. 14 mm at end of gauges to spark plug hole. Disconnect exhaust and intake. Get help.plugging holes with fingers but some corks or other might hold TOTALLY, and have 7 psi flowing in. Spray dilute baby shampoo over engine head gasket base gasket seals if u suspect a case leak everywhere and watch for expanding bubbles. It passes if it holds 7 psi with no bubbles. If it passes the likelihood of a leak is very low. Some folks will say that a classic leak down also instead of pumping air in at 7 psi creates a 7 psi vacuum. So there are various vacuum devices at say harbor freight which u can rig to do that if u want to go both ways. I can't argue that both ways is even better. Because it is.
Or alternatively spray some combustible substance like brake or carb cleaner. Please don't do that in NorCal so I have zero chance of having to have to take care of you in our burn unit.