A crankcase MUST be ventilated, either with a road draft tube or a PCV, and it also must have a source of fresh air- - -a vented filler cap, slots in the valve cover on the 6-cylinders, or a tube from the air cleaner to one valve cover with the PCV in the other side. The drilled carburetor stud is the vacuum source for the 283 and 327 vacuum advance- - - -those distributors are set up to use full manifold vacuum. All the 283's and early 327's I've worked on have a hole beside the distributor for the road draft tube. It connects to a canister-type vent in the pushrod valley. It's possible to fit an adapter there for an inline PCV valve that uses 3/8" rubber tubing, attached to a 1/4" pipe thread vacuum port in the back of the carburetor or in the manifold just ahead of the distributor, the same one that powers the brake booster. Then the incoming air can come from the vented oil fill cap, or a late-model valve cover with the grommet and a tube to the air cleaner housing. It's got to have both fittings- - - -PCV and vent, to work right.
Your white residue is condensed moisture, a normal byproduct of burning the hydrogen in gasoline. Hydrogen plus oxygen- - - - -water vapor! Whatever small amount of combustion gas that gets past the rings simply has to be vented!
Jerry
