What's the meaning of “ported” in this sentence?

Question

I found the word "ported" in a sentence describing a motorcycle, but I don't understand what it means:

A beautiful machine, it was ported and polished, with high-compression pistons and rings, a welded crank, and a racing clutch.

Answer 1

Porting an engine means to modify the areas (the ports) inside the cylinder head around the inlet and exhaust valves to improve gas flow and thus obtain more power because of more efficient fuel combustion and exhaust gas evacuation. This is typically carried out by removing metal appropriately, and smoothing (polishing) metal surfaces. It is a form of "tuning".

Porting and polishing