Low vacuum reading

What is a normal vacuum reading at idle for such a mild cam?

383/ .474 purple shaft/ Holley 600 DP/ stock distributor

Trying to get the 383 in my new Dart tuned right. Got timing set to 32* total. Hooked up vacuum gauge and was shocked to see 5" on the gauge. Adjusted mixture screws by idle speed as the vacuum did not change. Looked for vacuum leaks and found none.

Rebuilt the Holley and replaced the 6.0 power valve with a 3.5 power valve because of the low vacuum. I assume the power valve was open at idle before rebuild.

Motor has what I think is a screw in pcv on the pass side valve cover. I plugged that and the carbs pcv inlet and was able to get a 10" vacuum reading. Can a bad pcv drop vacuum readings like that?