Muscle Cars, 1971 Chevelle SS, LS-5 454-4bbl

Chevrolet Muscle Cars 1971 Chevelle SS 454

In 1971, the anticipation of the upcoming low-lead and unleaded gasoline’s, the tightening of emission requirements, and the use of catalytic converters to be used on 1975 and later models led to GMs re-design of the Muscle Car engines. To facilitate the use of lower octane fuels, all engines featured low compression ratios, 9 to 1 and lower. The high performance engines of 1970 and earlier had compression ratios of 10.25/11.25 to 1. This move reduced horsepower ratings of big block engines to 300 hp for the 402 V8, although the LS-5 454 option had an increase in horsepower to 365. The insurance wrath of 1970 played a key role in the declining sales of the Muscle Car. The base form of the Chevelle SS changed specifically from a performance package to a trim package.

The 1971 Chevelle SS, (different from the 1964-65 model of Chevelle SS, 396 engine) had a 350 V8 engine with a 2-bbl carburetor rated at 245 gross (165 net) hp, with the optional 4-bbl 350 V8 the horsepower was slightly increased to 275 gross (200 net). The big blocks, now an extra cost option, included the 402 V8, 300 gross (270 net) hp and the LS-5 454 V8 at 365 gross (285 net) hp. With this extra cost option Chevelle SS managed to hold its Muscle Car classification.

The base Chevelle coupe in mid 1971 thru 1972 was offered as the “Heavy Chevy” model with special striping and appearance features.. The “Heavy Chevy” came with any available engine from the 307 2-bbl to the 402 4-bbl. The 454 V8 big block was only an option to the Chevelle SS package. It was not an option with “Heavy Chevy” version.