engine running lean means it is running hot??

Lean == greater air-to-fuel ratio than rich. More air means hotter. Have you ever used a cutting torch? Same principle. A super-lean mixture can melt a hole in a piston.

Amongst many things that are involved in this, combustion by-product helps to carry away heat through the exhaust. This by-product of combustion (which is very different when the fuel/air mixture is not correct) is mostly water vapor by this time in the combustion p[rocess. Usually it is only a tiny bit but it makes a difference. This is probably one of the most "missed" items in discussion of cooling a cylinder............timing is not everything, but can help make up for some of this, either in valve or ignition timing, on most

*watercooled*, carburetted engines. Be careful how you apply it to ACVW's.

Also as JS stated the heat of the burn inside the cylinder is higher when the fuel air mixture has less fuel and more air.........this only to a certain point , as there is a point where the fuel air mixture is too lean to iginite under the given conditions in your cylinder/s. It is a common occurence though.

The funny thing about this is, in most carburetted *watercooled* engines, you can run higher octane fuels and advance the timing and get better gas mileage. Or if you like you can lean down the mixture a bit and get a bit more pep.

If you do this in your ACVW, you will burn a hole in the #3 piston face post haste. This is due to cooling issues and the hotter/faster flame front. The valve for exhaust on #3 will not be open long enough to allow the heat produced to be pushed/sucked/absorbed from the cylinder. The temp of the flame front, the burn rate of the fuel air mixture, .................all of this and more will cause you issues on the bug engine. Whereas if it were any other engine with carb and

*watercooling*, there is a much wider range of abusability or as some may call it a margin of error.

I am sure I am not covering all of the things that are involved, so i left it open for further discussion. Many items will be involved and A thourough understanding of the combustion process is needed to make decisions on fuel/air mixture adjustment, ignition timing, valve timing, porting, etc......................LOL

Sorry if this is too much, but it is really, like I said before, just a start,...........the tip of the iceberg so to speak.

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Evaporation. When a liquid is converted to a gas, it removes, or carrys away heat. When you burn fuel vapor, it creates heat, it also absorbs heat. Less fuel vapor, less heat is absorbed. This is one of the problems with running propane, since it's converted to a gas by the time it gets to the combustion chamber, none of this "cooling" happens, and you eventually burn something.

--Mike