unshrouding exhaust valves

I should explain the cam, it's a reground stock roller I'll use for now. I want to get the motor up and running and I've put a lot of money into it so far. I was going to use the 308 heads but got a great buy on new magnum bare heads. The 308's are 73 cc's and would have been no problem. They just needed new valves, springs etc. I put the work into the new castings. I still have to get a clutch and clutch linkage for the 4 speed.