i have a set off prostamped valve covers and they spit oil out the oil fill hole, right now i have rubber gromets in it to cover it up, do i need a breather cap?

 

I guess it's possible the fill hole is out of round. Have you checked the cap to make sure it's not cracked? This only started after you put the valve covers on?
IMO I'm compltely against breathers for street cars with the stock PCV system in operable condition. Completely unecessary.

 

it didnt happen before with stock valve covers, but the engine is completely changed, from then, when i pulled my motor i bent the stock valvecoveres. any other ideas, why are u against breather caps?

 

They're a vacuum leak into your system. They let unmetered air past the tb.

 

Because the stock PCV system is plenty enough to handle any pressure from inside the engine, I caution calling it "blowby" because some will deem that term automatically as being bad when even a healthy engine has blowby of some sort. Besides I think breathers look ugly on a street engine. Especially if one doesn't take care and constantly clean the dribble of oil vapors they create all over the valve cover.