Since I gave up some power by adding a 1/16″ head shim I decided to improve air flow through the engine by doing a minor porting job. The engine now has a total of 1/8″ head shims which is the maximum and will make the engine easier to pull over. Since the engine runs so well I am not going to take it apart so I can’t do my normal porting job but I can smooth over the dead sharp corners at the intake ports without disturbing the chrome plated cylinder wall.

I have been using the same Chicago Pneumatic die grinder and carbide burr for close to 40 years. Fluid Dynamics was my favorite class in college and served me well when I designed a large industrial flow bench for a pipe fitting manufacturer. I built my own flow bench for SCCA Formula Vee race car carbs and calibrated it to the industrial flow bench. I still have the calibration plates. I used the flow bench on Rokon carbs and cylinder ports years ago. This minor mod and a reed cage mod is worth about a 10% increase in air flow. That translates to a 10% increase in HP on an engine dyno.

I did the port job with the piston closing off the ports so metal would not get inside the engine. I stuck a balled up paper towel in the opening into the crank case.