RockinRam96
Active member
- Joined
- Sep 15, 2011
- Messages
- 2,702
What's the difference between the 4MG and the 7FB?
I believe the 7FB was the fist 3406B serial numbers, most of which had a water jacket charge air cooler, rated at a max of 400 hp in a road application. A few later 7FB's went to air to air, which were the first 3406 rated at 425 hp. The 7FB also has a different cam shaft in the pump that has more timing built into it than the 4MG or 3ZJ (3ZJ is the first 3406C SN).
My father had a 7FB in his 379 that he said ran like a raped ape. He now has a 350 hp 4MG in his puller that is a very strong runner, as well as a 425 hp 3ZJ in his work truck that put 500 hp to the ground with stock CAT parts.