a OHV V8 had begun, but moved along slowly. When Robert Critchfield took over as general manager in 1952, he launched an ambitious plan to move Pontiac into the upscale, mid-range market occupied by Oldsmobile, and that demanded V8 power. A new engine was fast-tracked, its relatively late start allowing it to take advantage of developments proven in the Oldsmobile V8 and Cadillac V8. As a result, it was remarkably free of teething problems. During 1951–1952, Pontiac had 23 V8-equipped 1953 model production prototypes running tests on the GM proving grounds. Pontiac planned to produce the 1953 models with the V8, but Buick and Oldsmobile appealed to GM management and earned a 2-year delay. The main innovation of the Pontiac engine was reverse-flow cooling and the stamped rocker-arm system, which had been devised by Pontiac engineer Clayton Leach in 1948. At the request of Ed Cole, general manager of Chevrolet, the layout was also used by the Chevrolet V8 released in 1955, an exception to the customary GM policy of allowing a division one year of exclusive use of an internally developed advance. Displacement began at and grew as large as by 1970. Pontiac continued to manufacture its own engines, distinct from Buick, Cadillac, Chevrolet, or Oldsmobile, until 1981. Pontiac engines were used in its U.S.-market cars; Canadian-built Pontiac automobiles generally used Chevrolet engines. From 1955 through 1959, the Pontiac V8 was also used in some GMC pick-up trucks. Federal emissions standards and the drive towards "corporate" engines shared among all GM divisions led to the progressive demise of the Pontiac V8 through the late 1970s. The last "true" Pontiac V8s, a , ended production in early 1981. Design The 1955-up Pontiac V8 that finally reached the public was an overhead valve engine with cast iron cylinder heads and block and wedge-shaped combustion chambers. An innovative design feature was mounting the rocker arms on ball pivots on studs set into the cylinder head, rather than using a separate rocker shaft. Along with being cheaper to build, this allowed more consistent valve action with less weight than a conventional shaft. All Pontiac V8s from 1955 to 1959 were reverse cooled, known as the "gusher" cooling system. It was removed from the design for the 1960 model year because designers moved the generator and the power steering pump from atop the front of the engine down to the front of the heads