That should be as simple as going to the parts store and asking for a PCV valve for your exact application.

 

The hole originally had a rubber grommet in it. Either for the elbow that was posted, for a hose to go to the air cleaner, or a grommet to hold the PCV valve itself.
The engine doesn't care whether the valve goes to the passenger side, or driver's side cover. They connect to the same crankcase.

Speaking of the passenger side... What is inside the other cap? Is it empty, or does it have some type of filter media as well?

Even with a PCV valve, you might still get vapors coming out of an open port. But with a good working PCV system, that is kept to a minimum, or eliminated completely as the vapors all get sucked out through the PCV valve.

I think it's been mentioned, but just in case, yes you can. You can actually use either of the large ports for your vacuum to the PCV valve. In some cases, it's a matter of whichever one is most convenient.
Looks to me like the rear one is most convenient to the brake booster, and the front one would be most convenient to the PCV valve.
I don't know if sucking into the primary section, or secondary section, has any advantage, or disadvantage to the PCV OR the idle quality. But either one will do the job.

Or the rear port...
And to be sure we're on the same page, that cap you have there now is NOT appropriate for a PCV valve. It's most likely got a filter material inside, but there is no hole to insert the valve into that I can see. So you either have to pop that out to see if a valve can be inserted directly into the valve cover, or if you will have to use the one on the driver's side instead. OR, if you have to buy a new grommet, or oil filler cap of the appropriate design to make the system work.
Over the years in question, Ford used at least two different size/style caps for the PCV valve. And different ones for the return vent.
Your driver's side cap might work, but it's not currently set up correctly for being either a valve holder, or a filtered air return.

Here's a pic of the "low profile" version that we sell. In the pic it's set up for the breather. In the case of my '71 and my '79, it held the PCV valve.



On Broncos with 289's and 302's, Ford used the passenger side valve cover for PCV duties, through the '70 model year. With the valve inserted directly into the cover. The driver's side had a tall cap with a tube to the air cleaner housing.
In '71 they changed to this lower profile oil filler cap, and inserted the PCV valve into it instead, and ran that 45° elbow directly iinto a grommet in the passenger side valve cover.
Same for the '78 and '79 full-size trucks.

I don't know if the openings in your valve covers are the same, but Ford did use similar methods for many engine families over the years.
Someone mentioned early on that it looked like you had two driver's side covers. You might want to remove the caps from both, and post pictures of the openings. Then those that know these things the most can comment on any differences.

As tbear mentioned, it's not getting actual manifold vacuum from the air cleaner area, but you can certainly use "vacuum hose" to do the job. But whatever you do, do NOT leave that cap on the driver's side as it is now. As a clean air return, the filter media inside it is an absolute minimum to keep stuff out of the crankcase. In fact, it's less than a minimum. I don't think that's what it was intended to be. Ever...

As mentioned, just get the one for your truck originally. You may still have to find the right way to mount it, but at least it will be the correct calibration for your engine as it left the factory.
Adding a 4bbl carb should not make a big change in the need for a particular PCV valve calibration, but changing camshafts and such may very well change things enough to require a little more searching on your part.
Luckily they're still inexpensive relatively, so buying two or three different ones is not a bank-breaker.

 

I don't know if the openings in your valve covers are the same, but Ford did use similar methods for many engine families over the years.
Someone mentioned early on that it looked like you had two driver's side covers. You might want to remove the caps from both, and post pictures of the openings. Then those that know these things the most can comment on any differences.

Here are the pics of the openings. The passenger side is just a plug - it doesn't do anything else.

passenger side

drivers side

 

Your passenger side cover has the PCV valve grommet in place. Your new valve should slip right in unless it's been hogged out by the breather someone stuffed in it. Your driver side is the typical opening for a twist-in oil filler cap.

 

So you think I have the correct covers? It was mentioned earlier that I might have two driver's side covers. It seems like the holes are in the correct place considering how the stock air cleaner would sit "hanging" over the passenger valve cover.

 

I would still reverse it from what is standard for your year.
Put an elbow, or just a filtered cap (is your existing one in the passenger side filtered?) in the passenger side. Put a correct grommet in the driver's side cover and insert a PCV valve into it.
Unless you just can't get there from here (for example, not being able to source a correct grommet), this would be the easiest way, with the fewest new parts to purchase and fit.

