LAS VEGAS — Cummins Inc. displayed the forthcoming Cummins Westport 12-liter natural gas engine as part of its 2013 vocational engine lineup, which it unveiled here this week at the World of Concrete Show.

Slated to begin limited production in April, the ISX12 G is based on Cummins ISX12 diesel and will offer ratings from 320 hp to 400 hp, and up to 1450 pound-feet of torque, the engine maker said. It will be certified for 2013 Environmental Protection Agency emissions regulations when production begins.

Both the ISX12 G and the Cummins Westport ISL G natural gas engine will run on compressed natural gas, liquefied natural gas or biomethane, the company said. The ISL G, which is also 2013 EPA-certified, is available with power ratings from 250 hp to 320 hp. The ISX12 G will have an optional engine brake and will be mated to automatic and manual transmissions, Cummins said.

Cummins also displayed the rest of its vocational line, which includes the diesel-powered ISX12 and the ISL9, a 9-liter diesel. Both engines are certified for 2013 EPA-compliant and meet greenhouse gas and fuel efficiency rules that take effect in 2014, Cummins said.