Hello I am working on a 1955 272 engine that was rebuilt years ago and never started , I have a preoiler hooked up to it and have cycled oil  through the engine a few times. I have not yet been able to get out of the rocker shaft , I hear oil gurgling in the engine and the oiler drains quickly but no oil on the rocker shaft . I have the oiler hooked up where the oil pressure sending switch is . thanks for any answer