General Motors Corp.'s has begun a $250 million project to renovate and expand its Baltimore auto plant and plans to spend another $200 million on a new paint facility.

GM is expected to invest in automobile painting machinery intended to meet stricter air emission standards set for the future as part of what one company spokesman called "Phase II" of the expansion project.

The first phase of GM's efforts applies only to the expansion and renovation of the plant's body shop and assembly line and parking lots to enable it to produce a new front-wheel-drive car for the 1983 model year.

The paint operation will be costly.

"It's very expensive. You have to replace everything, all the equipment, including the spray guns, spray booths, all tooling, and piping from the paint holding tanks," said a GM spokesman in Detroit.

City officials have compared the scope of GM's future plans to the combined development of Inner Harbor and Charles Center, the city's downtown modern office district.

Maryland Department of Economic and Community Development officials could not recall an industrial project equal to the combined size of the GM effort anywhere in the state in the past decade.