Burning oil

[Lated]

My truck is burning oil in the number three cylinder. There is a large cloud of bluish smoke when I start the truck and also if I accelerate hard. My question is this, how can I tell if the oil is getting into the cylinder past a piston ring or dripping past a valve seal. It seems to me that if it was a ring then it wouldn't make a big cloud when it starts because oil doesn't flow up but it could drip down past a leaking valve seal. I'm hoping it's just a valve seal that I can fix when I do my carb and intake manifold swap.