could be a number of things
are the mixture screws set anywhere near right ? you dont want them tight in or fully out
is there a plastic type insulater block between the manifold and carp ? make sure its the right way around as that can cause problems
it might not even be the parts you changed it could be ignition fault, make sure the dist is conected propely, pull 1 of the ht leads see if you get a spark
its probally 1 of thoses little faults that is so easy to overlook
good luck