Jerry is correct the right stuff works better. Take a pointed prick punch and a hammer and make little indents on the rails of the block and bottom of intake this will give the silicon something to hold on to.
The oil thing I had a buddy have the same issue he put the rocker arm shaft on one side up side down. Filling the head with enough oil it could not return fast enough and was overwhelming the valve seals.
When will yours smoke the most. If its when you let off the gas that's when you have most vacume that could be pulling it through the guides or your intake issue but if its the intake you would not be able to idle very well .not sure what or how big your race cam is you should cam you engine on the RPM range you intend to use. Street cars need some vacume They should have PVC system. Race cars just run a hose from breather to one way valve to the exhaust or have a high dollar pump ether way you got to get the pressure out or it will push its way out through the seals.
I use a moroso oil catch between my pcv valve and carb to catch any oil that might pass by the pcv. Don't want it in the intake after 500 miles open the valve and drain it not much but any is better than in the intake.. I have zero oil drip from breather.