The 3406B injection pump is basically the same from 310HP all the way up to 425HP. The difference is the static timing on the cam. It is engraved on the end where the timing advance goes. Timing has lowered through the years for emissions reasons. The early 3406's had 26 to 28 degree timing. Along about 1987-88 timing dropped to 18 to 24 degrees, and finally the last 3406B's had 14-16 degrees. Look for the serial number on the block of the engine. It should be either 7FB or 4MG prefix. Most 7FB's had 24-28 degrees while most 4MG's had 16-22 degree timing. As far as the governor and barrels and plungers, they are the same on all applications.

Around 1991 Cat changed the injection pumps and went to bigger cam bearings and plungers. This can be noticed by 7E-5888 cast in the housing, while 3406B pumps had 7W-3906 cast in the pump. Timing also dropped to 9.5-11 degrees on the later pumps.

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