Chevy Small-Block History (1955-1969)
Article by Mark Trotta
All classic V8 engines had performance potential, but early Chevy V8's 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 small block V8's produced from 1955 until 2003 are referred to as Generation One (Gen One) engines. This article covers production years 1955 through 1969.
First Chevy V8
First, let's get a bit of automotive trivia out of the way. Chevy's first V8 was not the 265 cubic-inch V8 introduced in 1955. Their first V8 was a 288 cubic-inch overhead-valve engine featuring a partially exposed valvetrain and nickel-plated valve covers. It was installed in the D-Series Chevrolet and built in 1917 and 1918 only. With a horsepower rating of 36, neither the motor nor the D-Series were very popular.
265 Small-Block (1955-1957)
In late 1954, Chevy introduced the "Turbo-Fire" V8, available in 1955 Chevy cars and light-duty trucks. A piston bore of 3.75" and relatively short stroke length of 3.00" (times 8) gave a displacement of 265 cubic-inches. The little V8 didn't actually get it's "small-block" nickname until Chevy's big-block arrived in 1965.
The cylinder heads on first-year small blocks were fitted with 1.72" intake valves and 1.50" exhaust valves. With an 8.00:1 compression ratio and a two-barrel carburetor, the Turbo-Fire V8 produced 162-horsepower.
The 265 Chevy V8 was an immediate success. Soon after, a second, higher-output version 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. With a Duntov-designed camshaft and some minor tuning, output rose 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: SBC 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 Small-Block (1957-1967)
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 at 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 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.
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.
Read: Best Oil For Classic Cars
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 continued to be available on Corvettes until 1965.
327 Small-Block (1962-1969)
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".
Chevy II V8
In 1964, a factory-installed small-block was available in the compact 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. These cars certainly surprised quite a few unsuspecting street racers in their time.
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, 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, the 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.
350 Small-Block (1967-2003)
1967 - An increase of piston stroke from 3.25" to 3.48" brought small-block Chevy displacement to 350 cubic inches. The crankshaft main-journal diameter increased from 2.30" of the earlier blocks to 2.45", and rod-journal size increased from 2.00" to 2.10". The connecting rods were now stronger and heavier, having 3/8" diameter cap-bolts versus the previous journal 11/32" diameter.
The 350 small-block debuted in the 1967 Camaro and was offered in other Chevy cars and light-duty trucks the following year.
Read: 1967-1968 Camaro History
Crank Journal Diameter
In 1968, the 327 small-block was upgraded to the larger diameter crankshaft of the 350. Both 327 and 350 small blocks were produced in 1967, 1968, and 1969.
Read: Small-Block Chevy Build
307 Small-Block (1968-1973)
1968 - To give more power to the increasingly heavier cars while also help new emission standards, the 283 small block was replaced by a longer stroke 307 displacement. The crankshaft was sourced from the 327 (3.25" stroke) and the bore was the same as the 283 (3.875"). The cylinder heads had a smaller quench area to help emission ratings.
302 Small-Block (1967-1969)
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).
The 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.
Introduced in December of 1966, the 302 engine came with the Z-28 option on 1967 Camaro models. Performance parts 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. Early 302 small blocks were equipped with a forged-steel crankshaft and forged pistons. Compression ratio was 11.0:1.
1969 302 Small-Block
Originally based on the 327 block, the 302 motor was now based on the 350 block. The 4.00-inch bore and 3.00-inch stroke remained the same. By having larger main journals and four-bolt main caps, they were slightly stronger than the 327-based 302 motors.
The 302 Chevy small-block was purposely under-rated by the factory at 290 horsepower. Actual output was closer to 375 horsepower.
Read: Chevy Small-Block History 1970-1979
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