Ok, I have an 85 Iroc. 305 carbed, model with a five speed. when I bought it all the computer stuff was unhooked, it ran ok. well the valve guides started going bad so, I changed the heads. The heads I put on had a little bit bigger valves. I dont know if this has anything to do with it but now I cant get the timing mark right. I ve tried switching the pos. of the distributor runs like crap still. tried adjusting the timing chain it was right on. checked the firing order, fine. changed plugs,coils, wires, cap and rotor, nothing. the car runs and drives, smokes a ton of smoke whole car shakes something wicked. Its white smoke but it smells like exhuast. Ive done engines before and never had a problem with this. the closest cylinder i can get to 0 tdc is #5 and thats even off quite a bit. if someone has seen this before and can help me out that would be awsome!!!

 

is it burning oil?

were the heads new? what kind or off what engine? could be leaking oil into the cylinders...fouling the plugs.

 

White smoke is more of an indicator that coolant/ water getting into the cylinders.
Wonder if your timing mark is off on the balancer?
Over time, the outer ring can slip and the timing mark will be off.