General Motors has placed production of its innovative Duramax 4.5 liter V8 diesel engine on indefinite hold, a high-efficiency unit that would have been used in the Chevolet Silverado and GMC Sierra light-duty trucks.

Production of the engine was scheduled to begin in the fall at the plant in Tonawanda, New York. Both GMC and Chevrolet will, however, continue to offer the Duramax 6.6-liter V8 diesel, a heavy-duty engine made in Ohio.

In a press release, GM expressed hope that the 4.5-liter engine will be built in the future. The unique design of the cylinder heads in the unit eliminated the need for the intake and exhaust manifolds and advanced castings are used for the crankshaft-bearing journals and the oil-circulation system. In operation, the engine runs as smoothly and quietly as any comparable gasoline unit currently on the market. GM did not rule out the option of selling the rights to the engine to another company.

News of the discontinuation of the project comes just three weeks before General Motors will learn from federal officials if the company qualifies for an additional $16.6 billion in assistance on top of the already $13.4 billion in government aid it has received.

The news is not good for the Tonawanda plant, where 400 workers, approximately one third of the plant's hourly employees, are on indefinite layoff status.