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CATEGORIES (articles) > Engines > Chevy Engines > Chevy Big Blocks

Chevy Big Blocks

While most General Motors divisions simply created tall-deck versions of their V8 engines, Chevrolet created a new big-block design for large-displacement use. Cadillac also had a special big-block design.

Chevrolet's "W Series" engine was an overhead valve design with unique scalloped valve covers. Each bank of cylinders shared the same head design, which means the heads are interchangeable left-to-right.

Generation 1

The first big-block V8 family from Chevrolet was introduced in 1958 and produced through 1965. It was used in Chevrolet cars and trucks.

All first-generation engines used cast iron engine blocks and two-bolt main bearing caps. One change between the 348 and 409/427 was the location of the dipstick: It is on the driver's side on the former and opposite on the latter. The cylinder heads are all similar, apart from the larger valves used on the larger engines.

The first-generation big blocks had a dry weight (without oil or coolant) of approximately 665 lb (300 kg), depending on manifold and carburetion.


The first big-block, by GM's reckoning, was the 1958 "Turbo-Thrust" 348 in³ (5.7 L) originally intended for use in Chevrolet trucks, but also introduced in the larger, heavier 1958 passenger car line. Bore was 4.125 in (104.8 mm) and stroke was 3.25 in (82.5 mm). This engine was replaced by the 409 as Chevrolet's top engine in 1961 and went out of production for cars at the end of that year. It was produced through 1965 in large Chevrolet trucks.

The base Turbo-Thrust, with a four-barrel carburetor, produced 250 hp (186 kW). A special "Tri-Power" triple-two-barrel version, called the "Super Turbo-Thrust" produced 280 hp (209 kW). A "Special Turbo-Thrust" upped the output to 305 hp (227 kW) with a single large four-barrel. Mechanical lifters and the Tri-Power carb brought the "Special Super Turbo-Thrust" up to 315 hp (235 kW). For 1959, high-output versions of the top two engines were produced with 320 hp (239 kW) and 335 hp (250 kW) respectively. Even higher-output versions appeared the next year, at 340 hp (253 kW) and 350 hp (261 kW).


Model Name Features Power
1958 1961 Turbo-Thrust 4 barrel 250 hp (186 kW)
1958 1961 Super Turbo-Thrust "Tri-Power" 3x2 barrel 280 hp (209 kW)
1958 1961 Special Turbo-Thrust 4 barrel 305 hp (227 kW)
1958 1960 Special Super Turbo-Thrust "Tri-Power" 3x2 barrel 315 hp (235 kW)
1959 1960 Special Turbo-Thrust 4 barrel 320 hp (239 kW)
1959 1961 Special Super Turbo-Thrust "Tri-Power" 3x2 barrel 335 hp (250 kW)
1960 1961 Special Turbo-Thrust 4 barrel 340 hp (253 kW)
1960 1961 Special Super Turbo-Thrust "Tri-Power" 3x2 barrel 350 hp (261 kW)


A 409 in³ version was Chevrolet's top regular production engine from 1961 to 1964, with a choice of single- or dual-four-barrel carburetors. A 409hp version of the 409 came out in '62 equaling 1hp per cubic inch; a milestone in its day.

Output reached 425hp in '63 with the 2X4 setup. This included a solid lifter camshaft. This engine was underated for street purposes but put into production for drag racing purposes. Bore and stroke were both up from the 348 at 4.312 in (109.5 mm) by 3.50 in (88.9 mm). The engine was available through mid 1965. This engine was immortalized in the Beach Boys song titled "409".

427 (Z11)

A special 427 in³ (7.0 L) version of the 409, called the Z11, was used in the 1963 Chevrolet Impala Sports Coupe. Unlike the later second generation 427, it was a basic W-Series 409 engine, but with a longer 3.65 in (92.7 mm) stroke. An aluminum intake manifold and dual Carter AFB carbs fed a 13.5:1 compression ratio to produce an under-rated 430 hp (321 kW) and 435 ft·lbf (590 N·m). 50 Z11s were produced.

Generation 2

Development of the automobile big-block started with the Mystery Motor used in Chevrolet's 1963 Daytona 500 stock cars. The "secret" motor was released in mid 1965 as the Mark IV, and it was the dual-plane placement of the valves that was the key to its performance. The new "big-block" was also used by Chevrolet and GMC trucks. Production of this generation of engines ended in 1976.

The Rat Motor, as it was nicknamed (as opposed to the small-block "mouse" motor), was slightly heavier than the outgoing 409, with a dry weight of about 685 lb (310.7 kg), but had a stronger, more durable block. This engine was officially known as the "Turbo-Jet V8" from 1965-74.

