ultranewbieidiot4000

Hi there I blew my head gasket as so many 3 liter owners do. Replaced it, refinished the head. New bolts, and timing belt, put everything together and it smokes giant white clouds out of tail pipe and spits out unburned gas. re sat distributor several times, then took it back apart. Found bad seals on injectors so replaced those, also did valve shim clearance and needed 5 new shims. Friend had said air leak so I cleaned every surface super well and did every bolt to spec. Everything is put back together the way it should be down to the timing marks and vacuum lines..still the same thing any helpful tips? So far ppl say timing, cracked block, or different compression due to one fresh head.