Stupid question time (valve cover version)

[DAVID_T]

What are these tubes/ports on the valve covers called, and what is the part called that connects to them? Sometimes I'll see them in photos capped off, and other times connected to a hose that I can't see where it goes. Do I want them connected to something? I'm having issues finding the answer on a search.

Thank you in advance.

151674
151675

[egchewy79]

those are called breathers. they allow for positive crank case pressure to release to the atmosphere. the hoses you see attached are usually connected to the throttle body or air cleaner for a PCV system. The PCV valve is placed in the valve cover opening, often attached to a catch can and then the throttle body, to collect any of the vaporized oil/gases so they don't directly feed back into the throttle body to keep the top end of your engine a bit cleaner. if running a PCV, you put a breather with a filter on the other valve cover. PCV system cleans up emissions a bit and prevents oil from just blowing/misting all over your valve covers with traditional breathers.

[narly1]

They're called breather/filler caps.

They are available in versions with and without hose connections.

The inside of the caps on the ones without hose connections are usually packed with some form filter material to catch the oil component of the vapours that build up inside the valve cover.

The ones with a hose fitting may or may not house a PCV valve. The hose is meant to connect to the clean (inside air filter) side of your air cleaner.

Failing to manage vapour build up (pressure) inside an engine can lead to a host of other issues. The worst one IMO being rear main seal leakage.

On the subject of PCV valving I found this website to be an excellent resource: http://mewagner.com/ .

In fact I have purchased one of their PCV valves for my 302 build.

Earl

[kgkeys]

On an EFI engine, you can't have an open breather. The air has to be "metered" by the mass airflow sensor, so in that case, you'll see a tube running to the intake, somewhere after the MAF, instead of an open breather.

Kyle

[Blitzboy54]

The incoming air goes to your air cleaner. The PCV valve is connected to the vacuum source on your carb/sniper/efi..etc. NY State requires a PCV system on the 302.

This pulls crank case air out and puts it back in the engine for combustion. It is replaced with fresh air that comes through the filter. This isn't the best photo but you can see on the passenger side there is a 90 deg check valve. That has a hose that goes to the sniper vacuum port. The other side has the fresh air coming in from the cleaner.


https://thefactoryfiveforum.com/attachment.php?attachmentid=151094&d=1626909318

[Norm B]

Good explanations have been given already but, for those that do better with pictures (like me), here is a simple diagram with a pretty good write up.

HTH

Norm

[Lickity-Split]

Great attachment, Norm.

[narly1]

Good explanations have been given already but, for those that do better with pictures (like me), here is a simple diagram with a pretty good write up.

HTH

Norm

One small point about that diagram (and I might be splitting hairs here so free to tell me to "GTH", LOL) is that it depicts the tube running from the breather to the air cleaner as being connected to the outside of the air filter and thus sucking dirty air into the engine as opposed to drawing clean air from the inside of the filter.

[Norm B]

I thought that too originally but, the red area in the middle top is labeled “air input” and the description states from inside the air cleaner for filtered air.

Norm

[DAVID_T]

Thank you very much for the input! I found the part. You are very much appreciated, gentlemen.