The Muscle Car era dawned in 1964 with Pontiac’s introduction of the GTO, based on their new mid-size Tempest. That same year, Chevrolet took the wraps off its new mid-sized car, the Chevelle, designed to compete with family cars from Ford and Plymouth. In late 1965, Chevelle tried to crash the muscle car party by offering the big block 396 cu. in. V8, but the muscle car horsepower race was in full swing and by then the competition had more powerful engines. Chevrolet decided to jump into the muscle car market with both feet and by 1970 offered what many call the best muscle car ever – the Chevelle SS 454 with the fearsome LS6 engine.
SS 454 most powerful Chevelle
The Super Sport package was a part of the Chevelle model lineup from the outset and was usually indicated by the “SS” logo on the exterior of the car. Initially, the SS package was available on most of the Chevelle Malibu models, but by 1970, Super Sport was limited to the coupe, the convertible, and the El Camino. After the big block 396 cu. in. engine became available, the SS name included the cubic inch displacement of the engine. Thus, the SS became the SS 396.
1970 marked the zenith of the muscle car wars and Chevrolet upped the ante by offering the Chevelle with the most powerful engine in its arsenal. Displacing a whopping 454 cubic inches, the LS5 version, rated at 360 horsepower, and the LS6 version, rated at 450 horsepower, were now available in the Chevelle. The LS6 was essentially a racing engine tamed just enough to drive on the street. Sporting an 800 cfm Holley four-barrel carburetor on an aluminum manifold, solid valve lifters, forged steel crankshaft and connecting rods, and forged aluminum pistons producing an 11.25:1 compression ratio, with a redline of 6,500 rpm, it was a prodigious power source. Many experts believe the LS6 was underrated and actually produced closer to 500 horsepower.
Gross vs. net horsepower
Before we get too obsessed with the horsepower rating of an engine, we should step back and look at how these ratings were obtained. Prior to 1971, all engines were rated by the manufacturer by their “gross” horsepower. The engines were tested on an engine dynamometer, not installed in a vehicle, and without any accessories, transmission, or exhaust system, and with maximized carburetor and ignition tuning settings.
While this rating may give the maximum horsepower of the engine, it does not represent the engine output when installed in a vehicle. The accessories, transmission, and exhaust system all absorb some of the engine’s horsepower before it gets to the driving wheels. The “gross” rating doesn’t give a true picture of what the engine will do in a vehicle.
By 1972, all manufacturers began rating their engines by “net” horsepower, with the engine connected to all accessories, a transmission, and an exhaust system. The net horsepower is less than the gross horsepower. All horsepower ratings for the 1970 Chevelle above are given in terms of gross horsepower, as was the custom of the times. In February 2011, Super Chevy tested a stock 1970 LS6 Chevelle on a modern chassis dyno where the net horsepower could be determined. Their results? The LS6 produced 283.25 horsepower at 5,600 rpm and 319.69 lb-ft of torque at 3,900 rpm. A big difference from the gross figures, but the bottom line is that the LS6 was the quickest thing around in 1970.
How fast was the SS 454 LS6?
Heacock Classic, the collector car insurance folks, considers the SS 454 LS6 to be “America’s King of the Streets.” To back up this opinion, they collected test data from several car magazines that conducted quarter-mile tests back in 1969 and 1970. In Heacock’s opinion, there were only two “undisputed muscle car heavyweights” in 1970 – the LS6 Chevelle and the Mopar Hemi. After a head-to-head comparison, the results shown below were close, but supported Heacock’s choice of the Chevelle as the King.
¼ Mile Time
|13.2 s||106||Super Stock & Drag Illustrated||May 1970|
|13.44 s||108.17||Hot Rod|
|HEMI||13.34 s||107.52||Super Stock & Drag Illustrated|
|HEMI||13.85 s||104||Rodder & Super Stock|
Chevelle SS 454 was top dog in 1970
On any given day in 1970, a well-tuned SS 454 with a good driver could take any other car to the woodshed. But their top-dog status was short-lived, as the end of the muscle car was looming on the horizon. The coming of safety standards that made every car heavier, coupled with emission control regulations and unleaded gas that sapped engine horsepower, spelled doom for high-performance muscle cars. The switch to net horsepower ratings in by 1972 exacerbated the situation by giving the public the perception that engine power was dropping even more than it actually was, turning them off to any performance car.
After making 4,475 LS6 Chevelles, Chevrolet took a small step into the future by cancelling the LS6 option in May of 1971. Hot Rod Magazine summed up the SS 454 best when they said, “The past is gone. The future may never see a car like this. It is one of the brutes.”
My Classic Garage – http://myclassicgarage.com/marketplace/knowledge_base/1970-chevrolet-chevelle
Cars with Muscles – http://carswithmuscles.com/1970-chevrolet-chevelle-ss-454-ls6-chevelle-ss-396/