TOWN OF TONAWANDA — Tonawanda’s engine plant appears to be running at a slightly higher rpm these days.

Plant managers and labor officials on Wednesday toured a portion of the plant that has been vacant since 2004, but is now home to a new training center and parts-assembly operation.

“We were told that this building would never open up again,” Bob Coleman, UAW Local 774 chairman, said of what is known as Plant Four, located off Kenmore Avenue.

He said labor representatives and company officials worked together to convince GM to open what’s called a Logistical Optimization Center at one end of the 1.1 million square foot building.

As many as 120 tier-two workers — who earn less than traditional UAW wages — will be hired at the site, which eventually will ramp up to three shifts per day. Workers will produce “kits” of raw parts used by operators on the assembly line.

Workers will assemble five different parts kits for building each engine the plant produces, with some kits having up to 12 variations.

Once up and running, keeping up with the demand for parts on the line could mean packaging more than 500 of each kit per shift. Such operations are often located off-site, Finch said.

He and union leaders lauded a cooperative spirit for helping convince GM brass that the new, in-house operation would be worthwhile. The particular process in which the kits are produced is unique among the nation’s 54 GM plants, and could serve as a model for others across the country.

“We’re going to be hiring hundreds of people who’ll be coming into this facility in the next year and a half,” Plant Manager Steve Finch told reporters before leading them to the other end of the building, now home to the training facility.

With a commitment for $900 million in work producing three new engines at the facility, managers and labor officials on Wednesday said they expect to add new jobs in addition to recalling about 93 workers now on layoff.

Along with the new investment comes the need to train the plant’s existing workers on the new lines.

Finch said the upper floor of the wing now housing the school was a “disaster area” home to defunct machinery and office furniture just a few months ago.

Workers have since transformed the building now home to a virtual assembly line, break areas and 10 new classrooms now offering 275 different courses to re-train the plant’s skilled workforce or introduce new plant workers to the job.

The first class of 10 students began Monday in robotics training.

The facility is built to accommodate up to 166 students at a time and has been courted by other businesses in the nearby industrial corridor for their own training needs.

Following an eight hour class, students on the model assembly line must produce 28 wooden models of vehicles in a half an hour, free from scrap, defects, safety incident or other demerits.

Plant Four, not seen by the public for almost a decade, once built Pratt and Whitney aircraft engines during World War II, and most recently had been used to produce 3.1 liter and 3.4 liter GM engines.

Wally Michels, a union representative behind the new kit assembly line, said about $5 million in obsolete machinery was scrapped to help fund startup of the offshoot business.

He said cooperation between labor and management was crucial in Tonawanda’s newest investment, a message stressed by all of the officials gathered for Wednesday’s announcement.

Once employees are recalled, GM component holdings workers in Lockport and Rochester will also have the opportunity to move to Tonawanda, a statement issued by the plant states.

That, officials say, will free up component holdings plants in those areas to hire new employees.

“The benefits of this infusion of new business are so far reaching,” Finch said, adding also that some 250 construction workers per day continue to make improvements to each of the plant’s three main buildings.