rebuilt 2.3L oil issue

:banghead: I recently purchased a 93 Achieva for $300. It needed engine. I put in new crank, pistons, rod and main bearings, rings, timing chain, oil pump, and all gaskets and seals. This aint my first engine job, so I pretty much know how to do it. Motor had lifter tap for the first 100 miles or so but oil level and pressure were fine. It has had white smoke from exhaust since I fired it up. It ran fine for fist 1000 miles, but then oil pressure dropped so I checked oil and it was mixed with gas. I changed oil but now it won't maintain oil pressure. It starts at 40psi but drops to 0 in about 10 minutes of idling. Thought it was oil pump issue so I replaced oil pump and checked all bearings for clearance and torque and everything is within specs. When I change oil it gets as thin as water in about 10 minutes or so, causing oil pressure to drop. I even tried putting 2 quarts of Lucas stabilizer, and topping it off with 15w40 oil and that only lasted bout 15 minutes before it got thin as water. I've checked compression to see if rings were blown but it hold 180psi in every cylinder. Anyone have any ideas? Every mechanic in town here is stumped.

is there oil in the coolant?

No oil in coolant and no coolant in oil. Doesn't overheat. Barely gets warm before oil thins out.

are you saying the oil is mixing with the gas? if so that is quite the quandry.