I have found a few brand new castings to have porosity holes in them after they were torqued down. All of these heads were aluminum SB Chevy heads and were made overseas. These heads were “good” prior to proper installation.
More than once I’ve found brand new water pumps to have leaking seals at the weep holes. Air is much less dense than water, so any small leaks are easy to find. With my vacuum pump I can check all freeze plugs, galley plugs, intake and head gaskets (for sealing) and block and head castings.
For a test, we took a freeze plug and drilled a .006? hole in it and it failed miserably. We have even used the pump as a “reverse” pressure tester on cylinder heads where we couldn’t find an external leak, but knew the head was bad. It’s sort of a second opinion that confirmed our suspicions.
Jeff “Beezer” Beseth
Newtown Square, PA