I had a problem with my 56 324 Olds Rocket that a friend told me a fix for and it worked, thought I would share it since it came from an "Old Timer" that knows his stuff. The thing would smoke like hell if you punched it to get on the freeway. Same for going up a hill, it would smoke like hell and then clear up after you hit the flats. I'm pretty sure the thing has never been touched for a rebuild so I checked compression and did a leak down, everything was within reason for an old stock engine! So I'm bitchin about it to my buddy, and he says he had an old Y block Ford that did the same thing and he couldnt figure out what was going on until an old mechanic told him to check his rear oil return passages on the heads. Sure nough they were clogged, he cleaned em out, problem solved. If you accelerate, or go up a hill and the rear passages are clogged the oil builds up under the valve covers and if the guides are worn it sucks the oil right down. I just got done doing the same thing on the Olds. I pulled the rocker assembly while I was at it and the manifold, valley cover etc. The rear oil returns on both sides of the motor were amost packed solid with gunk. The main cause was the stem seals had turned to hard plastic and a couple of chunks had broke loose to end up in the passages. I had some stainless multi-strand wire in the shop so I cut some and put it in my drill to do the roto-rooter method, along with some solvent and an occasional blast from the air hose until the passages were clear, (be sure to put a rag on the lifter side to catch any chunks). I soaked the rocker assemblies and cleaned them both up, pulled the push-rods and lifters out for a dip in the tank and inspection, (make sure they go back in the same holes) You can take the lifters apart, but I elected to just clean them and try them out first. New stem seals, some gaskets and the thing is doing great. I still have just a bit of smoke, but I ran a pretty strong mix of Sea Foam in the tank to help clean things out some more, so I'm hoping that will go away once I put a full tank of just gas in. Hoping to enjoy the car for the summer and maybe do a full rebuild next winter. It's a quick fix if you stay on it, but took me a couple of months of a half hour at a time on it here and there, between other projects...like my wife! Hey, have fun and I hope this helps someone out!
Good info ... The breather filter canister on the road draft tube used on some '40s-'50 GM cars is another item to check - plugged solid on many cars that never saw highway use.
Oh yea, forgot to mention that one. My filler breather canister was rock solid, the originals were filled with some kind of fiber, mine looked like horse hair, I started to clean it out and it fell apart. I went for the quick fix and cleaned all the grease and fiber out of it, (real bitch to do since it is not made to come apart, so you gotta work through the holes) then looked for something that would replace the stuff, green scotch-brite pad cut into about 2" squares and stuffed in until it seemed full, but not restricted, has worked so far. I oiled it a bit to make the dust stick to it. The good thing about the pads are that they are oil and solvent resistant, and if you get the scotch brand, they don't start to break down, at least not right away, I'm watching mine. Heat, at least in this application, is not a problem. Steel wool might work as well, my concern would be little strands getting sucked into the engine.
My 55 olds had the same problem. I got 3 of the 4 holes unplugged, (finally), still have a rear one plugged. Good info on the breater.
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