Chevrolet Vega - Engine

Engine

The Vega engine was a 2,287 cc (2.3 L; 139.6 cu in) inline-four with a die-cast aluminum alloy cylinder block, cast-iron cylinder head and single overhead camshaft (SOHC). The block was an open-deck design with siamesed cylinder bores. The outer case walls form the water jacket, sealed off by the head and head gasket, and the block has cast-iron main caps and crankshaft. The cast-iron cylinder head was chosen for low cost and structural integrity. A simple overhead valvetrain has three components activating each valve instead of a typical pushrod system's seven. An external belt from the crankshaft drives the five-bearing camshaft plus the water pump and fan.

Compression ratio for the standard and optional engine is 8.0:1, as the engine was designed for low-lead and lead-free fuels. The single-barrel carburetor version produced 90 hp (67 kW); the two-barrel version (RPO L11) produced 110 hp (82 kW). From 1972, ratings were listed as SAE net. The engine is prone to vibration, which is damped by large rubber engine mounts. The 1972 Rochester DualJet two-barrel carburetor required an air pump for emission certification and was replaced in 1973 with a Holley-built 5210C progressive two-barrel carburetor. 1973 emission control revisions reduced power from the optional engine by 5 bhp (3.7 kW), and its noise levels were lowered. H.E.I. ignition was introduced on 1975 engines.

Serious problems with the engine led to a redesign for 1976-1977. Marketed as the Dura-Built 140, the new engine had improved coolant pathways, redesigned cylinder head with quieter hydraulic valve lifters, longer-life valve stem seals that reduced oil consumption by 50%, and redesigned water pump, head gasket, and thermostat. Warranty was upgraded to five years or 60,000 miles (97,000 km). In 1977 a pulse-air system was added to meet stricter 1977 U.S. exhaust emission regulations and the engine paint color (used on all Chevrolet engines) changed from orange to blue.

In August 1975, Chevrolet conducted an endurance test of three Vegas powered by Dura-Built engines, advertised as a 60,000 miles in 60 days Durability Run. Supervised by the United States Auto Club, three pre-production 1976 hatchback coupes with manual transmissions and air conditioning were driven non-stop for 60,000 miles (97,000 km) in 60 days through the deserts of California and Nevada by nine drivers, covering a total of 180,000 miles (290,000 km). With the sole failure a broken timing belt, Vega project engineer Bernie Ernest said GM felt “very comfortable with the warranty."

A Motor Trend said "Chevrolet chose the 349-mile Southwestern desert route in order to show the severely criticized engine and cooling system had been improved in the 1976 model." In ambient temperatures between 99 °F (37 °C) and 122 °F (50 °C) the cars lost 24 US fluid ounces (0.71 L) of coolant (normal evaporation under the conditions) during the 180,000 miles. They averaged 28.9 mpg (8.14 L/100 km; 34.7 mpg) and used one quart of oil per 3,400 miles. Driving expenses averaged 2.17 cents per mile. One of the cars went on display at the 1976 New York Auto Show. The 1976 Vega was marketed as a durable and reliable car.