Hi I bought a 1975 Monte Carlo that had a replaced engine and had been partially rebuilt. It has a GM Goodwrench 350. On the front right of the valve covers I believe is the PCV valve but what is the second hole on the left side and back of the engine but still on top of the valve covers. It is exposed and I feel like I should cover or know what rightfully plugs it? THank YOU

 

I'm sure you can still find them at a dealer or Auto shop. But I'd plug it. Keeps the dirt & water out.