> Main > Diesel Index > FAQ > ISB head onto a 12V engine
ISB Head Transplant to a 12 Valve Engine
Visit Geno's Garage
for Truck accessories.
Geno's Garage Truck Accessories

Subject:   24-valve B-Series, not ISB
Date:       Mon, 08 Feb 1999 16:43:03
From:      Josh Berman

> Q: Can a 24 Valve ISB head be installed on my 12 Valve engine
> for a performance improvement?

        The head bolt patterns between the ISB and the B are the same. There would definitely be challenges in doing this swap, the most significant of which would be, in my opinion, that you'd have to fabricate a set of high-pressure injection lines that worked with the P7100 (for '94-98 trucks) and the ISB head.

        The ISB's injector & line setup is different from any previous B-series setup, so you wouldn't be able to use old hardware to fit the ISB. On ISBs, the fuel lines attach to the "edge" of the head, and a high pressure fuel connector takes the fuel from the "edge" in to the center where the injector is.

        You would also have to change pistons, since the piston bowls are offset in the B (due to the offset, angled injectors), but the bores are the same, so ISB pistons would fit w/o problems.

        Some changes were made to the camshaft lobe proflies for the ISB, but they were made with several things in mind, including the 4-valve/cyl head and the variable timing capability of the VP44. I'm not sure what the right answer would be, but I'm not sure either cam would work well with the ISB head on a "mechanical" engine.

        You may also need custom-length (or "adjustable") push tubes, since the tappets for the ISB are slightly different compared to B-Series tappets.

        It's not impossible, just difficult (meaning, it'll cost $$$ to get right :-)

        -Josh Berman
Joshua Berman           MidRange Service        Cummins Engine Company
Cummins Homepage:

Last page update: May 3, 2001