Originally posted by Speed
If you are talking about the Metrakit Pro Race, yes it recess into the cylinder head to help seal it better for water leaks from o'rings.
I would try the Metrakit Pro Race Exhaust. The Cylinder + Exhaust seem to work out good. I clocked a Beta Temp modifed to Liquid Cooled in sprint race with my radar gun. Here got 85mph. He is using a complete Metrakit motor.
I am suprised not too may persons use the Pro Race Kits over in Europe. It seems much better than Hebo Maston. I have tried both and I've visited the factory.
Note: Metrakit rate their Pro Race Kits at 15,000rpm. When I raced their Zip in Spain, they ran it at 13,000rpm. Their Zip was FAST indeed, I must be honest!!!
Speed