When I Pressure test an engine I use a sheet of rubber under the exhaust spigot with three holes punched for the ex studs and snug up the bolts. I have a aluminum bung I made for the carb side. I pressurize it with a harbor freight radiator tester and an adaptor I made for the spark plug. you can use anything to pressurize the cylinder, I use to use a old squeeze bulb and gauge from a blood pressure cup. just be sure the ports are open or it will take a minute to stabilize a reading if all the air has to pass the rings.