking cast metals. Considering the layer of paint is only a few thousandths of an inch thick, its really too thin of a layer to do much in the way of "insulating" or acting as a heat blocking layer to keep heat in.

Certain paint products or coatings that are commercially available actually have a better heat radiation capability than bare metal. these coatings are used in many automotive and motorcycle racing applications to help dissipate heat and keep the metal itself cooler. "Moly" piston top coatings, components coated with refractory (but still "clear") platings, and even more temperature dissipative metal platings all help to offload heat from these highly stressed engines or prevent its absorption in the first place. Perhaps our engine manufacturers should look into this. I'm sure there are some power gains that could be economically incorporated into our engines that would involve nothing more than a moly coating on top of a piston or keeping the incoming fuel-air charge cooler for as long as possible.

IMHO 3W would never paint their cylinders if it raised temps more than a marginal amount. Someone is quoting figures here that has not done any real research. . sort of like those bogus Hp numbers we see or the claims of 106cc motors swinging 30-10 props at 6000 rpm. . . hard to belive ANYONE actually tried to foister THAT claim on us

BTW. . I've READ most of the books. . I just refuse to be limited by them. (don't you know Logic SUX??)

I agree Diablo,but for a gimic to help sell motors it works pretty good don't you think? It's not a bad thing to paint the cylinders if it is properly cooled,that's why proper baffling diagrams are mailed with the larger twin cylinder engines,atleast they come that way with the engines I have received.I could have gotten my 106 with painted heads but I asked questions on the process and downfalls of it and decided not to go that route.
It sure does look pretty though and that does help sell engines. Again it's not a bad thing unless you are not properly cooling your engine consistantly.

Anything that significantly raises the engine temperature is a bad thing. If it really raises the temp by 40F, I'd call it a bad thing. An optical pyrometer pointed at the engine surface is measuring the temperature of the metal. It's not measuring the temperature of the air. There is also a temperature gradient in the engine. The internal engine parts are hotter still.

The best analogy to understand heat transfer is electricity.
The temperature gradient is voltage.
Heat flow is current.
The metal is a resistor.

If an engine is making power, it's generating waste heat (over 60% of the energy of gasoline is waste heat). The idea is to get rid of that waste heat and minimize the temperature of the engine. Adding paint is adding another resistor in the circuit.

I agree whole heartedly and that's why I choose not to go that route. A.I. offers this process as an A.I Series Special and all it is is a little paint and polishing,nothing is done to the inside of the motor! it's all cosmetics,that's all and believe it or not it does help sell engines. Cactus will also do it if it is requested,but does not push the issue to help sell motors under the Cactus Series name!
My advice to anyone looking to buy the upgraded QS Series regardless of who you buy from A.I. or Cactus, ask questions on the paint process!! and not from just one person, make sure to get a second opinion it always helps.

Only problem with most optical pyrometers (laser temp guns??) that I can see. . you don't get a good reading of what's going on UP THERE while the plane is flying, by the time you land and taxi over the motor has had quite a few seconds (30-40) at low throttle during landing approach, and if you try to take the temperature with the cowl off the cooling airflow totally changes. Kind of a hard way to get an accurate measurement. Then, the ones most people buy make it hard to pick the hottest spots for their readings. Imagine the differences between the top of the head and the exhaust port area. Then, are you hitting the side of a cooling fin, the cylinder between the fins, perhaps someplace else?

As has already been stated, though, its very doubtful that the painted cylinders are being marginalized for cooling due to just the paint. I know that if I was an engine manufacturer I'd never do anything to make it harder to cool these things off. . There's already too many pitfalls and problems as it is.

I stand corrected (MILDLY) Diablo on the idea of "pores" versus "porosity". Every cast metal has some sort of porosity to it, it's the nature of the process, though some materials have a LOT bigger holes/voids than others. but. . "Clogging"?? uh. . . no

Is it worthwhile to take temps of the heads? If so, when and where? Who sells the device to do it_bob

I've never taken head temperatures, but have always ensured that I have proper duct work that forces the air through the cylinder fins. I look at how the engine is running in the air, and read the sparkplug color and exhaust outlet "sootiness" to determine how the mixture is doing, and leave it at that. As long as you have proper airflow over the fins, use a good quality oil that helps reduce temperatures (such as Amsoil 100:1 synthetic, which I strongly recommend and sign the praises of), and don't experience leaning out of the mixture, it's kind of hard to overheat one of these engines unless you really try to do it by severly overpropping them or doing extended torque rolls and hogh-power/low airflow maneuvers on hot, humid days.

A lot of people are buying the Radioshack infrared temp gun to check their temperatures. You have to get fairly close to the engine, but it's a pretty accurate piece from all accounts. Spots I'd check would be the exhaust port flange, opposite side from the exhaust, cylinder top next tot he sparkplug, and crankcase. Make a chart of these locations for EACH cylinder, taken on a cool day, and then do comparative readings to see what is going on. The crankcase should be substantialy cooler than the cylinder readings, with the hottest spots being the the exhaust area first, plug area second, and top of the motor third, this due to where the intake, power, and exhaust occur on the engine and the related heat of these areas.