Flow loss

[superbike]

I have been messing around with some junk heads of the 4v type with cloverleaf conbustion chamber.

I found low lift flow by opening up the throats with a 75 cut down into the aluminum and high lift in the short side radius. I then thought i would remove the 30 degree top cut to a 15 degree wich would also deshroud the valve a little as the cutter is longer. The result was a small gain below 4mm and a big loss from 9-12mm.

I really did not think it would have this effect.