What is C-41B? Good question. I am not sure I know the answer myself.
I just looked at Kodak Z-131 at Kodak's web site. There are C-41, C-41B and C-41RA. C-41B and C-41RA are for minilab processors. I think they are roller transport processors. The Z-131 has tables that show the processing time for each step for each of these 3 processes. I found that:
The development step for all 3 processes are all 3 min 15 seconds. The developer can be LORR or non LORR. They don't matter.
The Bleach step for C-41 is 4:20' - 6:30'; 3:00' - 4:30' for C-41B and 1:00' for C-41RA. The bleach chemicals are different for each.
The Fix step for C-41 is 4:20' - 6:30'; 4:00' - 4:20' for C-41B and 1:30' - 2:00' for C-41RA. The fix chemicals are different for each.
I think I am using C-41B developer (LORR), C-41RA bleach and simple C-41 Fix. These were what they had and I got them that way. I am sticking to the C-41 time for each step anyway no matter what. I process my films in a Jobo ATL-2300. There are no problems except that I need to stick to Kodak's capacity recommendation, not Jobo's capacity numbers.