a period of two years. The stud-mounted independent ball rocker arm design patented by Pontiac engineer Clayton Leach, was scheduled for introduction in the Pontiac 1955 V8. GM forced the Pontiac division to share its valvetrain design in Chevrolet's new 265 V8 in 1955, so that both engines were introduced the same year with the same valve train design. A side note to Pontiac's V-8 was the engine was supposed to be introduced on 1953 cars, and all 53 & 54 Pontiac's chassis and suspension were designed for the engine that didn't make it into a Pontiac until late 1954. The reason this happened is that Buick division lobbied the corporation to hold back Pontiac's release because it affected Buick's release of the new OHV Buick V8 engine. A pushrod engine with hydraulic lifters, the small-block was available with an optional four-barrel Rochester carburetor, increasing engine output to , or in the Corvette. The short-stroke bore x stroke engine's bore spacing would continue in use for decades. Also available in the Bel Air sedan, the basic passenger car version produced with a two-barrel carburetor. Upgraded to a four-barrel Rochester, dual exhaust "Power Pack" version, the engine was conservatively rated at , and with the "Super Power Pack" it was boosted up to the power level of the Corvette. A shortcoming of the 1955 265 was its lack of any provision for oil filtration built into the block, instead relying on an add-on filter mounted on the thermostat housing, and that was an "option only". In spite of its novel green sand foundry construction, the '55 block's lack of adequate oil filtration leaves it typically only desirable to period collectors. The 1956 Corvette introduced three versions of this engine – with a single 4-barrel carburetor, with twin 4-barrels, and with two four-barrel carburetors and a high-lift camshaft. 3.875 in. bore family (1957–1973) The 283 had a bore. The stroke of the 283 was , like the 265. The 283, famous for being one of the first engines to make one hp per cubic inch, is also famous for being the evolutionary stepping stone that would later give rise to small blocks and to the "W" blocks, ultimately culminating in the Chevrolet big-blocks. The last of this family was the , which was a stroked 283 with a medium journal. 283 The V8 engine was bored out to in 1957, giving it