Chevy Small-Block History 1970-1979
Article by Mark Trotta
The decade of the 1970's brought four new variants of the popular small-block Chevy V8. It was a time when engine horsepower ratings would fall to new lows, but then rebound with more power and less pollutants.
1970 - Starting off the new decade, the 350 small-block was offered in 250, 270, 300, 350, and 360 horsepower variants, as well as a new 370 horsepower version.
350 LT1 Engine
Designed by Zora-Arkus Duntov, the LT1 350 featured large-valve cylinder heads and a solid-lifter, high-lift camshaft. The lower end featured four-bolt main caps, forged crankshaft and connecting rods, with 11:1 compression forged pistons.
An aluminum high-rise dual-plane manifold was topped with an 800-cfm four-barrel carburetor. Ignition system was GM's latest transistorized Delco unit.
Offered with a four-speed manual transmission only, output was 370-horsepower at 6,000 rpm with 380 pound-feet of torque at 4,000 rpm. Lots of cam overlap gave the LT1 motor a distinctive lumpy idle.
Available in the Corvette and Camaro Z28 from 1970 to 1972, many consider the LT1 350 the ultimate Gen One small-block. A Corvette so equipped was nearly as quick as a big-block Corvette, and with less weight gave much better agility and handling.
400 Small-Block (1970-1981)
With a 4.120-inch bore and a 3.750-inch stroke, the 400 small-block gave the displacement of a big-block, but kept the same external size and weight of a small-block engine. First-year 400 small-blocks were available in 265 and 330 horsepower versions.
The cylinders of the 400 were "siamesed" and required steam holes in the block, cylinder heads, and head gaskets. Therefore, these parts did not interchange with other SBC's. Whereas other small blocks are internally balanced, the 400 SB was externally balanced, requiring the use of a different flywheel.
Fitted from the factory with mild cam and modest induction, the 400 was never intended as a high-performance engine. Still, hot rodders found that it's abundant torque made the basis for a great street motor. It was the largest displacement small-block that Chevy produced.
1971 - Compression ratios on all GM engines were lowered to help them run on unleaded fuel. On the LT1 350, a decrease from 11:1 to 9.0:1 lowered output from 360 to 330 horsepower.
Gross vs Net Horsepower Ratings
Prior to 1972, published horsepower ratings were expressed as SAE (Society of Automotive Engineers) Gross. These figures reflected an engine's output without power-robbing accessories, such as cooling fan, exhaust system, and alternator. Starting in 1971 and going industry-wide in 1972, engine output was expressed as SAE Net, with horsepower measured at the rear wheel. The result was lower advertised horsepower ratings.
OPEC Oil Embargo
The 1973 U.S. Oil Crisis made the gas-thirsty Muscle Cars and Pony Cars fall further in the marketplace. The OPEC oil embargo deepened in 1974, and in an effort to conserve fuel, President Nixon signed legislation making 55-mph the national top speed limit.
L82 Small-Block (1973-1980)
1973 - The LT1 engine was dropped, and in it's place was the L82, which featured four-bolt mains, a forged steel crank, and aluminum intake manifold. Power output was 250 horsepower.
1974 - With emission regulations and unleaded gas already bringing about lower compression ratios, performance motors and the muscle car era in general slowly began fading away. The Corvette's base 350ci engine (L48) produced just 195 horsepower, with the optional L82 350 rated at 250 horsepower.
262 Small-Block (1975-1976)
The new for 1975 Chevy Monza was originally envisioned with Rotary engine power. Instead, a 140-cid aluminum four cylinder was the base motor, with an optional 262-cid small-block V8. With a bore and stroke ratio of 3.67 x 3.10", the 262 has the distinction of being the smallest small-block Chevy ever produced. Available in 1975-1976 Chevy Monza's and 1975 Nova's, power output was 110 horsepower.
1975 - The base Corvette engine (L48) bottomed out at 165 horsepower, with the optional L82 dropping to 205 horsepower. Even with these low figures, the 1975 Corvette was still one of the fastest cars available at the time.
1976 - After bottoming out in 1975, horsepower ratings began slowly rising. At 8.5:1 compression ratio, the base Corvette L48 engine produced 180 horsepower. The optional L82 motor had a slightly higher 9.0:1 CR and put out 210 horsepower.
305 Small-Block (1976-2002)
Looking to reduce emissions but still keep the torque of a V8, GM engineers developed the 305 small-block. The engine shared the same 3.480" stroke of the 350, but featured a smaller 3.736" cylinder bore and a lighter crankshaft. By sharing many components with existing motors, production costs were kept down.
The 305 small-block not only powered Chevy passenger cars and light-duty trucks, it was also seen in many other GM vehicles, including the Buick Regal, Pontiac Bonneville, Firebird, and Grand Prix, the rear wheel drive Oldsmobile Cutlass, and others.
1977 - Chevy engine paint color was changed from orange to blue, although some early production 1977 models were built with the orange-painted engines. Dipsticks were moved from the drivers side to the passenger side of the car.
267 Small Block (1979-1982)
Available in the Malibu and Monte Carlo, the 267 featured a 3.50 x 3.48 bore and stroke, which happened to be the same bore and stroke as the new 200cid V6. This allowed interchangabilty of many internal parts.
1979 - Top of the line small block for 1979 was the carbureted L82 350 producing 220 horsepower. Factory-installed low restriction exhaust systems helped increase power output.
Hot Rods, Jeeps, And Kit Cars
Because of their relatively light weight and compact size, SBC V8's are often seen in other-than-Chevy cars and trucks. They became popular engine swap choices for CJ Jeeps, hot rods, T-Buckets, and various kit cars.
Read: Chevy Small-Block History 1955-1969
Read: Classic Car Emissions Systems
Classic Car Engine Oil
The 10W-30 oil your car left the factory with is not the same 10W-30 that you buy today. There are more flat-tappet hydraulic cam failures than ever before, brought about by inferior foreign lifters as well as the removal of ZDDP additives from motor oils.
Read: Best Oil For Classic Cars