1986 F150 300 6cyl auto (C6?) 2WD

Been doing this since I bought the truck, basically oil is sometimes coming out the breather hose connected to the front of the valve cover and going to the air filter assembly.
When I replaced valve cover gasket I noticed it has a baffle inside to stop oil from going into this hose so why/how can it do this?
And it can be a lot of oil sometimes like a 1/2 qt ruining my air filter as well.
Thought maybe PCV valve wasn't working but when I take PCV valve out and place finger next to hole it has suction but I dont hear the PCV valve doing anything when it's in the valve cover?
The truck NEVER smokes, doesn't burn oil, etc so I have no idea what could be causing this?
Another thing is whenever I take off the gas cap there is a whoosh of air like it's under pressure...could this be related?
Thanks for any help!

 

It sounds like you have a sticking (or worn out) piston rings. Your getting a lot of "blow by" which is causing oil to by pushed out of valve cover breather hose. Until you fix the problem, you may want to extend the breather hose and just let it hang somewhere to let oil drop to ground.
I would start by taking a compression test and doing a cylinder leak down test. You might be able to free up a sticking ring with some of the over the counter products. If it is a ring (say you have a cylinder with a lot of leakage), you could remove the spark plug a pour some cleaner in the cylinder than let it sit for a while to unstick the rings and then crank the engine over to spit it out. After that change the oil and maybe go to a 20W50 weight oil.

The air movement (Swoosh) at your gas cap is air entering the gas tank. The tank/fuel-system is "sealed" so gas vapors don't escape. Vapors are drawn into the charcoal/carbon canister locate din the engine compartment. As the gas level in the tank drops there is a slight vacuum created in the tank, so when you remove the cap you hear air rushing in.

 

Thanks bro!
But actually the air is shooting out of the tank when I open it, not sucking in?
Dang the engines so quiet and runs pretty good no tapping or anything but I guess maybe it's worn out some?

 

Yes, it's worn some, but as long as it doesn't foul the plugs it will run a long time like that and has lots of life left in it.

I have hooked a hose to the breather line and run it down the frame also, just so it doesn't over whelm the carb with all the oil and smoke, but I was flamed a little bit by some motorcycle guys who do not like oil on the roadway. So a easy solution to that would be to hang a small catch can somewhere low and put the hose in that.

For your fuel tank pressure problem, you must have a blockage in your tank breather line. The tank(s) have a small plastic roll-over valve in the top, with a small line that runs over to the pass side of the frame. This line runs all the way up front and hooks into the charcoal canister in the engine compartment. This is what lets the tank breath with the cap on it.

Check for this line. It may be plugged off if lots of lines are missing in under the hood.

 

A cylinder leak test is the best way to check. The way it works is you thread the hose into the spark plug opening and with the cylinder (piston) rotated so that the exhaust and intake valves are closed, you inject steady air into the cylinder (from shop air compressor). If the valves are leaking air you can hear the air coming out the intake manifold or exhaust pipe. If the rings are leaking you will hear the air coming out of the crankcase (valve cover). This is a good way to pin point the problem. If you don't have an air compressor or a cylinder leak down tester it would be worth it bring the truck into a local shop and have them do this test.

Regarding the gas tank swoosh. Are you sure you have air coming out and not going into the tank? if it is rushing into the tank you may want to replace the gas cap. There is a vent/valve in the cap that may be stuck causing excessive vacuum to build up in the tank.

If it really is coming out of the tank - then my only explanation/guess would be this: on fuel injected trucks, fuel is pumped out of the tank to the fuel pressure regulator and fuel manifold. Some of the fuel is then returned to the tank. So pump is removing fuel from the tank and tank level is dropping (and space fuel was in is now replaced by air) then the returning fuel is possibly creating a positive pressure in the tank because the air in the tank can't get out fast enough (??). However, my first step would still be to replace the fuel cap (not with a universal cap that fits all - but with a proper Ford cap).

EDIT: Franklin was posting as I typed. I forgot about the breather tube. So check that and the fuel cap.