If you can fit a PCV valve into the passenger side, that's fine. But you still need some kind of filter for the driver's side. That metal mesh media is NOT a real filter. You need more...

All depends on whether or not the passenger side cap is filtered. Whether or not the air cleaner housing is stock, or aftermarket. And whether or not you can get a grommet for the existing oil fill cap.

Paul

 

That's not a plug, it's a grommet. A "plug" would seal it off and there would not be an open hole in the middle.
It's like an adapter of sorts, that makes the hole smaller to fit different items, and seals the edges to keep dust and moisture out.
Whether or not it's another driver's side cover, would depend on what's under the grommet. If it's just a hole, then it's a legit passenger side. If it's a hole with the two notches for the tangs of the cap, then it's probably a repurposed driver's side cover.
Looks like it could be used either for an elbow, a PCV valve, or an aftermarket filtered cap.

Is it still soft, where you can pull it out? That way we can see the opening.
If it's hard and might be brittle, then don't try it because it might break. Just leave it and see if it will fit the valve.
Got a pic of the underside of the removed cap?

Paul

 

The grommet has the FoMoCo logo in the rectangle on it, so it's the legit grommet. I'd put a PVC valve in it and run a hose to the appropriate vacuum fitting/port as discussed earlier (although I'm not sure if there ever was a consensus as to which port is correct on your application), and put a twist in breather cap in the driver side cover as intended. No sense making this more complicated than it needs to be. This is the one I used when I cleaned up my engine and put on an open air cleaner like you have. It works perfect.
https://www.ebay.com/itm/35448885741...AAAOSwNhJjsMAr

 

Sorry for the confusion - when I said plug I was referring to the chrome cap that sits in that hole. It doesn't have any filter media and doesn't do anything but fill that hole. I can pull the cap again tomorrow and shoot a pic of the underside but it's solid. I'll check the grommet when I pull that plug and see if I can tell which type of hole is there.

 

Would still like to see that pic of the cap, but I would not necessarily try to pull the grommet at this point.
Like 52 Merc said, it looks original and can be used in different ways. Including for the PCV valve. Either way though, changing that cap out for something more appropriate is in the cards at this point.
Merc's suggestion of changing the driver's side to a filtered cap is a good one. Since the part is available and you even have a part number now, it would be a logical and easy decision.
And even though I'd like to see the opening in the valve cover, it's probably just round and I'd rather not see you risk tearing the old rubber up and having to source yet another part!

Paul

 

So I pulled the cap and turned it over - it's not just a plug. I can put a pcv valve in the grommet on the passenger side and run a vacuum hose to the carburetor. It seems like this cap is the type you are suggesting should go on the drivers side cover.

The suggested part is a twist on which I need but it claims on ebay that it doesn't work with my vehicle. If you think it does, I will get it and not worry about what they say.


underside of the passenger cap

this is saying that part doesn't fit my vehicle - will it work anyway?

 

Ebay knows nothing unless someone tells it is so. I would never trust their application chart. I have this same exact EC 564 Motorcraft twist on cap on my 460. The rectangle hold down tang is 1 5/8" long. The gasket has an ID of 1 1/4 and an OD of 1 7/8. I have no doubt your old twist in cap has similar dimensions, and the hole on your cover should be similar. Check it out and let us know what you find. My PCV set up is installed exactly as I described for you above and works fine.

 

I can't argue that about ebay. I ordered the part and stopped to pick up the pcv valve and some vacuum hose locally this afternoon. Hoping to have it put together mid-week if the part arrives on time. I'll post pictures once it's all set.

 

so much for "fast shipping".... i finally got the part and here is the current setup in the attached pic. The PCV fit right in the grommet on the passenger side and the breather cap worked for the driver's side. The only hiccup was the port on the carburetor was smaller than the hose from the pcv. It's not 3/8" so I had another smaller size hose that I put on the male end from the carburetor and then slipped the larger 3/8" hose over it. Do you think that will be a problem? I'm not sure how critical the ID of the hose will be for sufficient air flow.

 

I don’t remember seeing a picture of the back of your engine, but did you ever determine there is a vacuum tree, or additional vacuum port, directly into the manifold?
If there is one, you could connect the brake booster to that and your PCV to the larger port on the back of the carburetor instead of the front.