page_title: Pontiac V8 engine
section_title: 400
hierarchical_section_title: Pontiac V8 engine / Small-journal engines:1955-1981 / 400
caption_attribution_description: English: The 400ci Pontiac V8 engine in a 1976 Pontiac Firebird Trans Am 50th Anniversary Limited Edition. 2590 of these special editions were built, the package consisted of black paint with gold trim and some decals.
context_page_description: The Pontiac V8 engine is a family of overhead valve V8 engines manufactured by the Pontiac Division of General Motors Corporation that made its debut in 1955. Pontiac began as a "companion" to the Oakland division of the General Motors line of automobiles in 1926. Pontiac successfully competed against more-expensive inline four-cylinder models with their inline flathead six-cylinder engines. After outselling Oakland, Pontiac became the sole survivor of the two by 1932. In addition to the inline 6, Pontiac used the Oakland V8 for one year, 1932, debuting an inline 8 in 1933. The two inline engines were used through 1954, when Pontiac unveiled its OHV V8 in 1955. The development of this V8 dates back to 1946, when engineers began considering new engine designs for postwar cars. They came up with a 269-cubic-inch L-head design. Pontiac engineers tested their 269 cu in V8 in 1949 or 1950 against a downsized Olds rocket V8 overhead engine. The Olds engine was a 303 cu in, Pontiac reduced the size to 270 cu in in for testing against the 269 engine. The test results showed Pontiac that an L-head engine simply couldn't compete with overhead valve V8 engine designs.
context_section_description: For 1967, Pontiac retired the 389 cu in (6.4 L) and replaced it with the 400 cu in (6,554 cc), a 389 bored-out by +0.06 in (1.5 mm) to a bore and stroke of 4.12 in × 3 ³⁄₄ in (104.6 mm × 95.3 mm). The 400 remained in production through the 1978 model year, with 1979 cars receiving engines produced the previous year.
  In 1967, the cylinder head design was improved for the 400 4-barrel engine. The valve angle was reduced from 17 degrees to 14 degrees for better breathing. 1967 was the last year for closed-chambered heads. The "670" head was a 1967-only casting, and the only PMD head to have a closed chamber with the new 14 degree valve angle. The 400 2-barrel kept the 17 degree valve angles for '67; starting in '68 all Pontiac V8s went to the 14 degree valve angle. Pontiac went to open-chambered heads in some 1967 models and all 68 and up to improve power, engine breathing and reduce emissions. The valve size increased as well, to 2.11 in (53.6 mm) intake and 1.77 in (45.0 mm) exhaust valves on high-performance heads. Low-performance and two-barrel applications, the standard engine in full-sized Pontiacs, got 1.96 in (49.8 mm) intake and 1.66 in (42.2 mm) exhaust valves and pressed in rocker arm studs.
  The four-barrel 400 was a popular performance option for many of Pontiac's cars. When fitted with other high-airflow components, it produced a good balance of low-end torque and higher-RPM power.
caption: 400 cu in engine in a 1976 Trans Am 50th Anniversary
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