Oooh, two General Motors V8s within a cubic inch of each other! They must be almost the same engines, right? After all, the Chevrolet 454 and Pontiac 455 come from the same parent company, and each automaker engages in sharing parts, powertrains and platforms. That’s how we got the Cadillac Cimarron, in Pete’s name. These engines are definitely just different bores and strokes for different people.
Sharing parts is very common these days. For example, Ford and GM teamed up to create a 10-speed transmission. But it wasn’t always this way. In the 1960s and 1970s, each division of GM made its own engines with few or no interchangeable parts. And the Chevy 454 and Pontiac 455 are fantastic examples of how two large-displacement V8s from the same automaker can be as different as Star Wars and Star Trek.
However, despite their differences, the top versions were close in terms of performance. In 1970, Hot rod magazine achieved a quarter mile time of 13.44 seconds in an LS6 454 Chevelle. When Car and driver With another LS6 454-powered car on the track, a 1971 Corvette, the testers posted a 13.8-second quarter thanks to the ’71 LS6s having lower compression than the ’70 models. Meanwhile, Supercar Annual magazine put a ’71 Pontiac Trans Am with the 455 HO (High Output) through the quarter in 13.7, and Car and driver achieved 13,751 from a ’73 Pontiac Trans Am Super Duty 455.
The Chevy is oversquare and the Pontiac is undersquare
Oversquare motors tend to rev higher and deliver their torque at higher speeds, while undersquare motors are the opposite. This is reflected in the two engines we are looking at; while both make 320 pound-feet of torque at the rear wheels, the Chevy makes its peak torque at 3,600 rpm, while the Pontiac’s peak torque comes at 3,100 rpm. In terms of horsepower, the 1970 LS6 454 pumped out 450 gross horsepower at 5,600 rpm and the Pontiac 455 maxed out 370 gross horsepower at 4,600 rpm.
Until now we have avoided the term ‘big-block’ as this is another drastic difference between these engines. The 454 is certainly a big-block, but the 455 is not. That’s because most Pontiac V8 engines are virtually identical – albeit in different displacement states – and have the same 4.620-inch center distance. Meanwhile, the big block 454 has a center distance of 4.840 inches.
Do you want to make your crankshaft thicker or your head lighter?
Then there is weight. A Chevy big block 454 weighs about 685 pounds, while a Pontiac 455 weighs about 640 pounds. Both engines typically had an iron block and iron heads, while performance models received aluminum intakes. 454-powered Corvettes also received a set of rare aluminum heads in 1971. These heads were light enough to knock 40 pounds off the weight of a car.
Frankly, covering every difference between Chevy 454s and Pontiac 455s could fill an increasingly obscure list of design differences, like how the Pontiac 455 intake manifolds don’t seal the lift valleys. In terms of legacy, the 454’s performance declined in 1972, when the most popular option was the 270 net horsepower LS5. Conversely, Pontiac’s 455 extended the muscle car era with the 310/290 hp Super Duty 455 in 1973 and 1974. But while Pontiac’s 455 disappeared after 1976, Chevrolet’s 454 lived on in trucks. It wasn’t until the ’90s, when it powered the 1500 454 SS, one of the most criminally forgotten Chevy pickup trucks.
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