Keith,
You've probably blown an
Intake Manifold Gasket. Due to the design of the FE engine, the head/intake manifold mating surface is inside the valve cover.
Oil that is pumped up to the rocker shafts (and there is a lot of it) drains back into the lifter gallery right across some of the head/intake mating surfaces. If the intake gasket fails, vacuum in the intake manifold can suck
oil into the passage and result in a lot of smoke from one side of the engine. I think this is especially common on aluminum heads that have not been periodically re-torqued. A good quality gasket is also manditory.
The good news is it's not an expensive fix.
Steve