Handyvan 3cyl get smoke everytime start the car

hi...can someone help me to fix the problem
i got the handivan 659cc 95 EF model. Everytime start the car i get a lot of blue and white smoke out of the exhaust but after 5-10 seconds it return to normal.
i had change the stem vale seals but still no good
then i changed the piston rings and send the head away to the ''cylinder Head specialist'' for a fully services.
i checked and blowed all the oil line and top cover before i reassembly.
After all...i still get the same problem with the smoke.
anybody know what i suppose to do to fix this problem

thanks

If I lived in a flat city then yes.

However, where I live there are many steep hills I need to drive up. My 1.6L corolla only just makes it so I wouldn't want anything less.