 The Z28 was re-introduced, as a model and not a RPO, to the buying public in the spring of 1977 as a "1977½" in response to increasing sales of Pontiac's Trans Am, which sold over 46,000 units in 1976 and accounted for half of all Firebird sales that year.The revived Z28 was powered by a V8 with four-barrel carburetor producing ( with California emissions equipment), with most cars sold equipped with air conditioning and an automatic transmission.The engine no longer came with the 4-bolt main bearing engine block, forged crank, forged pistons, big valve heads, and performance camshaft that had been part of the RPO Z28 Special Performance Package, the engine that had been shared with the Corvette LT-1 and L82 top-performance 350 engines from 1970-74.The LM1 engine was the most powerful Camaro engine and only available in the Z28 model.