Probably not. When I bought my Swinger, i noticed that it had oil leaking at the valve covers and distributor base, then noticed that it didnt have a pcv valve installed. So I put new valve covers on, and plumbed in a pcv valve and low and behold, the leaks stopped due to lower pressure inside the motor, and it made no difference to the way my engine ran. BTW, Im only running a pcv valve from valve cover to carb base, I dont have a breather from the other valve cover to air cleaner, but I do have a vented oil filler cap, same system as what @66fs mentioned.