But what really set the Bonneville apart was a larger V-8 with Rochester fuel injection, a pet project of new division chief engineer Elliot M. "Pete" Estes. ("Fuel injection" was written in large chrome letters on the deck and front fenders, underlining the importance attached to this feature; oddly though, the Bonneville bore no Pontiac nameplate!)

Having progressed through 316.6 cubic inches for 1956, the Pontiac V-8 was stroked to 347 cubic inches (bore and stroke: 3.94 × 3.25 inches) for all models "except the new hot one", which got a bore job (to 4.06 inches) for 370 cubic inches.

The 1957 Bonneville's fuel injection was a mechanical, continuous-flow type conceived by General Motors Engineering and engineered for production by Harry Barr and Corvette wizard Zora Arkus-Duntov. It was similar to that year's "Ramjet" system introduced at Chevrolet, with fuel and air meters on a special manifold instead of the normal carburetor and intake manifold.

Both squirted precise amounts of fuel directly into each port, but the Pontiac system was tidier, with a cast manifold header, combined (instead of separate) manifold heater and pipes, and a lower-mount fuel meter.