Is it possible to have too much engine breathing?

[Nads]

I just bought a pair of lovely Cal Custom valve covers for my Chevy. One of them has a breather and the one's drilled for one. The engine's a '62, so it has a rear breather as well as the oil fill tube/breather.
Do you think I should block off the valve cover breathers, or is it okay to leave them on?

Thanks.

[Rand Man]

What condition is your engine? If the old gal is suffering from blow-by. You my end up with more oil film to wash off. If you care.

[slammed]

Sweat band's for your wrist work well in keeping the breather from 'weeping' oil film.

[Nads]

The engine's brand new, freshly rebuilt, it doesn't blow oil out of the existing breathers. The front breather fumes when the engine's shut off, that's normal I guess.
I don't like the looks of the breathers all that much, I think I'm just gonna make a couple of blanking plates out of aluminum.