Sounds like you might a a couple of problems.....fuel in the
oil, could be a ruptured diaphram in the fuel pump. You don't say what the plugs look like. If I'm not mistaken the 600 Holley has a metering plate on the secondaries, so you'll need the PV... use a 2.5 as suggested above...that's all I ever use. Check out the fuel pump, then start looking at plug color and play with jets.