Chevy Small-Block History (First Generation)
Article by Mark Trotta
All classic V8 engines had performance potential, but early Chevy V8s had more performance potential right out of the box. This was largely due to it's already good breathing characteristics, coupled with the availability of good factory and aftermarket performance parts.
Chevy's First V8
Let's get a bit of automotive trivia out of the way. Chevy produced their first V8 in 1917. Called the Series D, it was an overhead-valve engine featuring an exposed valvetrain and nickel-plated valve covers. Some 36 years later, a completely new overhead-valve V8 arrived.
265 Chevy Small-Block
In late 1954, Chevy introduced the "Turbo-Fire" V8, or what we refer to as the small-block Chevy. The little motor didn't actually get it's "small-block" nickname until Chevy's big-block arrived in 1965.
With a piston bore of 3.75" and relatively short stroke length of 3.00", displacement was 265 cubic inches. Cylinder heads were fitted with 1.72" intake valves and 1.50" exhaust valves. With an 8.00:1 compression ratio and two-barrel carburetor, the Turbo-Fire produced 162-horsepower.
The Chevy small-block was an immediate success. Soon after, a second, higher-output engine was offered. With the addition of a four-barrel carb and some minor tweaking, power output increased to 180 horsepower.
Zora Arkus Duntov
When Zora Arkus Duntov was assigned to the Corvette in 1955, he was determined to upgrade it's performance and handling. A Duntov-designed camshaft, along with some minor tuning, increased small-block output to 195 horsepower. That was 30 horsepower more than the standard 265ci engine.
1956 Chevy Small-Block
First-year small-blocks did not have an oil filter nor a provision for one. An external filter canister, mounted atop the thermostat housing, was optional. Beginning in 1956, small-blocks were machined to include a block-mounted cartridge oil filter.
The 1956 model year started with two versions of the 265ci motor. There was the standard two-barrel motor (165 hp), and a Rochester four-barrel version (210 hp). High-lift cams were soon introduced to capitalize on the free-flowing characteristics of the motor.
In mid-year, Chevrolet introduced the 265 "Power-Pack" engine. This option included dual WCFB Carter four-barrels on an aluminum intake manifold and a mechanical lifter camshaft. With a compression ratio of 9.25:1, the little 265 was now pushing 225 horsepower.
A second dual-quad motor, producing 240 horsepower, was offered in the Corvette only. This was achieved by raising engine compression (9.25:1 to 10.3:1) and installing a new high-lift camshaft. The Duntov-designed cam, part #3734077, was a popular item at the Chevy parts counter.
Read: Camshaft Selection Guide
Another new camshaft featured the same duration as the 077 cam, but lobe lift was reduced slightly. The new cam's part number ended with 097, but is more commonly known as the 'Duntov' cam. This was the camshaft Chevrolet used in all solid-lifter small-blocks from 1957 through 1963.
Valve Cover Bolt Pattern
The first two years of Chevy small blocks had a slightly different valve cover bolt pattern than all other first-generation (1957-1985) engines.
Note that the two upper bolt holes (shown on right cover) are slightly closer together than the bottom two bolt holes (left cover).
283 Chevy Small-Block
Two years after its introduction, the piston bore of the 265 was increased from 3.75" to 3.875" Keeping the same 3.00" stroke, engine displacement was now 283 cubic-inches.
Early 283 motors would use 265 block castings, but it was found that the cylinder walls were too thin to handle the larger displacement. This led to overheating issues on early 283 blocks. A recasting of the block gave thicker cylinder walls and side motor-mount bosses.
After the 283 small-block was released, the 265ci V8 was only offered in a two-barrel version.
1957 Chevy Engine Options
In addition to a six-cylinder option, there were no less than seven V8 options for the 1957 Chevy. The 283 was available with the standard two-barrel, optional four-barrel (220 hp), dual quads (245/270 hp), or new mechanical fuel-injection.
Read More: 1957 Chevy History/Engine Options
Ramjet Fuel Injection (1957-1965)
The Rochester-built mechanical fuel injection system (also optional on the 1957 Pontiac Bonneville), was available in two power ratings. Most Ramjet fuel-injected motors were the 250 horsepower, smooth-idle 283, which often powered four-door Bel Airs loaded with optional luxury equipment.
283 Cubic-Inches, 283 Horsepower
The higher output Ramjet fuel injection, producing 283 horsepower, allowed the division to claim "one horsepower per cubic inch". Although Chrysler had achieved this figure with its 1956 300B, Chevrolet capitalized on it, through racing wins and advertising.
1960 283 Ramjet
Raising compression to 11.0:1, fuel-injected 283 small-blocks were now producing 275/315 horsepower. In 1962, compression was raised to 11.25:1.
