On the magnum series engine, including the 3.9, the intake is two pieces, but, the bottom piece is a flat plate that seals the bottom of the intake. If that gasket gets blown out, it has a direct path to the crank case... hence, it sucks in oil. My old 5.9 would go thru a quart of oil in 100 miles.... fixed the plenum, and it was a now a quart between changes....

 

That makes sense @Hey You .... I think I read above they went through 1 quart of oil in 20 miles.
I never claim to be a mechanic and just fumble through this stuff myself ... I have never worked on the Magnum engine.
The only thing I can think of with that much oil usage is in the intake area and a bad gasket. Oil literally getting sucked out of the crankcase.

I know some GM vehicles used a plastic intake manifold that got old and cracked. I do not know if the Magnum has any issues where the intake needs to be replaced ....
So bad gaskets is all I can think of.

So I'm thinking this is a fairly easy fix .... a lot easier then swapping in a used engine. It just makes sense to me to fix it.
With 218K miles on existing engine, is hard to say how long it last .... they say it runs good .... possible it may make it to 300K miles? Maybe only 250K.
For $100 in gaskets I would have to fix it.

As far as used engines .... car part.com in my area shows several 5.2 engines between 125K-135K miles for a price of $500-$650.
So $800 on Ebay is pretty high plus you have to pay shipping for it. car part.com using your zip code you can find one local you can go pick up.
So you fix your current engine and drive it til it dies .... in the meantime you window shop and pick up a used engine for it. Dont wait til the truck dies and cant go pick it up.
Pick a time on your schedule to change it .... plan and prepare for it.

The bad news is, you will get another 25K-50K miles out of existing engine .... then you're going to install another engine for another 150K miles ..... you need to start maintaining your truck. Change the rear end oil, grease the u-joints, service the brakes and suspension .... clean the interior .... it is no longer a throw away truck.

 

And, with all of that, it's cheaper than a new truck payment!!!

 

I changed the plenum because it was burning oil before probably 1 quart every 50 to 100 miles

 

I’ve also read it could be the pcv valve? Won’t that cause vaccum issues as well? I completely forgot but when i run any higher than 2k rpm my ac vents like will change to the floor or the windshield or when I’m on cruise control at 65 they run fine but if Im going up a decent hill then they will switch again

 

OMG .... I SHOULD SHUT UP NOW!
But I wont. ..... I'm trying to look at the gasket surface and see where it might leak to cause your issue. ..... On the passenger side near the rear it is wet and maybe was your issue.

The bigger issue is all the filth on the engine. If you bump that distributor cap a shovel full of dirt will drop into the engine .... we can see evidence of where it has already.
The gasket surface is incredibly dirty ..... In order to get it spotless for a new gasket to seal ... all that crud is going into the engine ..... it will be a terrible painstaking process to get all the crud out of that engine and clean gasket surface to make the new gaskets seal.

Very first thing that should have been done is pressure wash and clean that engine before you opened it up .... now it is too late.
I honestly can not remember the last time I saw such a filthy engine and it still runs. ..... you get bonus points for that.

I'm not a Debbie downer or something ..... That engine has been rode hard and never saw any maintenance .... be happy you got 200K+ miles from it.
You say it actually runs now? .... go grab another engine while the truck still runs .....

There is a lot of natural sludge in the engine to be expected. But introducing all the extra dirt into it .... it is in the oil and going through all the bearings .... that engine will not run long.

It reminds me of a DR opening up a stage 3 cancer patient and wants to do some work .... Once opened they realize it is a stage 5 cancer and they just close the patient back up because they are beyond their help. Nothing they can do to fix it. IMHO thats your engine right now. .... I would concentrate on replacing the engine.

I would not try to repair this engine after seeing the photos .... others may disagree and thats fine .....
The obvious lack of maintenance, the fact it survived 200K+ miles ..... praise it and put it to bed.

 

lmao I cleaned it it’s beautiful now, but I diddnt pay anything for this pickup but yes it’s been a farm truck and they never changed the oil I’ve also cleaned out the oil pan and entire crankcase it was horable

 

Ok thats cool and you impress me .... judging from your past post I was not sure you were willing to put in the effort needed.

I still think you have a leak of some sorts that is allowing oil and coolant to get sucked into the intake ports and burned ..... maybe it is a cracked manifold?
Could be you have a opportunity to do a better job cleaning and installing new gaskets. ..... somewhere you are sucking oil into the cylinders and the intake is the most obvious place of origin.

I have no idea where the original issue is coming from or whats causing it ... cracked manifold, broken part, warped manifold ... bad gaskets .... something is not sealing.

Same time I wonder how much time you want to spend on a old farm truck engine that never got any maintenance or oil changes .... it is your call.
I just imagine new gaskets, maybe a used intake .... the time you already spent on it .... $500-$600 you can get a engine that got some sort of maintenance and is warrantied for 90 days.

I bet you have $200 into it now and no improvement ..... that engine you have is done, stick a fork n it .... call out the fat lady to sing .... smile and move on.
Life is too short to waste time on impossible projects.

 

lmao I’m gonna try a pcv valve and see if that helps u don’t think it’ll solve it completly but if it will help I plan to rebuild a 413 crysler this next year lmao

 

Have a look here. See that plate on the bottom? Gasket for that is the problem.