Finding an internal vacuum leak

This test is too easy; put a vacuum gauge on the dipstick tube, then flip the PCV out of the valve cover but leave it attached at the carb, Remove the breather and plug all holes into the calve covers and CC.
Finally start it up and increase the idle rpm to at least 1200 to 1500 while watching the gauge.
There should not be any vacuum there now.
There should be a pressure building up in there which you must not allow to got past about 3 psi., or it could push your rear cam plug out.