I put a Walbro 340 in yesterday and had to charge the battery all night. Anyways, When I start it, it fires up real choppy with gasey smelling smoke coming out the tailpipes and driver's side breather. When I give it gas it tries to die, rpms drop, and black smoke comes out the tailpipes. (I also put a new coilpack and plug wires on it.) I took the top off the coolant resiviour and find just a few small bubbles coming up every once in awhile. Also, when I shut it off and took the pressure off the radiator cap it sounded like it was going to boil over. Is this a blown head gasket/ motor and if ti's the gasket, what is the average cost to have a mechanic fix it?