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A liquid gasket does not require any punching of holes and you also don't need to make allowance for it's thickness during construction. When I do want a gasket that is what I use but often the metal to metal is good enough for air running and more.
Zee, Check the torque on the screws holding they cylinder onto the frame. If they are not evenly torqued the cylinder will cant and lock up the piston. It happened on my steam powered iPhone charger and I chased it for days before I figured out the problem.
Dont get frustrated, it will come together and you will learn a lot!