10 May 2016

This is the difference between Small and Big Blocks

Mouse and Rat, Turbo-Fire and Turbo-Jet, Small Block and Big Block. While the application of electronic engine controls and forced induction may challenge the old saying, there is still truth to the cliché ‘there is no replacement for displacement’. The 1960s saw manufacturers building engines for their product lines that generally topped out near 450 to 460 cubic inches, but not necessarily divided into different engine families.

As far as differentiating engine series, Chevrolet could be viewed as the most successful OEM. What is now known as the Chevy small-block ranged from the first 265-ci in 1955, all the way to 400-ci by 1970. But it is largely recognized for its ubiquitous 350-ci variant, which seems to have been produced countlessly. Chevy production big-blocks range from 348-ci to 454-ci in passenger cars, but have also been offered in other displacements for different applications. However, the difference between the two lines is distinct; stand the two blocks next to each other and telling which offers more capacity is easy.

Chevrolet introduced their first post-war, mass produced V-8 with 265-ci in both the Bel-Air and Corvette producing 162hp and 195hp, respectively. While the Turbo-Fire small-block’s development would continue, every subsequent small-block shares commonalties; one of which is bore spacing, or distance between the center of one cylinder bore and the next, measuring 4.4 inches. When comparing a small-block against a big-block, this is one of the design parameters that will ultimately influence the block’s external size and the total volume it can contain. If you want more volume (without making the block taller), the bores’ radii must be larger and thus farther apart meaning the cylinder case must be longer.

The basic design that is the small Chevy underwent several generations, with the currently produced LS-series considered the fifth. The first, however, was in production from ‘55 through 2003.

The big-block Chevrolet was introduced in 1958 and was primarily designed for larger passenger cars and light trucks. It fulfilled the need for an engine that produced more torque as cars became heavier. Less than a decade later it underwent noticeable changes, but was initially launched as the Turbo-Thrust V-8 and featured 348-ci displacement. The big-block first offered 250 hp with a single four-barrel carburetor, and the optional Super Turbo-Thrust produced 280 hp using three two-barrel carbs. Additionally, the combustion chambers were in the block. The Super Turbo-Thrust, with its uniquely shaped rocker covers, eventually grew to 409-ci (although an aluminum 427-ci V-8 was an RPO option for racers in 1963, too) before being replaced by the more common Mark IV series engines.

The new Mark IV series, initially offered in mid-1965 was built around the same 4.84 inch bore spacing as the 348-ci. However, its combustion chamber was moved into the cylinder head, and the intake and exhaust valve layouts were modified. This engine was offered displacing 396-ci, 427-ci and 454-ci during the late ‘60s and early ‘70s, and went through several iterations incorporating improvements and new technology.

Pontiac’s engine program took a different route however as they do not have a small- and big- block, but one engine architecture. Introduced in 1955, like Chevy’s small-block, the “Strato-Streak” displaced 287-ci and made 180 hp with a two-barrel carburetor, and 200 hp with a four-barrel carburetor. Over time, this engine grew all the way up to 455ci by the late 1960s without any changes to its external dimensions. Thus, Pontiac only has a single V-8 block as it was more than capable of competing with Chevrolet’s entire lineup.

In the same period, Ford’s most common offerings were the long-lived Windsor series of small-blocks, the mid-range FE series and the big 385 series. Introduced for the 1962 model year, the Windsor started at 221-ci for the intermediate sized cars in Ford’s lineup and eventually grew to a 351-ci displacement over its 39-year life. Ford’s smallest V-8 through this era, the Windor’s displacement varied by modifying the design’s deck height.

The FE engines topped out at 428-ci after being introduced in 1958 as small as 332-ci. This range contains the iconic Cobra Jets and Ford’s SOHC motor. It underwent notable changes during its life but its design falls between the small ford Windsor and the later 385 series. However, the bare block appears larger than the Windsor due to its deep skirt design.

Starting in 1968 Ford began offering, what is considered by many, their big block: The 385 series engines offered in 370-ci, 429-ci and 460-ci variants. The 460-ci variant was used in trucks and other heavy-duty applications into the late ‘90s.

Chrysler offered two different main lines of engines during this time. The LA was an evolution of their earlier poly-spherical A-series engines, which were both built on a 4.460 inch bore space. It started out in 1964 displacing 273-ci and grew as large as 360-ci by 1971. This engine saw a relatively long life, and evolved into Chrysler’s Magnum line, which was built into the 2000.

The RB-series was Chrysler’s larger line introduced in 1959 as a change to their B-series engines. While the change in the A line was designed to improve and lighten (L(ight) A series), B-series changes were centered around increasing the engine’s stroke longer and hence made the engine taller. The RB series started with a 383-ci displacement and grew into the 440-ci.

You cannot talk about Chrysler small and big blocks without discussing the Hemi, however. While it shares some dimensions with the 426 Wedge motors offered in the RB line, it is its own animal, and you would not say that someone has a big-block Chrysler Hemi, it’s just the Hemi. Built on the same 4.800 inch bore spacing as the Wedge, its massive cylinder heads and tall 10.72 inch deck height make it hard to fit in many engine bays, but allowed it to earn its “elephant” nickname for more than one reason.

So, what matters more when calling an engine a small- or big-block, really depends on whether the engine in question had a dimensional juxtaposition. Cadillac offered a 500-ci engine that was nearly the same size, dimensionally, as a small-block Chevrolet, but that does not make it a small-block Cadillac. And while this only a brief overlook at many engines manufactured over many years, it’s important to remember that in most cases accuracy depends on what manufacturers called the engines, not conventional perception.

0 Reader Comments

Join the Discussion