Both the 425 and 368 are small-bore versions of the durable 472 (which was introduced in late 1967 for the '68 model year). The larger 500 had the 472's bore but a longer stroke. This engine family was the last Cadillac cast-iron engine, and the last 'big-block'. During this period, an assortment of engines were offered in the interest of fuel economy. These included the Buick 252 V6, diesel Oldsmobile 350 V8, and of Cadillac's own "HT-4100" small block V8, an alloy unit with cast iron cylinder liners which was troublesome and prone to early failure. The first two were dropped in 1982 once gas prices began falling while the latter persisted through 1986.