My F150 1979 351m runs great, no knocking sounds, no smoking except first thing in the day (probably worn out valve steam seals) and 21/22 steady manifold vacuum at idle (very slight vibration of the gauge needle), good oil pressure. Starts right up, no hesitation and decent power. However...
1. Found milky foam on the dipstick, sometimes all the way to the top of the dipstick. Changed the oil (looked fine except perhaps thin and a bit of fuel smell?) and my oil pressure when from the middle of NORMAL to the top of NORMAL, after a couple of days driving the pressure went back to the middle of NORMAL and I found the whitish foamy stuff in my dipstick again (condensation or water?).
2. Since I got the truck this year it blows smoke out the passenger side breather connection, which is currently not connected to the air filter ( thought there should be negative pressure there, not positive since the PVC valve is creating vacuum or negative pressure on the driver side). The PVC valve on the driver side valve cover seems to be ok and is connected to the carburetor.
Again, the truck is running fine but I am worried that I might have a ticking bomb issue. Any thoughts?

 

Ugh, those do sound like a bunch of head gasket symptoms...

 

Since your vacuum is steady I would diagnose a head gasket issue that is currently only affecting the sealing of the water jacket, next will be compression... tick, tick, tick, BOOM! I would fix it ASAP

 

Looks like it's time to pull the heads I just put it back together after replacing worn lifters and a couple of bent push rods. I will need to take the intake manifold out again right?

 

Yip. the reason why I diagnose your issue to be water jacket seepage is due to your vacuum remaining steady. What color is the smoke? White is typically water and black is typically oil. Do you have true dual exhaust? If so you may at least be able to tell which head it is.

 

Unfortunately it looks like it had dual exhaust but they joined into one half way and then divided it into to at the tail. Smoke is white/grey. I did a quick dry compression test and it wasn't great as I recall, specially cyl 4. The oil I replaced looked good, except that it shows the milky stuff on the dipstick and the oil pressure decreases a few days after changing the oil.
Would the fact that it blows some smoke up the breather be related? or is that some other issue?

 

That is most likely, as you stated, valve stem seals. A little smoke coming from the breather is typical. Blowing from the breather typically means compression bypass via stem seals etc. Oil will turn gaseous under normal operating temperatures especially in your head galleys but it should be just easing out not blowing. Also when smoke is coming out your breather it typically means your oil separator medium is saturated and needs to be cleaned.

 

My 352 had about the same problem. Milky stuff on dips tick & inside breather cap but not in the oil and thus was only in colder weather. Turns out it was condensation from too many short trips & not letting the engine get hot enough.

 

I concur about the condensation and short run time issue.

Second, get your PVC system in order. It can be either an open or closed system. An open system will have the driver side has a breath cap open to the atmosphere. A closed system will have the cap connected to the outside of the air cleaner housing with a prefilter. On the passenger side on an open or closed system is the PCV valve. The PCV valve has a hose connected to the clean side of the air filter or directly connected to a spacer plate under the carb. Engine vacuum opens the PCV to draw crankcase gases into the combustion cycle to be burned as part of the intake charge.

 

I am hoping that's what is wrong. I do only use it for short 3-mile trips right now and the weather is pretty cold. Today I found a lot of the foamy stuff under the oil cap and the breather connector but none on the dipstick.

My PCV is connected as follows:

Driver side: PCV valve connected to base of carburetor



Driver side PCV to bottom of carburetor

Passenger side: Currently not connected to anything, I am assuming it just connects to the air cleaner. I believe there should be negative pressure here so that it sucks air in? Instead it blows smoke out.





Passenger side. Connecto to air cleaner?

 

Your truck is set up as a "Chevy" where the PCV is on the driver's side. No matter, it can work that way too. But I suggest configuring it as I described above because the truck is a Ford and would lead to less confusion

The main issue I see is that your PCV has two ports and one is open. That open port needs to be plugged because all the carb us sucking is air through the open port. The carb's vacuum is probably not opening the PCV valve to actually evacuate the crankcase gases. That means you have a lil zone where warm and cold air linger and the difference is forming condensation.

Second, get an open element cap or a breather cap with an elbow to connect it to the air cleaner housing.

Btw, is your air cleaner housing an enclosed (OEM) version or an open-element??

Here is diagram for guidance.:

 

Thank you for the help. So I should just plug the top port on the PCV valve?
I have both the OEM and an open edelbrock air cleaner. I have been using the open element because the smog stuff was half way removed, so I removed the rest of it and just kept the vacuum lines for brakes, tranny, advance, PCV and heater controls. Is there an advantage to using the OEM air cleaner instead of the edelbrock? Obviously I am not using the chimney or any other artifacts on the air cleaner, there is a bunch of vacuum ports on the original air cleaner which I would not know where to connect.

 

That PCV setup is the correct factory orientation for your truck. Ford has done it both ways over the years depending on the model and engine. I agree it looks like the top port on the valve is open - normally a replacement valve comes with a plug in that port that can be removed if needed. A simple vacuum cap will suffice. The passenger side hose normally would connect to the PCV filter inside the OE air cleaner to supply filtered air. You could substitute a push-in style breather, but I would just go back to using the OE air cleaner.

Condensation on the dipstick and oil cap is common if short trips are made in cold climates. Plugging that vacuum port so full vacuum is applied to the PCV circuit will probably help with the condensation issue and might even reduce the blow-by you are seeing. If you are still getting blow-by then its an indication that your rings and/or valve guides are worn.

 

I've spent the last 2.5 hours combing thru 3 manuals, and doing internet searches looking for an answer to my question: what does this hose do?
Correct me of I'm wrong, but your post answers it 100%, yes?

Truck was having idling issues yesterday. Popped the hood when I got home and found the hose disconnected at the air cleaner. Is this the right type of hose? It also looks a little short and is extremely hard to fully connect to the air cleaner housing.

 

Yes... Yes it does... read post #12 above.