Auto Parts: oil leak + blue smoke exhuast, head gasket, valve seals

Question
I had a head gasket repaired and on inspection about 2 weeks later i was down 2 pts. of oil never has my northstar 4.6 leaked oil then I noticed blue smoke coming from the exhaust on acceleration shouldn't the rings been replace when the engine was apart? I suspect poor service and mechanics knowledge about Cadillacs.

Please Respond Thanks
Anthony

Answer
    This is a tough one.  No, they wouldn't have replaced the rings while servicing the head gaskets.  Replacing the rings requires disassembling the bottom end of the motor as well as the top, basically completely rebuilding the engine.  There are only two ways that oil could get into the cylinders on a Northstar: bypassing worn rings, but if you didn't have this problem before it wouldn't have happened suddenly, or the valve seals in the head leaking (there are oil passages in the head gasket that permit oil to get up to the valve train, but a new head gasket should have sealed them, and they'd probably leak to the outside, not into a cylinder).  I am assuming that you are familiar with the white smoke you were getting as the engine burned coolant from the leaking head gasket, and that this smoke is significantly darker, but not black like soot.  If so, it is almost certainly oil smoke.  As to the 2pts of oil that were missing, could they have been missing from the time you got the car back?  In other words, was this the first time you yourself had checked the oil after the repair?  If so, I wouldn't assume that it was full to the line after the repair.  Two pints is only half of a quart in an engine that holds a lot of oil; they may have just put in an even number of quarts and been satisfied when the level fell between the add and fill marks on the stick.  If you did check it right after you got it back and it has used half a quart in two weeks, then something's wrong.  Did they just do one head gasket?  I know that's cheaper than doing both, but not much cheaper since most of the same stuff has to come off to do one as two.  These engines are different from most American car engines, but anyone who is accustomed to working on Japanese and European cars wouldn't find anything strange about them.  I really think you ought to drive it a little while longer, maybe a couple of more weeks, to see if this trend continues.  However, I'd let the mechanic know about it right now.  If he's a good mechanic and stands behind his work (if he doesn't then you shouldn't be patronizing his shop) he will probably want to look at the car and see what is going on with it.  Good luck.