Prior to the PCV system SBC motors vented the crankcase threw an Outlet tube usually found on the back of the intake manifold next to the distributer ...
Just to clarify;
Prior to the PCV systems - there was a "Draft-tube" system that allowed vapors to flow from the fill tube vented cap inlet, through the block and be drawn out of the draft-tube by the negative pressure differencial at the tube outlet. The vapors and crankcase bi-products were dumped into the air flow under the vehicle.
These draft-tube systems were never installed on Camaro engines from the factory.
The 'outlet' for the crankcase vent was cast into the rear of Pre-1968 blocks (for automotive use - marine, industrial and truck continued for several more years) - not the intake manifold.
Inlet vent air to the crankcase entered via the cap on the oil fill tube on "Open" PCV systems and through the rear vent on "Closed" PCV systems (a reversed flow to the 'open' venting design).
The PCV valve was mounted in the rubber tubing leading from this rear vent hole to the intake on 1967 "Open" systems.
The PCV valve is screwed into the fill tube and routed to the intake via rubber hose on the 1967 "Closed" systems.
There was also an oil-seperator installed internally in the block lifter galley (below the manifold) that caught most of the oil out of the vapors exiting the vent hole.
1968, and later, automotive blocks do not have the rear venting provision hole and used the valve cover holes to allow crankcase vapors to be vented to the intake to be burned off during operation.
The passenger (right) side is the inlet side to the crankcase vent air flow of the post-68 PCV systems and the PCV valve is mounted in the Drivers (left) side valve cover (or in the tubing run of a few set-ups) as the vapor outlet to the intake system for the vapors to be burned.