The Ramjet fuel injection system was complex for it's day and not popular with the general public. Most dealers didn't know how to work on them, and often replaced the system with a carburetor intake system. The Ramjet option was dropped on Chevy passenger cars after 1959, but would be available on Corvettes until 1965.
327 Chevy Small-Block
For 1962, the 283 small-block was bored to 4.00" and stroked to 3.25" making a displacement of 327 cubic-inches. Similar to the 265's fate, all 283 engines would be relegated to two-barrel-only configurations.
In 1963, Chevrolet began designating engines with letter/number codes. These most always started with the letter "L".
V8 Engine Swap
In 1964, a factory-installed small-block was available in the Chevy II. Before that, both dealers and enthusiasts alike were performing V8 conversions to the little car. With a Chevy II weighing about 2,500 pounds, a small V8 under the hood gave an excellent power to weight ratio. Small-block Chevy V8's began appearing in other makes and models, too.
in 1964, Chevrolet replaced the Duntov 097 cam with a newer version, known as the '30-30' camshaft. This was the cam that allowed the fuel-injected 327 to produce 365 horsepower, and with a compression bump to 11.25:1, it produced 375 horsepower.
Until the appearance of the 385 horsepower LS6 in 2001, the L84 was the most powerful naturally aspirated, single-cam small-block Chevrolet ever produced.
The L76 motor had a hydraulic cam and single four-barrel carb. With compression at 11.25:1 factory horsepower rating was 340. In 1964, engine output rose to 365 horsepower.
In 1965, Chevrolet released the L79, a 350-hp engine with a single four barrel. This engine had a Duntov solid-lifter cam, 11.0:1 forged pistons, forged steel crank and rods, and large 2.02 intake valves.
Displacement Increase To 350
An increase of piston stroke from 3.25" to 3.48" brought small-block Chevy displacement to 350 cubic inches. The 350ci small-block debuted in the 1967 Camaro and subsequently offered in other models the following year.
Both 327 and 350 small blocks were produced in 1967 and 1968.
Crank Journal Diameter
In 1968, the Chevy updated the small-block with a larger diameter crankshaft. The main-journal size was increased from 2.30" to 2.45". The rod-journal size was increased from a 2.00" diameter to a 2.10" diameter.
Read: Gen One Small-Block Chevy Build
The connecting rods were now stronger and heavier, having 3/8" diameter cap-bolts versus the smaller journal 11/32" diameter.
302 Chevy Small-Block
The 302 may be the least-known of Chevy's performance V8s, but never the less, it's a good one.
In late 1966, Chevy wanted their new Camaro pony car to compete in the Trans-Am racing series. Sanctioning rules limited engine displacement to 5.0 litres (305 cubic-inches).
Their solution was to place a 283 crankshaft (3.00-inch stroke) into a 327 block (4.00-inch bore) which made a short-stroke, high-revving, 302 cubic-inch motor. This was not a new idea, hot rodders had been doing this for years.
Read: 1967-1968 Chevrolet Camaro
Early Z-28 engines were equipped with a forged-steel crankshaft and forged pistons. Engine blocks had four bolt main caps to help handle the higher revving capacity.
Performance parts on the 302 small-block also included an aluminum high rise dual-plane intake manifold, 780-cfm 4-barrel Holley carburetor, large 2.02" intake valves with 1.60" exhaust valves, and a Duntov-designed solid-lifter camshaft. Compression ratio was 11.0:1.
1969 302 Small-Block
Originally based on the 327 block, the 4.00-inch bore and 3.00-inch stroke 302 motor was now based on the 350 block. These were slightly stronger than the earlier 302's by having the larger main journals and four-bolt main caps.
The 302 was purposely under-rated at 290 horsepower. Actual output was closer to 375 horsepower.
Available in the Corvette and Camaro Z28 from 1970 to 1972, many consider the LT1 350 the ultimate Gen One small-block. The bottom end featured four-bolt main caps, forged crankshaft and connecting rods, and 11.0:1 compression forged pistons. An aluminum high-rise dual-plane manifold was topped with an 800-cfm four-barrel carburetor.
Large-valve heads and a solid-lifter, high-lift camshaft with lots of overlap gave the LT1 a distinctive, lumpy idle. For 1970, engine output for the LT1 was factory rated at 370-horsepower at 6000 rpm, with 380 pound-feet of torque at 4000 rpm.
Emissions And Unleaded Gas
For the 1971 model year, compression ratios on all GM engines were lowered to help them run on unleaded fuel. A decrease from 11:1 to 9.0:1 put LT1 power output at 330 horsepower.
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. It would be more than a decade before Chevrolet, as well as other Automakers, to figure out how to produce cleaner-running engines without hurting performance.