removing valves 3.75 hp side valve?

You're right, there is a plate that hold onto the valve stem.
With the valve in the closed position use two screw drivers to raise this plate up towards the top of the engine. After about 3/8 of an inch the plate will slide to one side or the other. Once it's slide over let it drop and it will fall to the lower end of the valve stem and the valve will pull right out.

Good luck, Phil

Phil G
February 2011