Strange exhaust port factory casting on swap meet engine

[Evanfrucht]

Hey does anyone know if there is some sort of performance related design aspect behind this? The exhasut port has a factory left obsruction (little vertical bar that was never ground out) I think this in an older Chinese kit engine based on the markings on the rod and YouTube video I watched.

 

[crassius]

is it 47mm, or 40mm, or 45mm?