A manhunt for an arsonist who has plagued Glendale for seven months was stepped up after two fires destroyed cars, a carport and a garage-dwelling in neighboring Burbank. The arsonist, who is blamed for as many as 50 fires, has been seen only once briefly, arson investigators said. The lastest outbreaks occurred an hour apart, Burbank Fire Marshal P. K. Spooner said. The first fire, at 1221 East Ave., destroyed four cars when flames spread to a carport. The second blaze destroyed three cars, a garage and an apartment unit over it at 435 E. Santa Anita Ave. No injuries were reported.