I don't know about the C-7 but the C-12 and C-15 are both basically 3406,s with modern electronic control. The C-7 aperies to have come from the earlier 3126 series engines which were both 100% CAT. I have always been a big fan of CAT I just like the way that they drive almost any transmission seems to shift better behind a CAT with their smooth power curve. I do however have to agree with Matt above it is hard to beat the old Cummins Big Cams just because they worked well and are so cheep and easy to in frame. I don’t know anything about the new electronic Cummins motors though.
As far as the rest of the CAT C660 trucks I am stuck on Kenworth’s T800 for a dump truck at least till the CAT can prove it's self.
