I am trying to detail my Maquette 1/72 DB-3 kit, and read online that the DB-3 was equipped with the Nazarov M-87 9 cylinder engine.
You have got some unreliable information....
Engine designations didn't include designer's name. There was no such thing as Nazarov M-87 or Tumanski M-87. There was only one M-87 14 cylinder engine which was developed from the French Gnom-Rhone 14 engine.
Designation DB-3M is dubious; it appears in Shavrov's book published in 1970es. In more recent literature (Kotelnikov) it is explained that designation DB-3M was initially (and very shortly) used for DB-3F (later re-designated as Il-4). If you are modeling a DB-3 which was made in 1939, which had M-87 engines and larger pilot's canopy, that version was designated as "
DB-3B" or "
DB-3 Modernization B" or "
DB-3 model 1939"
HTH,
KL