Valve covers are baffled if you have
oil coming out you have a blowby prob.
Here’s a photo of a 73 Ford 390 FE driver side and 86 Mustang 5.0 HO pass side.
The 86 5.0 driver valve cover has no holes.
My early Chevy small blocks had a PCV in the vent hole next to distributor and a vented cap in intake manifold
oil fill tube. A big
oil separator bolted in the lifter gallery. The valve covers had no holes, said Corvette on them, good times