Chevrolet Small-Block engine: Encyclopedia II - Chevrolet Small-Block engine - Early Small Blocks

Chevrolet Small-Block engine - Early Small Blocks

Most current GM small-block V8s (the LT and LS series) trace their lineage to the 1955 265 in³ V8 developed for the Corvette. Displacement and power eventually reached 327 in³ and 509 hp (in prototypes) before the Corvette switched to Chevrolet big-block power. But the small-block lived on, settling in at 350 in³ for decades of performance.

Chevrolet Small-Block engine - 265

The 265 in³ (4.3 L) V8 was the first Chevrolet small block. Designed by Ed Cole's group at Chevrolet, it filled the power gap in the 1955 Corvette lineup, producing an impressive 195 hp (145 kW). The little engine went from drawings to production in just 15 weeks. Besides its compact dimensions, the small-block was known for its novel green-sand foundry construction process.

Dimensions were oversquare - 3.75 in (95 mm) bore and 3 in (76 mm) stroke. The small-block's 4.4 in (111.8 mm) bore spacing would continue in use for decades. It was a pushrod cast-iron engine with solid lifters and a 4-barrel Rochester carburetor. A passenger car version produced 162 hp. The first two production years of this motor had no provision for oil filtration, and as such the engine is undesirable to all but period collectors.

The 1956 Corvette introduced three versions of this engine - 210 hp (157 kW), 225 hp (168 kW) with twin 4-barrel carbs, and 240 hp (179 kW) with a high-lift cam.

• 1954, 1956 Chevrolet Corvette
• 1955 Chevrolet, 165 hp (2-barrel) and 195 hp (4-barrel)

Chevrolet Small-Block engine - 283

The 283 in³ (4.6 L) V8 was introduced in 1957. It was a version of the 265 in³ (4.3 L) bored-out to 3.87 in (98 mm). There were five different versions ranging from 220 hp to 283 hp (164 kW to 211 kW) depending on whether a single carb, twin carbs, or fuel injection was used. Power was up a bit each year for 1958, 1959, and 1960.

The 1957 engine featured Ramjet mechanical fuel injection, allowing the engine to produce 1 horsepower per cubic inch, an impressive feat at the time. For 1961, an amazing 315 hp was available from this unit.

• 1957-1962 Chevrolet Corvette

Chevrolet Small-Block engine - 302

Chevrolet produced a special 302 in³ (4.9 L) engine for Trans Am racing. It was the product of placing the 3-inch stroke crankshaft from a 283 into a 4-inch bore 327 block. This engine was only used in the first-generation Camaro Z28. Conservatively rated at 290 hp (216 kW), actual output was at least 320 hp (239 kW). This block is one of 3 displacements that underwent a transformation for the 1968/1969 period when the main bearing size was increased from 2.30 inches to 2.45 inches.

Chevrolet Small-Block engine - 307

A 307 in³ (5.0 L) 307 version was produced from 1968 through 1973. Engine bore was 3.875 in (98.4 mm).

The 307 replaced the 283 in Chevrolet cars and produced 200 hp (149 kW) SAE gross in the 1960s. The later emissions-modified versions produced just 115 hp (86 kW) SAE net, giving the engine one of the lowest power-per-displacement ratings of all time. Chevrolet never produced a high-performance version of this motor.

The 307 was also unique in the fact that its casting alloy had a very low nickel content making it relatively soft. Due to this fact, this engine has low value among rebuilders because of reduced longevity.

Chevrolet Small-Block engine - 327

The 327 in³ (5.4 L) V8, introduced in 1962, was bored and stroked to 4 in (102 mm) by 3.25 in. Power ranged from 250 hp to 375 hp (186 kW to 280 kW) depending on the choice of carburetor or fuel injection. The L76 version produced 340 hp (254 kW) and 344 ft·lb (466 N·m), while the L84 was the top performer with 360 hp (268 kW) and 352 ft·lb (477 N·m) with solid lifters, a special cam, and Ram-Jet fuel injection. The 1966 L79 was the highest-performance that year 327 at 350 hp (261 kW) and 360 ft·lb (477 N·m). * 1963-1968 Chevrolet Corvette. This block is one of 3 displacements that underwent a major change in 1968/1969 when the main bearing size was increased from 2.30 inches to 2.45 inches.

Chevrolet Small-Block engine - 400

A 400 in³ small-block was introduced in 1970 and produced for 10 years. It had a 4.125 inch bore and a 3.75 inch stroke. Initial output was 240 hp. While popular with circle-track racers, the engine was prone to cooling troubles if cylinder heads from other blocks were fitted without proper modifications. The 400 produced a lot of torque at low RPMs compared to the other displacements and was used primarily in pickup trucks and the large B-cars (Caprice/Impala) but also found use in Vans which could not take a big-block motor. The 400 was eventually discontinued due to its inability to meet EPA emission regulations in place in the early 1980's.

The 400 was unique compared to all other displacements for 3 reasons:

• Due to the siamesing of the cylinder bores in the casting - there was no space between adjacent cylinder liners - this block was rather rigid and not prone to the cylinder bore flexing of the other displacements.
• This block used a much larger 2.65 inch main bearing assuring that crankshafts from all other blocks would not fit without special oversize bearings.
• This is the only small-block that used a 5.56 inch long connecting rod compared to the 5.7 inch connecting rod in all other displacements.

While Chevrolet never produced a factory performance version of the 400, it is highly sought out among racers who participate in the very popular 406 racing class - so named for the displacement created by a minor overbore. 400 blocks are nearly impossible to find as salvage today and as such the racing market is fed by 3rd party manufacturers who offer improved versions of the block.

Adapted from the Wikipedia article "Early Small Blocks", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki