(Reuters) - Chrysler Group LLC, the U.S. automaker majority owned by Fiat SpA, said on Thursday it will invest $238 million to boost engine and truck production in Michigan and add up to 1,250 jobs to meet new demand.

The company is spending $198 million to make its Pentastar V6 engine at the Mack I Engine Plant, which currently builds a larger engine for the Ram 1500 truck. Production will begin in early 2014 and Chrysler may add up to 250 jobs there, subject to market conditions.

The automaker is spending $40 million to install a flexible production line at its Trenton North plant, which can build both the V-6 engine and the Tigershark four-cylinder engine.

Chrysler also will add 1,000 new jobs on a third shift at its Warren Truck Assembly Plant, which builds the 2013 Ram 1500 truck. (Reporting By Deepa Seetharaman in Detroit; editing by John Wallace)