As long as overall development of child is normal like running,playing,walking ,this excessive drooling
can be taken as normal.
Many children drool excessively during teething
and this drool stops once teething stops.
On the other hand excess saliva has many advantages like it keeps teeth clean,helps in protection of oesophagus and intestine and also helps in breaking down of carbohydrates.
Consult a pediatrician
and if he is satisfied with the overall growth of the child,you can relax and wait till teething process is over.