I had to have the driver side cyl head replaced because an injector sleeve wouldn't seal. Had a gm dealer do the work. They installed a brand new head but had to use the valves from the old head. Ever since I got the truck back it caughs out a cloud of oil smoke when I start it. I'm thinking they either forgot an oil seal or damaged one when installing the valves. What do you guys think ? Any work done involving the head has a 1 yr warranty. I questioned the dealer about it but they just say it must be the other head they didn't touch or oil rings. I'm feeling like they just don't want to go back into it. Is there any other things that can cause the oil smoke on start up or should I fight with the dealer ?