Porting a motor can have a dramatic effect on an engines performance. It is not necessarily increasing the port size though. Best of all it adds performance but costs nothing, unless you screw it up in the process.

Porting is just one part of engine modification. With my motors I do usually start with port matching. This matches up the paths in the case with the opening to the ports in the sleeve. Changes can either be done to the case or the sleeve depending on the problem. This almost never means changing the actual size or location of the port face in the sleeve. The port face is the actual surface opening in the chrome inside of the sleeve. Modifications to the brass on the outside of the sleeve are the most common.

Then modifing the path that the air fuel mixture travels around the sleeve is second. Thinning out the area at the bottom of the sleeve where the air/fuel mix travels from inside the sleeve around the bottom then up into the ports, and finally into the combustion area.

Then lastly changing the exterior shape of the port to increase port volume, and or increase air/fuel mix velocity.

The last holly grail of engine modification is working with the engine timing and overall port surface volume. This can provide the most gain in engine power, specifically the duration of intake timing.

You can see in this picture how the bottom of the sleeve has been thinned out to gases to move around it faster, and also the groove that has been cut into the edge of the port to increase port volume, while increasing the speed though which gas will pass when entering the combustion chamber. If the entire face of the port had been thinned out the velocity of the gasses would have been decreased and even though the port was larger less gas would flow through it due to the decrease in velocity. Darn can't seem to get the pic uploaded

Rick RBMods