Shrouding in the chamber is only half of the problem with inline-valve engines like these running large valves and lift. (Seasoned gearheads will already know this) Poke the valve out past the chamber and it runs right next to the cylinder wall. I was inspired to take a picture after seeing some that MDB showed a while back.
This is a fairly extreme example with a 64mm bore, 28.6mm intake, and stock exhaust. A 32mm valve won't come close to fitting without hitting the block. Boring out to the stock GX160/200 size of 68mm would help significantly. Going all the way to 76mm(3.00") would be better still.
This is why canted-valve heads are preferred in most forms of racing that allow them. The valves are angled so that they open toward the bore center and away from the cylinder wall. This also provides for using larger valves than would otherwise be practical with an inline head. Offset guides are another old trick for running bigger valves when bore size is a limiting factor.
Food for thought.
This is a fairly extreme example with a 64mm bore, 28.6mm intake, and stock exhaust. A 32mm valve won't come close to fitting without hitting the block. Boring out to the stock GX160/200 size of 68mm would help significantly. Going all the way to 76mm(3.00") would be better still.
This is why canted-valve heads are preferred in most forms of racing that allow them. The valves are angled so that they open toward the bore center and away from the cylinder wall. This also provides for using larger valves than would otherwise be practical with an inline head. Offset guides are another old trick for running bigger valves when bore size is a limiting factor.
Food for thought.
