Hey guys sorry for my ignorance but I want to know a bit more about the PCV and why our trucks have a oil breather? Is there any good post on this subject and how to make sure your truck's system is properly setup? Thanks as always. Can the PCV be removed without any negative effects on the engine? Teach me! lol

 

Franklin2 & 81-f-150-explorer have written some good explanations within the last 18 or so
months. In general, no, it's not a good idea to disable/remove it, it returns blowby gasses to
the combustion chambers and its presence has no negative effects anywhere.

 

On these trucks, the PCV (Positive Crankcase Ventilation) system is simple. On V8s, you have a PCV valve in one valve cover, and it's connected to a vacuum port on the engine (such as the vacuum tree on the back of the intake manifold). This valve allows the engine to draw out combustion gases ("blowby gases" as ctubutis said), moisture condensation, and other junk and burn them off in the combustion chambers.

On the other valve cover, you'll likely have a combination oil filler cap/oil breather. Some have a PCV valve that fits into them and is replaceable, while others have the valve integrated into them. This oil breather connects to the air filter housing and allows clean, fresh air to be drawn into the valve cover.

The 300 would have the PCV valve and breather cap on its single valve cover. Or it might have two PCV valves and a simple cap for the oil fill opening. I've never worked on a 300 so I'm not sure. lol

So basically, fresh air is drawn in through the oil filler cap and combustion gases and other contaminants are drawn out through the PCV valve. There are no negative effects to keeping this system in place, and there's no power loss as a result of keeping it. It would probably cause problems if you removed it.


As far as having it properly set up:

- Make sure your PCV valve(s) are clean and in good shape (if you shake the valve itself and hear it rattle, it's probably fine)

- Make sure your oil breather cap is sealing to the valve cover well

- Make sure you have the filter in the air cleaner housing for the breather cap (you might not have this filter if you have fuel injection), and

- Check the hoses connected to the PCV valve and breather cap and make sure they're in good shape.

The components of the PCV systems on these trucks are cheap to replace, so it might be a good idea to just go ahead and replace at least the valve(s) and hoses as preventative maintenance.


Finally, on my truck, I have the PCV valve connected to the vacuum tree on the back of my 302's intake manifold, so it's getting a constant vacuum. The oil breather cap is connected to my air filter housing. It's a carbed 302.

 

Alright so I recently replaced my valve covers. Did I put a PCV where the oil filler cap should be?

And for the PCV side I took it from the old valve covers and hooked it back up like it was on the new valve cover.

(On the top of the cover you can see it.)

 

I miss road/down/vent draft tubes.

 

First pic:

That's one of those integrated valves I mentioned. Does your air filter housing have a place on the bottom for the oil breather cap hose to connect to? If not, you'll probably need a cap with a filter integrated as well, and it wouldn't need the hose. (I've had a hard time finding any factory style twist-in caps with the integrated filter...most everything I see is the push-in style like how the PCV valve fits in.)

Second pic:

That PCV valve looks as old as Moses...I might would suggest picking up another one. :P Like I said, they're cheap as dirt.

BTW that is a sharp looking set of valve covers, and the air filter goes well with them.

 

Thanks Kirby! Yea the air filter housing has like punch outs in the back... so I should run a house from the oil filler cap to the back of my air filter housing? I'll run by auto zone and pick up some new pcv valve then. Thanks for the compliment and the help! I plan on getting some red spark plug wires to match the filter I think it'll look good.

 

You're very welcome! And I might have to get me a set of valve covers like those. Where did you say you got them?

Yep that's what you need. Not sure exactly how a hose would connect to just a hole though...do you have the package and whatnot that came with the air filter housing? Might be some sort of little clip or something for this. And yes, you'd run a hose from the cap to the air filter housing.

I think that'll look great. Is that a K&N filter?

 

Heres the link to them. I got them from Summit racing and i'm very pleased! Ford Racing M-6582-A301R - Ford Racing Aluminum Valve Covers - Overview - SummitRacing.com

I don't think it came with anything but i'm sure I can throw a rubber push in gasket and a elbow in it.

Its actually made from Spectra but I'm planning on getting a K&N filter shortly.

 

The hose from the oil cap to the air cleaner looks like a homemade job. My '66 with a 240 doesn't have that. The oil fill cap is solid. I do have a couple of newer valve covers that have three holes in them.

 

If you remove the cap and flip it over on the bottom should be a bunch or holes.
This lets air into the motor, unfiltered as that is how it was done back then.

Does your air filter have a place to put a hose to pull filtered air from like the newer trucks have?
If so you could then use a cap that you can put a hose on and run the hose from it to the filter.
OR
Get a newer valve cover with screw in fill cap and has a hole for the fresh air hose.
The PCV is behind the air filter, picture of my 81 F100 motor.


Dave ----