The Chevelle interior has been redesigned for 1970 and the exterior has also been renewed; its now squared up; more symmetrical looking than last year. The sedans are on a 112 inch wheel base and have a curb weight of 3,520 lbs (1,597 kg). There is a full range of models to tempt consumers, but the largest engine option is only offered for the Malibu coupe and Malibu convertible or the El Camino pick-up. The 1970 454 engine is the most powerful ever fitted into the Chevelle, but only for this one year, with the succeeding years offers the performance has been retarded to conform to EPA mandated pollution control regulations.
The best news for 1970 is the latest 454 power option derived from the Mark IV block. The LS6 big block is a 453.96 inch (7.4 L) displacement version on the table for the Chevelle SS this year. This cast iron engine boasts four bolt main caps, forged steel crankshaft and push rods, with the aluminium pistons, also turned out by a forge. The engine was only available as the RPO Z15 SS Equipment option, factory equipped to produce 360 (268 kW) in the base version. The LS6 454 putting out 450 hp (340 kW) is as good as it will ever get for a stock Chevelle. Either one of the 454 engine power options will be equipped with dual exhaust power and could optionally have cowl induction. This ultimate Chevelle engine has a cylinder bore of 4.250 inches (108.0 mm), pistons a 4 inch stroke and the firing chamber has a tight, 8.75:1, compression ratio. The low-rise aluminum intake manifold sports a Holley model 4150, cfm 780 four barrel carburetor, the heads have 2.910” intake valves, and 1.880” exhaust valves, while the extra-beefy dimpled connecting rods are engineered for handling high the high stress of performance driving. The lifters are solid ones and the pulleys are deeply grooved for more efficient power transfer. The ‘70 Chevelle is under rated by Chevy at 450 bhp @ 5,600 rpm and producing a more accurate, 500 lb-ft. of torque @ 3,200 rpm. Field testing done in 1970 strongly indicate well in excess of. 500 bhp, but the figure cannot be backed by any data available now. Super Chevy Magazine did conduct and publish dyno tests on a well-tuned assembly-line produced LS6 engine. The power plant will deliver a peak of 283 hp to the wheels which would equate to about 500 bhp (350 SAE Net Hp) rating. The top speed recorded for a factory produced 454 Chevelle, in 1970, perfectly tuned and equipped with the automatic transmission is 106.76 mph (171.81 km/h). There were 4,475 Chevelle units leave the assembly line in 1970 with the LS6 engine, although only 137 units are officially accounted for and currently on the National Chevelle LS6 registry.
The 1965 Buick Skylark power option is called the Grand Sport with the largest engine in the GM arsenal allowed for intermediate-sized cars. The engine size allowed at the time was 400 cubic inches, but the Grand Sport actually had a 401-cubic-inch (6.57L) V8, which produced 325 hp (242 kW) and had the moniker “nailhead.” The option was a big hit in 1965 and ’66.
In 1967, the Grand Sport became a new model and along with it came the GS 340 and the GS California. All three are available in a two-door hard-top or coupe with upscale badging and trim. The 340-cubic-inch (5.57L) engine produced 260 hp (194 kW). The power option was a newly designed 400-cubic-inch engine rated low at 340 hp, which kept insurance premiums down. The 1968 model came with a bit larger basic equipment 350-cubic-inch small-block (5.7L).
The 1968 and ’69 models came in a convertible and in a hard-top style, as well. They came equipped, if you liked, with a Rochester four-barrel on the intake of the 400-cubic-inch with the still-underrated horsepower placed at 340. The compression ratio on the stock engine was 10.25:1, which allowed it to run on regular or premium fuel.
The three-speed transmission, the basic option, complements the motor. You could have chosen the three-speed turbo Hydra-Matic 400 automatic transmission, possibly the finest transmission ever made, or a Hurst “dual-gate” shifter and linkage on the four-speed; both options mount in a console. The optional transmissions had duel exhaust pipes included in the package. The price was high compared to the competitions’ lesser cars, but in 1969 Buick stepped it up a notch with the “stage one option,” but this great car was not a big seller. The Grand Sport 350 outlasted the other two models, but the company shelved it in 1975 because of its high base price and replaced it with the Grand Sport 231.
The GS 455 in 1970 dropped the 400 in favor of a base 455-cubic-inch V8 putting out 350 hp (260 kW) at 2800 rpm. With the Stage 1 trim power option, the engine puts out 360 hp (260 kW) at the low 2800 rpm line.
All American engines were rated with a gross horsepower rating prior to the 1972 model year, but both engines are most likely rated lower than they actually could be due to insurance prices and existing regulations. With perfect timing and a carburetor tuned precisely, objective tests rated the 360 hp engine at 381.7 actual horsepower. This stage 1 option has a hot cam, higher compression, unique cylinder heads, with larger intake and exhaust valves. The automatic transmission was available with a crisper shift or a Muncie M-22 four speed. This car rated as faster than any of the Chrysler Hemis, and this has been an ongoing controversy over the years among muscle car buffs.
There was also a very rare stage 2 dealer option available, and there is little documentation available on this rare engine option, but it is a racing-equipped GS 455. Very few ever made it onto the streets.
The GSX Stage 1 was the high-performance offer starting in 1970, and it came with the 455 big-block as standard equipment. The only option offered is a four-barrel. The 1970 came in Saturn yellow and Apollo white, but in 1971, the car had six colors. The GSX came with a striking black lengthwise stripe outlined with red pinstriping over the rear spoiler.
There's a tachometer mounted on the hood with a black front spoiler, as well. The bucket seats, floor shifter, quick ratio steering, wide oval tires, front and rear sway bars were all included in the package. The options were standard or automatic transmissions.