Found this bit of paper at work and i thought i would post it up. Found it in with some very old fan belts.

The number of fan belts for the 4M engine has been increased from one to two. Production effective from engine No.

4M-0197032. (July, 1977)
M-U, M-J 1177297.
M-EU 1175186.

When replacing the fan belts, Make sure to replace the two belts as a set, If one belt is replaced, The durability of the belt will be decreased.

Des