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  Oldsmobile's modern overhead valve V8 was introduced in its 1949 models. This engine was originally dubbed the "Rocket" engine, a name used on Oldsmobile V8s into the 1970s, including the 455-cubic-inch V8. The 455 engine was the largest displacement engine Oldsmobile ever produced, and originally it was only available in full-sized cars. When a General Motors mandate was lifted in 1970 that prevented any engine over 400 cubic inches from being installed in its smaller cars, the 455 was installed in midsize Oldsmobiles, such as the Cutlass and the 4-4-2.
  
  

General Information

• The 455-cubic-inch V8 was introduced in full-sized 1968 Oldsmobiles. It was standard equipment in the Ninety-Eight and Tornado, and it was an option in the Eighty-Eight models. The cylinder bore was 4.126 inches and the crankshaft stroke was 4.25 inches. Engines with two-barrel carburetors had a compression ratio of 9.0:1, while engines equipped with four-barrel carburetors had a compression ratio of 10.25:1.
  
  

Outputs

• Two-barrel 455 engines had an output of 310 to 320 horsepower at 4,200 rpm and 490 to 500 pound-feet of torque at 2,400 rpm. The output on a four-barrel 455 ranged from 365 to 400 horsepower at 4,600 to 5,000 rpm and 500 to 510 pound-feet of torque at 3,000 to 3,200 rpm. After 1971, the power outputs on all Oldsmobile engines dropped, but on paper only. A new method of determining an engine's horsepower was adopted industry-wide in 1972 that resulted in much lower horsepower and torque ratings. The power output of the 455 engine continued to drop in the 1970s because of emissions requirements until the power plant was discontinued after 1976. The last of the 455 engines had only 210 horsepower.
  
  

Torque Specifications

• When rebuilding or assembling an 455 engine, the tightness of all engine fasteners needs to be checked with a torque wrench. The main bearing cap bolts need to be tightened to 120 foot-pounds. Cylinder head bolts need to be tightened to 80 foot-pounds. Connecting rod bolts should be tightened to 42 foot-pounds. The oil pump retaining bolts need to be tightened to 35 foot-pounds, but the oil pump cover should only be tightened to 8 foot-pounds. The oil pan retaining bolts on the underside of the block should be tightened to 12 foot-pounds. The valve cover bolts need only 7 foot-pounds of torque, while the oil filter element needs to be tightened to its base using 20 foot-pound of force.