I was under the impression that all M11 engines had the black top and that ISM engines had the red top—but now I'm not certain. I also had thought that the 450 Hp ISM began to be installed in the 1997 models but more recently I've read that they began with the 1998 models. Can any straighten out my confusion? Thanks!
Our 2000- 320-42 has the red top with 239,000 miles
That is also my understanding that red tops will be ISM 450. My 2000 is a red top ISM 450.
If a red valve cover in '97 it is either the M11 Celect or the Cel;ect Plus. (the engines between M11 and the ISM) Totally different than the M11 with the black valve cover. The ISM is same as the Celect Plus but they added the Interact System (ISM) these could be in the real late '98 coaches.
Mike
Learn something new every day, I thought the Cummins N14 was known as the "Red Top" engine.
ISM 450 with red top in my sold 2000 U320
Also, Cummins is no longer supporting N-14 engines, rebuilds, parts etc.. Take care of what you have.