I posted earlier about this problem, 82 F-250 4X4 with 400M , uses quart of oil in 300 miles, with no signs of it. I did a compression check 150 to 160 lbs in each cylinder, vacuum check to check the valve guides, 18 lbs and a steady needle, PCV system IS working properly. No leaks. I assumed it was the valve stem seals as it smoked on start up but quit immediatly. So I replaced the stem seals, changed the oil and started over, still uses a quart to 300 miles!!! And now it dosen't smoke on start up even. Wouldn't it smoke badly if an oil ring was broken? My spark plugs aren't oil soaked or fouled. I'm lost!! The truck runs great too. HELP!! I've thought about the intake gasket as its the big metal pan deal, and its the original as the truck now only has 88.K on it. ( Original miles ) maybe its rusted through inside the lifter valley and its sucking oil internally on the intake. Has anyone ever experienced this?

 

It's good to wonder about the valley pan,but I don't think rust would be a factor,unless the bolts were ever loose and allowed some coolant seepage which eventually ate into the sheet metal at critical areas like the intake ports.You mentioned the PCV is working correctly, but where is it located(valve cover,oil cap,intake,etc.)? What if the EGR spacer plate gasket has a tear internally? Is the plate blocked up with carbon/sludge? If all of this checks out,I don't know?
Phillip

 

Phillip, I forgot to mention the truck has sat mostly for the last 8 years, I didn't know if it may have had alot of condensation buildup & maybe the moisture got to it , or acidic old oil from it setting so much. The 351M & 400M have also what is called a dry intake they have know water passing through them. The PCV valve is located in the valve cover on pass side which pulls its vacuum from the carb, it draws through the opposite valve cover through the oil breather cap then on to the crankcase breather filter located in the air breather, and it is all flowing good. I hate to give up on this motor as it runs great!

 

Over 8 years idle time,even a little running,you will have some varnished rings that are stuck to the piston.Get you about 2 cans of liquid B-12 Chemtool by Berryman,pull the plugs,and pour enough into each cylinder with a trans funnel to totally soak the cylinders, at least over night.Every hour or so, top off by pouring a little more in.In the morning,crank the motor over several times to throw out what liquid that may be left over.Make sure it all comes out before you put the plugs back in.Check your oil level to make sure it didn't overfill,some B-12 is safe in the cranksafe.Get the motor started and let it got hot before you take it out to accelerate hard on it several times. Your compression should rise to about 165-170 if the douche helped.
Phillip

 

You don't have aftermarket valve covers that lack a baffle do you? I had a 302 suck a whole bunch of oil out the pcv and into the intake untill I replaced with baffled covers. Just a thought.
good luck

 

BigBrownTruck, no it has the stock valve covers on it, the PCV valve system was one of the first things I checked, I'm going to try Philip's suggestion, that was one of the things I'd been thinking about also, either a broken or stuck oil ring, I went back and re read my post I left the stuck ring part out. Its hard to think of all the things and them make sure you got it all on here, I would have thought it would smoke though with either, but at this point I'm going to give it a whirl this weekend as I don't have much to lose.