The Chevrolet Chevelle SS

American Muscle - Back in 1970 things looked great. The muscle car craze was in full swing introducing barrage of different V8 machines.  For 1970 horsepower and displacement were up, and there was a muscle car to fit everyone's taste from all the different vehicle manufacturers. Unfortunately high insurance costs and legislative action were catching up with the muscle car. The low-performance era was right around the corner, and by 1975 performance in most cars would die a slow and painful death. Sad but painful truth.

Since its first model year -1965, the Chevelle SS had grown in popularity. By the late 1960s, the Chevelle SS with its strong faithful following was one of the more popular muscle cars.  For 1970 even better things were in store for the Chevelle SS. 

Chevrolet Chevelle SS

Due to an internal edict at General Motors, only full-size cars and the Corvette could have engines with displacements larger than 400 cubic inches. Because of the edict the 1965 to 1969 Chevelle SS only came equipped with a 396 big block V8. However by the late 1960s Chevrolet got around this by allowing its Central Office Production Order (COPO) program to offer its full range of 427 V8’s to customers who special ordered COPO Chevelle’s and Camaro’s. Though COPO allowed the production of some legendary 427 powered Chevrolet muscle cars, total production was very low.

In 1970, General Motors decided to lift the ban and Chevrolet's response to that was the introduction of the 454 (7.4 litre)V8 as a 1970 Chevelle SS option. The 454 V8 is a member of the Chevrolet Mark IV big block V8 engine family.  The first Mark IV engine was the 396 V8, which first saw its introduction during the 1965 model year. In 1966 the Mark IV 427 V8 joined Chevrolet's engine lineup alongside the 396.

Chevrolet Chevelle SS

For 1970, the 454 was not only new to the Chevelle SS but also to Chevrolet. The legendary 427 big block V8 was the largest displacement Chevy V8 in 1969. For 1970, Chevrolet decided to increase the 427's stroke, which increased the displacement to 454 cubic inches. The 4.25 in. bore and 4.0 in. stroke of the 454 are numbers that bring a smile to any muscle car fan's face. Chevy fans cheered the increase in     displacement since larger displacement meant more horsepower and especially more  

torque.                                             

Chevy provided two separate SS options for the 1970 Chevelle, the SS 396 (Z25) option and the SS 454 (Z15) option. With the SS 396 option one could choose from 396 V8s - the 350 horsepower version and the 375 horsepower derivative. Chevy's little secret concerning the 396 for 1970 was that it no longer displaced 396 cubic inches but rather 402. Chevy added a .030 in. overbore on the 396 block pushing its displacement up to 402 cubic inches.  For some unknown reason Chevy decided it was best to call the 1970 402, a 396.

The SS 454 or Z15, a mid-year option, gave the 1970 Chevelle SS buyer two powerhouse 454 V8s to choose from - the LS5 and LS6.  The LS5 454 was rated at 360 horsepower in the 1970 Chevelle SS, but 390 horsepower in the 1970 Corvette.

Chevrolet Chevelle SS

On paper the LS6 was the most powerful production engine during the muscle car golden era. The Chevelle SS LS6 consistently obtained 13 second range 1/4 mile times in magazine tests back in the day, which is extremely impressive when you consider a LS6 Chevelle SS has a weight of around 4,000 lbs with driver and fuel. The fastest LS6 1/4 mile time recorded by an automotive magazine (back in the day) was in the November 1969 issue of Car Craft. Car Craft piloted their stock '70 Chevelle SS through the 1/4 mile in 13.12 seconds at 107.01 mph. As many people think muscle cars are, the 1970 Chevelle SS  was also no slouch around the turns with its heavy duty F41 suspension which not only included heavy duty suspension components but also 14x7 inch wheels and F70x14 tires.

By 1970 most muscle cars were leaving the dealer lots loaded with many factory options, a far cry from the stalwart muscle cars of a few years prior. The Chevelle SS LS6 with its many available options was no different. It was not cheap, it started at around $4,500 (roughly R47 370) and the price increased as more options were added. Back in 1970 the average family income was around $10,000 (R105 267), making a Chevelle SS LS6 454 an expensive purchase for the average buyer however it was worth every penny.

  

The LS6 454 returned again in 1971 but it was only available on the Corvette, producing 425 horsepower. The horsepower loss was due to a loss in compression. All GM engines in 1971 suffered a substantial compression ratio drop in order to meet new unleaded fuel standards. The party was now officially over, and the new race for auto manufacturers was to see how fast high performance engines could be detuned or eliminated. After 1971, the 454 left and never returned. And soon after, the 1973 Chevelle SS became the last Chevelle to wear the SS emblems. 

Every once in a great while a freak of nature occurs, something so different from the average or norm that it blatantly stands out. In 1970 the Chevelle SS LS6 was just that - a freak of nature. It was the complete apex of an era of skyrocketing horsepower ratings when it seemed like the sky was the limit. Looking back now, it's quite clear the 1970 Chevelle SS LS6 was the Mount Everest of the muscle car golden era.