You can tell if you are burning oil by taking out your sparkplugs--if they are black and mucky then you are burning oil. If they are black and sooty, the timing is off. I had the same problem with my 454 with black smoke coming out of my exhaust. I simply drained the oil and refilled it with the correct amount. (I got overzealous and poured in some Lucas Oil when I had 6 qts in the motor already.) I also replaced the plugs; now it runs much better.