1971 Novas were similar to the previous year. The 396 cu in (6.49 L) engine was replaced with the 350 cu in (5.7 L) in the SS model. 1971 also saw the introduction of the Rally Nova, a trim level that only lasted two years (until it resurfaced in 1977). The Rally kit included black or white stripes that ran the length of the car and around the back, a Rally Nova sticker on the driver's side of the hood, Rally wheels, multi-leaf rear springs, and a "sport" body colored drivers side mirror that was adjustable from the interior. The well-hyped Vega stole sales from the Nova this year, but the compact soon would enjoy a resurgence of popularity that would last deep into the 1970s.
The 250 cu in (4.1 L) six-cylinder engine was now the standard Nova engine with the demise of the 153 cu in (2.51 L) four-cylinder and 230 cu in (3.8 L) six-cylinder engines. The 307 cu in (5.03 L) and 350 cu in (5.7 L) V8s were carried over from 1970 and all engines featured lowered compression ratios to enable the use of unleaded gasoline as a result of a GM corporate mandate that took effect with the 1971 model year.
After 1971, other GM divisions began rebadging the Nova as their new entry-level vehicle, such as the Pontiac Ventura II (once a trim option for full-size Pontiacs to 1970), Oldsmobile Omega and the Buick Apollo. This was considered to build brand loyalty with respective GM divisions although the company later fused their badge engineering with platform sharing to cut expenditures. Interestingly, the initials of the four model names spelled out the acronym NOVA (Nova, Omega, Ventura, Apollo).
Source: Wikipedia, 2014