Blow'in some blue smoke out of the exhaust at startup and oil out of the valve cover breather.

$$$$. You might start with a leak down test,

blue smoke??/is this an o/b?

If youve got oil out of your valve covers and smoke from your exhaust is a sign of a worn engine with to much blow by!On the vacum stroke of a cyclinder there is oil being pulled in and burned,on the combustion stroke,the oil is being burned as well as some of the explosion entering the crank are which in now being pressurized and forcing oil out the valve cover vents!Best do a leak down test to find leak percentage of each cyclinder and youll probably hear air from the valve covers which means the rings are bad,broken,or a wall is scored,maybe a hole in the piston!good luck!

Bingo......

I haven't done a leak down test yet but compression is good on all cylinders. Wouldn't the above problems cause low compression?

Not nessesarily. Oil will create a seal between the rings and the cyl. walls giving you a false cense of a good motor because it will make for higher compression numbers. A leakdown test is best.

Some times Ive added oil to a low comp cylinder just to see if the comp comes up!Its a very prehistoric test but if the comp doesnt come up,its a bad valve,holed piston,if it does come up its a bad ring or two,like,US FOUNTAIN said,oil will seal the cylinders and keep the comp up!

If it is only smoking at startup it could be worn valve stem seals leaking oil into the chamber.......right?

if valve seals leak it will let oil into the chamber and it will smoke at start up but the oil out of valve cover vents is normaly combustion pressure blowing past the ring into the crankshaft area,oil pan,which gets pressurized and pumps the oil out! valves seals are a very common seal to go bad but once the engine is running it isnt as evident,only at start up!