when did dodge go to the 24 valve
Ram Pickup A natural-gas-powered engine debuted for 1995 but was not popular and was only used in fleet vehicles on a very limited production run. The Cummins B Series engine was switched from the 12-valve to the 24-valve (ISB) version in the middle of the 1998 model-year Dodge Rams due to emissions regulations. The ISB featured a new computer-controlled injection pump, 24-valve head design, and an electric fuel pump.