Most of the time, when you rebuild a non turbo 300d, you will find that the bores are out of round. The only way to make one stop smoking is to have the block sleeved and install new rings.
We order the sleeves and install them with our press and special installer and then have NAPA machine shop deck the top surface.
This has worked for us many times in the past.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS