Chevrolet's 1970 250-cubic-inch in-line six-cylinder engine served as the base powerplant for Chevy and other General Motors' cars from 1966 until 1985 for the North America market and until 1998 for foreign markets. It often served as an alternative to Chevy's other base engine, the 230 straight-six. Most notably the 250 Six powered early Camaros, although few buyers purchased it.
Chevrolet has a long history of producing sturdy in-line six-cylinder engines, but it hadn't always been that way. The automaker stubbornly clung to four-cylinder versions long after its competitors embraced the straight-six. However, in 1928, it developed the 215.5-cubic-inch "Stovebolt" Six, so named for head blots looking like stove bolts. It followed in 1936 with the 235.5-cubic-inch Blue Flame Six that provided standard power for Chevys until 1962. In 1966, Chevrolet developed the 250 straight-six that became the favored base engine for most Chevrolets through 1998.
1970 250 Specs
The 1970 version of the 250 Six featured the same horsepower and torque rating as the 250s dating to 1967. It featured a 3.875-inch bore and 3.53-inch stroke with a modest 8.5-to-1 compression ratio. Its firing order was 1-5-3-6-2-4. The engine generated 155 horsepower and 235 foot-pounds of torque. The 1970 model year was the 250's best as horsepower ratings steadily declined due to more strict federal emission standards. The 250's horsepower dropped to 145 in 1971, then to 139 in 1972, 100 in 1973, and then up slightly to 105 by 1975. Its compression ratio dipped as low as 7.7-to-1.
Features and Identification
The 1970 250 featured a single-barrel carburetor, although two-barrel versions were often used. The 250 received the two-barrel carb on Chevy trucks after 1978. The casting number on the 250 manufactured between 1968 and 1984 was 328575; the 250 also powered Buicks and Oldsmobiles. For 250s manufactured from 1968 to 1976 that powered Chevys, Buicks and Pontiacs, the casting number was 328576. The 250s powering only 1966 to 1976 Chevys had a casting number of 358825.
The Chevrolet 250 served as the base engine for the following vehicles: 1966 to 1984 Chevrolet passenger cars, the 1968 to 1976 Pontiac Firebird, the 1968 to 1970 Pontiac Tempest, the 1968 to 1976 Pontiac LeMans, the 1968 to 1972 Oldsmobile F-85, the 1968 to 1971 Buick Skylark and the 1968 to 1979 Camaro. It also powered the 1969 to 1979 Checker Marathon and the Brazilian 1968 to 1992 Chevy Opala.
Chevy offered three variants of the original 250. The L22 six-cylinder generated 105 horsepower and 190 foot-pounds of torque to power 1967 to 1979 Chevys. An LD4 straight-six was produced only in 1978. The LE3 saw production from 1979 to 1984. All three engines derived from the 1970 Chevy 250.
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