Piston windows

[SLORYDER]

I realize that they flow the air/fuel mixture somehow, but that's about it.

 

Do they just draw air through them when aligned with the intake port or are they fed by the boost also?

I also noticed the bottom of the piston shirt on the intake side has grooves cut corresponding to the intake ports; I assume this is to increase intake duration. It would appear that intake duration is 360 degrees and there is no point in lowering the intake port. Is this correct?

Edited October 28, 2009 by SLORYDER

[jbooker82]

They allow air and fuel to be drawn in to the engine and crank case. When the piston goes from bottom dead center to top dead center the volume of the crank case increases. That is what draws air and fuel in from the carbs. When the piston traves from top dead center to bottom dead center the volume decreases. So the reeds shut and the crank case gets pressureized, unitl the transfer ports are opeand.

 

The ports in the piston dont have to close because the reed cage is what stops the air and fuel from being blown back out the carburetors.

[SLORYDER]

So increasing intake duration is not really possible?

[jbooker82]

The main intake duration is set by the port highs of the transfer ports. Those are the ports that fill the cylinders. As for changing the port hights of the intake ports I dont know about.

[AKheathen]

i wouldn't mess with it too much. there is not enough gain to warent weakening the pistons and significantly decreasing the life. just match the cylinders when you are working on the flow....