I am wondering how common this problem is. It is likely that most of us have sent cylinder heads to a shop for a valve job, installed them upon receiving them, and run the engine that way. On the contrary, I think few of us have pressure or vacuum tested the cylinder heads after the work was done. The only reason I did so was to test the plumbing for the EFI's MAP and IAC (Idle Air Control). While testing that plumbing, I found leakage in the manifold gaskets and fixed such with thick gaskets and sealant. While continuing the testing I found the leak in one valve seat. Throughout this testing there have not been any leaks in the plumbing for the MAP and IAC. I am somewhat reluctant to tear down a sealed manifold and cylinder head just in case one valve might not seat once the engine is running. I am now setup to test the valve's sealing ability at any point in time. I am inclined to run it as is, and test the valve's seal after break-in. Over the years I have become somewhat accomplished at removing Pantera cylinder heads in the car and have a special adapter for my engine crane that handles cylinder heads nicely. I think I will roll the dice and hope that the valve seals. If it does not then I will pull the head in the car and lap the valve.
Thank you for your input on this.
Here are photos of the plumbing that I was testing. It is the black tubing and push to connect fittings.