396 and 402

The 396 in³ (6.5 L) V8 was introduced in the 1965 Corvette as the L78 option. It had larger bore and stroke at 4.094 in by 3.76 in (104 mm by 96 mm) than any previous small-block and produced an amazing 425 hp (317 kW) and 415 ft·lbf (563 N·m).

Introduced in 1970, the 402 in³ was a 396 in³ bored out by .030 in (0.8 mm). Despite the fact that it was 6 c.i. larger, Chevy continued marketing it under the popular "396" label in the smaller models, and as the "Turbo-Jet 400" in the full-size series.

  • 1965 Chevrolet Corvette
  • 1965-1972 Chevrolet Chevelle
  • 1967-1972 Chevrolet Camaro
  • 1968-1970 Chevrolet Nova
  • 1968-1972 Full-size models


L36 427 in a 1966 Chevrolet Corvette
L89 427 in a 1967 Chevrolet Corvette

The huge 427 in³ (7 L) V8 was introduced in 1966. Bore was up to 4.25 in, with power ratings varying widely. Not every engine combination was available in every car, and some engine options required other options (radio delete, manual transmission, etc).

The 1969 ZL1 is one of the best-remembered big-blocks. Originally for Can-Am racing, it had specifications nearly identical to the L88, but had an all-aluminum engine block that weighed 100 lb less than a similar iron block. The $4718 ZL1 option doubled the price of the 1969 Corvette. Just two production Corvettes and 69 production Camaros were made with this option.

Chevrolet gave all 427 engines except the ZL1 a torque rating of 460 ft·lbf (624 N·m).

Features Compression
1966 1969 L36 4-barrel 10.25:1 390 hp (291 kW)
1966 1966 L72 4-barrel + solid-lifters 11.00:1 425 hp (317 kW)
1967 1969 L68 3x2-barrel 11.00:1 400 hp (298 kW)
1967 1969 L71 3x2-barrel + solid-lifters 11.00:1 435 hp (324 kW)
1967 1969 L89 L71 + aluminum heads 11.00:1 435 hp (324 kW)
1967 1969 L88 L72 + aluminum heads 12.50:1 430 hp (321 kW)
1969 1969 ZL1 L88 + aluminum block 12.25:1 430 hp (321 kW)


  1. ^ Chevrolet actually advertised this engine as 450 hp (336 kW) for a short period of time. There is speculation if this engine actually put out 450 hp, or if this was a marketing mistake that was later corrected.
  2. ^ L88 had a 12.5:1 compression ratio with closed chamber heads except during the last half of 1969, when it had open chambered heads that yeilded 12.0:1
  3. ^ L88 was rated for 430 hp at 5,200 rpm. Actual red line was 6400 rpm however, resulting in over 500 hp. With free-flowing headers, it is rumored to have done over 550 hp.
  4. ^ Actual HP is not known for ZL1, but is accepted to have exceeded that of the L88

Some 427's were also used in GM full-size trucks, and the Blue Bird Corporation used the 427 in their All American and TC/2000 transit buses up until 1995. The later versions, made specifically for Blue Bird, were carburated.

  • 1966-1969 Chevrolet Impala
  • 1966-1969 Chevrolet Corvette
  • 1966-1969 Chevrolet Camaro
  • 1966-1969 Chevrolet Caprice


The big-block was expanded again for 1970 to 454 in³ (7.4 L) with a 4.251 in (108 mm) bore and 4 in (102 mm) stroke. The 1970 Corvette LS5 engine produced 390 hp (291 kW) and 500 ft·lbf (678 N·m), and the LS6 engine, which produced 450 hp (336 kW). It is generally accepted that the LS6 was underrated (as was the practice to keep insurance companies happy) and actually produced over 500 hp. A 465 hp (347 kW) and 490 ft·lbf (664 N·m) LS7 engine was produced, but was only available as a stand-alone engine.

Power began falling off after 1970, with the 1971 LS5 producing 365 hp (272 kW) and 465 ft·lbf (630 N·m), and the LS6 option coming in at 425 hp (317 kW) and 475 ft·lbf (644 N·m). Only the LS5 remained in 1972, when SAE net power ratings and the move torwards emission compliance resulted in to 270 hp (201 kW) and 390 ft·lbf (529 N·m). The 1973 LS4 produced 275 hp (205 kW) and 390 ft·lbf (529 N·m), with 5 hp (4 kW) and 10 ft·lbf (14 N·m) gone the following year. 1974 was the last year of the 454 in the Corvette.

GM continued to use the 7.4 L 454 in their truck line, introducing a new Vortec 7400 version in 1996.

  • 1970-1974 Chevrolet Corvette


A substantially-modified version of the 454 is sold today as the Vortec 8100.

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