Wow man I thought I knew a lot about engines and stuff until the complexity of vacuum came up, I'm clueless in this aspect. The canister I was referring to was a black can, looks like a larger tuna can with two lines going in and out of it, one vacuum and not. That was where the vacuum was weak.

And I don't know what a PCV setup is but I looked it up and don't think I run any setup. I have a oil cap on the left with a place for a hose but the shop I took it to just took the hose off and pointed the place for the tubing down behind my AC box.

Hopefully I'm being some sort of a help, I thought I knew something until vacuum came up, sorry

 

The PCV is a simple, yet important, subsystem. It's function is to suck the gasses out of the crankcase and reburn them. The way it works:

the valve cover, usually passenger side, will have a special one-way valve with a hose that connects to the bottom of the carburetor or the intake manifold. The other valve cover, usually the driver side, will have another hose that connects to the air filter

the theory is that vacuum from the engine cycle will suck through the hose, open the valve, suck gases out of the crankcase. The gases will be replaced by filtered air coming in from the other side

It's important to reburn the gases so they don't accumulate inside the engine and contribute to icky buildup.

 

Not to worry unnecessarily. With a new cam or lifters it's critical to do a cam break-in via a very specific startup procedure. Not doing so can kill a cam in from as little as a half an hour, to as much as maybe 10k miles at the extreme.
Since you didn't change the cam, no worries at the moment. There are other failure modes of course, but we'll tackle them if we run across them.

Hah! You should see under the hood of a '79! Well, at least when it was all intact. Most of them have been stripped of anything that reminds people of smog equipment. Which is unfortunate sometimes.
Your '74 would have had far fewer vacuum lines and fittings and oddball thingies to contend with.

And to add to the mystery, most every vehicle had multiple variations based on engine model, year of vehicle, state of original delivery, GVWR rating and probably several other things.
It was a relief when they finally started getting their knowledge base compiled and everyone could get on the same page with the emissions stuff. At one point most vehicles finally came with a minimal variation on the same theme. With mostly those over 8500 GVWR getting some breaks for a few more years.
But that was a good learning curve. Look what we've ended up with these days with the modern vehicles! What comes in a Honda Civic would have seemed like NASA black magic and voodoo all rolled into one. And a streetable muscle car with 600 hp that was easy to drive on pump gas and got 30 mph would have been laughed at in the '70's as science fiction.

Ok, that's an additional vacuum reservoir so that under conditions of low vacuum, such as when you floor it or are heading up a long steep hill where your gas pedal is pushed hard, anything that requires vacuum to function will have full vacuum for at least a little bit.
Not sure if weak vacuum is a sign of something bad or not in this case. Maybe someone's checked more recently than me and can tell us both. But I believe that the hose that supplies the vacuum to the can has several impediments/valves in it's way. So a weak vacuum signal could be totally normal.

I hate it when a shop leads someone down that path. You'd think they'd have learned 30 years ago that PCV systems are "good" smog equipment that does not rob one iota of street performance (race engines are a different story most likely) and helps us achieve such good mileage and oil change intervals as we have today. All can be credited to the lowly PCV system.
As PapaBear said. It's good to have and you should re-introduce it to your engine. You might have to re-adjust the carb settings afterward, but it's totally worth it.

But then again, that's why we're here in the first place. Right? To lean something. I do and I've been fiddling with these stupid things for over 40 years!

We'll get yours out of it's funk. Hang in there.

Paul

 

So could a PCV system not being there be causing this problem? Seems to have ran fine before missing the PCV system before this problem. Alos if it helps my driver side oil cap has a vent on the bottom and I can see smoke coming out of it, is that the gases that should be reburnt? What's the difference if they come out of that vent or are reburnt? This is all so new to me, but from my understanding I don't NEED a PCV system but should, will it effect anything? Ill check for vacuum leaks tonight or tomorrow.. THANKS

 

The PVC system is a must unless you're running a downdraft tube (old style crank ventilation) or a bung welded into the header collectors and straight pipes. PCV...positive crankcase ventilation...system allows the innards of the engine to "exhale"....or breathe better. The equilibrium of air pressure is such that you get no "blow by" at the oil filler tube, rings or at the dipstick.

The difference between unburnt oily gasses coming out of the valve cover vent or introducing those gasses to the intake via vacuum is one of a messy situation (venting the gasses through internal engine pressure) and positive ventilation (PVC) creating equilibrium in air pressure in the engine's guts.

 

Not having a functional one where there was one before can/will change the overall air/fuel ratio if the carb was jetted for use with the PCV in the first place.
Add that to possibly other vacuum leaks or something else that's changed, and yes the missing PCV could have an effect. It's mostly a long term thing, but you never know.
Maybe it's not a big deal, or maybe it is. Every engine combination is a little different, so different things act differently. Just to be different...
So you don't know what you don't know. You know?

Paul

 

Most of your issues don't sound PCV related, but you might as well fix everything that you come across that's not quite right, so that it doesn't skew your results when you start hitting on the actual problems.

Heck, some of your stuff could actually be ignition related even. A weak spark causes all sorts of trouble. Weaker vacuum, popping and coughing. All manner of ills.

Remember, if you can't fix it with a hammer, you have an electrical problem...

Paul

 

Definitely check your vacuum advance servo and make sure it holds a vacuum and moves the breaker plate.
You can pull the vacuum advance hose from the carb and suck on it with your mouth, with the engine idling, and you should be able to hear the idle change, or possibly see a difference on a tach.

Maybe someone adjusted the carb for a smaller vacuum leak - and the leak got larger on you.
Or you might need to rebuild the carb, which isn't too difficult at all really.

Engine pics might shed some more info too...

 

PCV introduced in 1961, but not all vehicles came with PCV until 1966.

1968/76 F100/350 360/390; 1969/79 F100 302; 1975/79 F150 302:

Right (passenger side) valve cover at the rear has a hole in it. Rubber grommet fits into hole, smog valve fits into grommet.

Smog hose routes from valve to nipple on rear of carb or to nipple on carb spacer plate.
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Left (drivers side) valve cover has a hole in it at the front. Oil cap w/hole in it fits into valve cover, rubber grommet fits into hole of oil cap.

90 degree plastic elbow fits into grommet. Smog hose routes from elbow to nipple on the air cleaner.

 

I do know that before this when it was in the shop for almost the same thing, it was a condenser and the guy before bought crap china parts including Distributor, coil, plug wires, and plugs. I think I'm gonna take it to that shop who took out my PCV and ask them to put it back, and check electrical and I will replace the plugs.... Any other advice? Thank you guys so much!