lly no start, lots of white smoke
 

I'm working on my buddies duramax and it has been sitting for a while and now I'm trying to get it going. ive got it turning over fine and trying to get it primed up. its blowing a lot, ALOT of white smoke and acting like its wanting catch an fire up but never does.. the man says it might have a blown head gasket but he isn't sure and I'm not sure the full background on the truck to be able to give a detailed explanation on exactly what happened when it quit. just wondering what to do...ive been priming the hell out of this thing and still wont start. :argh: any ideas? ohh btw its a bone stock(to my knowledge and what I can see) 2005 chevy duramax 2500hd.