Dammit...you're gonna make me come down there yet, aren't you? Okay...Okay, don't panic (yet!). Start with a compression test. This will tell the tale quickly. If the two suspect cylinders read low, then try a shot of oil into those two cylinders and re-check it. If your reading goes up noticeably, it's a ring problem. If not, likely valve guides. Were the heads rebuilt along with the short block? Since it is both rear cylinders, a leaking intake manifold gasket COULD be the culprit...allowing engine vacuum to pull oil in from the lifter galley. Pull the valve covers and take a look at the springs on the bum cylinders. Are the valve seals in place? Do these basic preliminary steps before you do anything drastic like dropping a small Chevy in there! Let us know what ya find!
what kind of vavle covers you have? are they baffled? i would check the pvc system, might be sucking oil.
Oil inside of the hose for the PCV system would indicate a problem...but if the PCV were pulling oil into the intake, I'd expect it would foul more than just the back two cylinders. A PCV system needs to have the valve located in the intake or a valve cover with a vacuum hose run to the intake or carb, and it also needs a vented cap or breather elsewhere...either as in an oil fill tube, or on the other valve cover. This allows the crankcase to 'breathe'...the PCV valve will allow engine vacuum to pull crankcase vapors out of the engine with the vent or breather serving as the entry point for fresh air.
Start simple...go with the new cap first...make sure it "breathes". Also, as Ricky stated, you will want baffles in the valve covers help keep oil out of the PCV system.
Actually, oil coming through the PCV setup makes sense. If it's a sizable amount of oil it wouldn't mix with the gas & air, instead puddling in the intake manifold and running downhill towards the rear cylinders...
my 302 is just like that one, hell, I think we have the same valve covers (ford motorsports?)! I have a little of the oil problem myself, but i'm not fouling plugs. There's definitly oil in the pvc and breather though. My big problem is that it falls on it's face when I floor it, like when i'm trying to pass a slow-ass doing 20mph under the limit. It doesn't really bog, it just won't accelerate until I let out of the gas some... then it takes off. This is a holley 600, vacuum secondaries. All new vacuum hoses, so I don't think it's a leak, not unless it's at the base of the carb...
I find it hard to believe that chrome breather doesnt do the job did you check the pcv valve if it rattles to easily the spring inside might be worn out. while your at the store put a k&n[tm] on your engine you will notice a difference on a stock engine and especially yours with a 4 barrel.
VonT, it's performing really well. It's a Holly 600 on a Eldy intake, and some unknown somewhat lumpy cam, running through some beat-ass headers. It never runs rich... if anything, it's maybe lean. It's got a MSD 6A box, but i'm running platnum plugs, which is supposed to be a no-no. The only problems i'm having is a bit of dieseling when it's been running a while. I'm gonna change to some autolite plugs, and that should fix that... I'll check it this weekend for some vacuum leaks at the base..
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