cam gear timing 1936 LB engine

[FRANK PKNY]

I'm working on a 1936 lb engine that was rebuilt and sold to my customer. I think the cam gear is out of time, after installing the engine in a test stand while cranking over I'm getting compressed air out of the intake manifold and vacuum in the cylinders. Is it possible to change the cam timing without pulling the entire cam, by removing the cam gear and reinstalling the fiber gear? If so how do you remove the fiber cam gear?