The new year is bringing more changes to the region’s auto manufacturing plants.

General Motors’ Lockport plant is completing investments that began last year. GM’s Town of Tonawanda plant is about to launch another new engine line. And Ford Motor Co. is starting to capitalize on an investment announced in 2011.

While the plants’ production levels ultimately depend on customer demand for vehicles, the automakers seem generally upbeat about their prospects this year.

The GM Components Holdings Plant in Lockport, formerly a Delphi operation, will complete $44 million worth of investments that started in 2011, said Pat Curtis, the plant manager.

“We’re looking at a solid business plan for 2013,” he said. Parts for trucks remain a big part of the business for the Lockport complex.

The Lockport site remains a significant source of jobs for the region, with about 1,600 hourly and salaried employees. And the plant’s economic impact adds up to wages of $85.8 million, payroll taxes of $16.7 million and property taxes of $915,000, according to GM.

The Lockport site makes products including radiators, condensers, heater cores, evaporators and HVAC modules. It supports a range of Chevy, GMC, Buick and Cadillac products.

GM’s Tonawanda plant has been on an upswing since two new engine lines with a combined investment of $825 million were announced in 2010. The first of the two lines, involving the four-cylinder Ecotec 2-liter and 2.5-liter engines, went into production last year, supporting the Chevrolet Malibu and Cadillac ATS. The ATS’ engine made’s 2013 list of the top 10 engines for North America.

The new engine line is set to launch in the first quarter. GM will make V8 and V6 engines, playing the lead role in engines supplied for new versions of the Chevrolet Silverado and GMC Sierra trucks. The V8 is also being used in the next-generation C7 Corvette.

All of this new activity pleases Steve Finch, the plant manager. “I couldn’t be happier. This is what we had hoped and prayed for in all the lean years.”

Workers implementing the new engine line will be able to apply lessons learned from the launch of the Ecotec last year, since the two lines use similar equipment.

The new engine lines are also bolstering employment at the Tonawanda complex. The site currently employs about 1,115 hourly and salaried workers, but the total is expected to reach about 1,600 by next year, as the new engine lines go into full production. The additional employees will be a combination of workers coming from other GM facilities, including in Lockport, and new hires, Finch said.

The Tonawanda plant will mark a milestone in 2013: its 75th year of production. An open house is planned for August.

Last year was a transition year for GM Tonawanda, with one new engine ramping up and some older lines being phased out. As a result, total engine production was about 272,000 units, compared to 342,190 in 2011, according to GM statistics.

In 2011, GM Tonawanda’s economic impact consisted of wages of $75 million, payroll taxes of $16.1 million, and property taxes of $950,000, according to the automaker.

Looking ahead to this year, Finch said: “Right now, everything I see and hear about in the industry is, the volume and the outcome and the focus for us looks pretty strong.”

The GM plants in Tonawanda and Lockport have proved themselves survivors, no small feat as the automaker has reshaped its operations and cut facilities. And the pressures have not abated: Last year, GM announced it would close a hydrogen fuel-cell research operation in Honeoye Falls, near Rochester, and move the work to Michigan, taking away 220 jobs.

Ford’s plant on Route 5 in Hamburg, which produces stamped body parts for a host of Ford family vehicles, is starting to take advantage of previously announced upgrades. Ford in 2011 agreed to commit $136 million to the facility as part of a new contract between the automaker and the United Auto Workers.

The Hamburg plant stamps parts for vehicles such as the Ford Edge and Flex and Lincoln MKX and MKT, which are assembled in Oakville, Ont.

Todd Nissen, a Ford spokesman, said the automaker has started doing some work at the Hamburg plant in preparation for adding new equipment, but he could not specify when the new equipment would be implemented.

The plant is also in line for more workers. Rep. Brian Higgins, D-Buffalo, has previously estimated that as new equipment is installed and work ramps up, the plant would add about 400 workers. The timetable for those new jobs is unclear.

In the Town of Tonawanda, the Goodyear Dunlop North American Tires’ plant plays a supporting role in the auto industry, producing tires for commercial trucks, passenger cars and motorcycles. The complex employs about 1,300 people and has just named a new plant manager, John Romero.

A handful of jobs from the Tonawanda plant are being moved to Goodyear’s headquarters in Ohio. Meanwhile, a contract with the United Steelworkers of America covering hourly workers at the Tonawanda site is set to expire this summer.

Cummins Inc.’s engine plant near Jamestown remains another prominent player in the region’s auto manufacturing industry, with about 1,600 employees.

Jon Mills, a spokesman for Indiana-based Cummins, said the plant is coping with continued uncertain economic conditions. As has been the plant’s habit, it first cuts back on the temporary workers it uses to augment the workforce when demand slows.

No new financial investments at the plant are planned for this year, although the facility is launching a version of an existing engine that will be compliant with 2013 Environmental Protection Agency standards, Mills said.

Mills said the Jamestown plant “continues to be an important part of Cummins,” but said the company has had to adjust to the market. “Obviously Cummins has had to take steps over the past several years to become more diversified. We’re prepared for long-term success.”