How many cams does a cylinder need?

Each cylinder basically has four valves.

There are three to five valves in each cylinder, and double overhead camshafts are needed. At present, most engines adopt double overhead camshaft design, and each cylinder basically has four valves, two intake valves and two exhaust valves.

For example, if a V8 engine adopts DOHC structure with four valves for intake and exhaust, two rows of cylinders need two timing chains, four camshafts and 32 valves, and the final engine volume and weight are very huge.