Oil Cap Filter?

[3800_Firebird]

I've been seeing this around a bit. It looks like a miniature air filter mounted to the oil filler in place of a solid cap. Sorry I don't have pix to show.

I'm wondering what the idea of having one of these is. Might seem mundane but I have no idea why you'd want a vent on the oil filler.

[Trash man]

PVC system, most run back into the manifold or intake, if its the intake, alot of aftermarket ones dont have a opening so u just throw a filter cap there

[3800_Firebird]

So in the case of my 3800, where the pcv is practically in my intake, would there be a benefit to venting the valve covers?

[Rob B (shoebox)]

So in the case of my 3800, where the pcv is practically in my intake, would there be a benefit to venting the valve covers?

None, whatsoever. The PCV system is the most effecient in removing harmful gases in the crankcase.

I think what you are trying to describe is a breather.

[Injuneer]

The PCV system is "closed". The air that is used ends up in the combustion chamber, so it has to be measured. If you "open" the system with a breather, you defeat this feature, and gain absolutely nothing.

[Wild Willy]

Back in the 'old', pre-emmission world, the crankcase was just vented to the atmosphere. Every time a piston travels down, it pressurizes the crankcase- They used to just put a simple filter there to keep out boulders and large flying insects.

With the advent of emmission controls, all crankcase vapors had to be vented back into the intake, and burned. The beginning of the PCV system (positive crankcase ventilation)

On a tangent, I have found, doing many engine swaps between various year engines and bodies, that, if you hook up the vacuum lines wrong, you can make some really interesting whistling noises under the hood-

[3800_Firebird]

The PCV system is "closed". The air that is used ends up in the combustion chamber, so it has to be measured. If you "open" the system with a breather, you defeat this feature, and gain absolutely nothing.

I figured, but I was just curious why you would want to vent the crankcase that way in a modern engine. This was on a 3800 II supercharged, transplanted in a Grand Am. I haven't been able to relocate it, I more or less stumbled across it.

Thanks guys! That satiates my curiousity.

[Joshu]

So if i threw one of these onto the hawk, nothing would happen? I just think it looks better than having the cap on there.

[Rob B (shoebox)]

So if i threw one of these onto the hawk, nothing would happen? I just think it looks better than having the cap on there.

Nothing, no. You'll cause the engine to pull in unmetered and less filtered air into the engine. The computer will also have to make a small compensation for the change. The PCV system works better than any breather. You'd be taking an efficient system and making it a poor one (to the long term detriment of your engine). I can't imagine that the oil cap is so ugly, that you would want to do that.