The Novak Guide to
The Chevrolet Big Block V8 Engine
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| The Chevrolet Big Block V8 |
In its most familiar and long-running format, the Chevrolet Big Block was Introduced in 1965 as a 396 c.i. powerplant and from that time forth, it has earned its own place in automotive history as one of the most well known tour-de-brute-force engines on the market.
Known for knock-out power and high revving capabilities, the Big Block V8 is respected worldwide as one of the most impressive engines of our era. There are many larger Jeeps into which these engines can be converted.
A Dose of Chevrolet Engine History
As early as Chevrolets were on the road, they were developing a reputation as cars with an edge on performance. Chevy’s first V8 was actually introduced in 1917. It was a 90 degree, overhead valve engine. It was produced for only two years - as Chevy got into four and six-cylinder power instead for the “smaller” cars they were then producing.
Cadillac probably started the horsepower war when it introduced its new V8 in 1949. However, Chevrolet would soon bring it to the popular level with its historic Small Block V8 in 1955.
| The Engine "Swapping" Phenomenon In the fifties & sixties, the stage was set like this: people had Jeeps they loved, which had engines they did not. Simple popular interest soon propelled the V8 into the forefront of a burgeoning hobby of “engine swapping.” Jeeps were amongst the first recipients of these motors. One writer on this topic in the early 1970s estimated that there were upwards of 60,000 Jeeps that had been swapped to Chevy or Buick power. We don't know where he got his numbers, but it is hardly inconceivable. In thousands of conversations by phone and mail, we regularly and invariably get the question, “Why Chevy power? Why do you not push Ford and Mopar conversions as much as GM swaps?” GM swaps are, very simply, what so many people are asking for, and in increasing numbers. Since the late fifties, Chevrolet power has found its way into nearly any vehicle with wheels. Everything from MG’s, to Jeeps to motorcycles. So much so that it is even understood on the popular level, as evidenced by an episode of the television show Home Improvement, where Tim Allen proposes putting a Chevy 350 into the vacuum cleaner. GM swaps promote themselves because they are so good for so many reasons. Take it or leave it, most swappers will get more value for their money and time with a GM swap because they are well documented in literature, well supported in parts and they often make very good mechanical sense. |
W Series Big Blocks
An important precursor to the Big Block was the 1958 W Series engine. These motors ranged from 348 to 409 to 427 c.i.d., developing up through a [factory claimed] 430+ horsepower and 435 ft. lbs. of torque.
Mark IV Big Blocks
Rumors swirled and significant redesigns ocurred and in 1965, Chevrolet released its new Big Block as a 396 in its flagship Corvette model. 427 and 454 versions followed afterwards. Power probably peaked at 650 hp in special GM tune at the top of the muscle era. Race and drag applications go beyond that.
The engine was produced for many Chevy cars through 1976 and the Corvette through 1974. They saw uninterrupted service in many models of Chevy / GM trucks. The motors did begin to see detuning in the fuel-crunched 70's and tangling emissions controls certainly did't help the situation. The "Mark V" Big Block was the last of the GM engines to hang on to carburation, and was so equipped through 1995.
OBD-II and the Current Era
The 454 Big Block was reappointed with fuel-injection in 1996 and successfully met On Board Diagnostics level II standardization and efficiency requirements and was dubbed as the 7400 Vortec.
2001 saw the introduction of a stroked version of its 454, with displacement up to 8100cc (494 c.i.d). The block and heads are still of cast iron.
On the above topic; through the years, GM discovered what outside performance circles have previously known; that its Small Block V8's (thanks to tuning at GM and on the aftermarket) could develop equivalent amounts of power to many factory tuned Big Block V8 motors. Given the engine weight and its associated cost of materials, manufacturing expense and political/customer expenses in fuel economy, GM morphed its new Generation III Small Block engines into high-output (gloriously high, in some cases) versions ranging from 4.8L to 6.2L versions.
Though there are factory Small Blocks that can acheive the 340 hp and 455 ft. lbs. of torque, the Big Block can do so continuously under heavy-duty situations over longer periods. As such, the Big Block motors have been relegated to the bigger, medium duty trucks, especially in light of the diesel motors now available in many GM truck applications.
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| The Chevy V8 is sometimes called the "Rat" motor, a take-off from the popular term "Mouse" motor, given to the Small Block by its enthusiasts. |
Big Blocks & Jeeps
These V8's can make for very respectable sources of motivation in full-size trucks delegated to heavy work and tow duties. Big Blocks have been installed into a variety of Jeeps, especially the wide-frame variety such as the Full Size Jeeps and YJ Wranglers. Big Blocks have little place in most narrow-frame Jeeps (CJs, TJ Wranglers, XJ / MJ Cherokees, etc). The installer should consider the weight, economy and power factors in planning out a Big Block swap in any Jeep. With so many power options available for the GM/Chevy Small Block V8, there are few situations where it would not be an overall superior choice to the Big Block.
Transmission Compatibility
Some popular transmission choices with these motors in Jeeps include:
Manuals, non-native upgrades
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| SM420 (*) | SM465 (*) | Ford T18 (**) | Ford NP435 (**) | ||
Manuals, Jeep native
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| T90 | T150 | T176 | AX15 | NV3550 | ||
Automatics, non-native upgrades
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| TH350 | TH400 | TH700R4 / Early 4L60-E | 4L60-E (later) |
Electronic transmissions are typically paired or pulled with the same year of engine and PCM. PCM controlled engines getting a non-electronic automatic transmission should have their PCM programmed as if paired with a manual transmission. |
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Summary
Of course, the mechanical history of the Chevrolet V8 motor is much richer than this synopsis, and we do recommend more research and reading for the enthusiast. However, as there are some important mechanical details that are pertinent to Chevy Big Block swaps in Jeeps, we have created some valuable interchange information.
Generation III
GM's Generation III Small Block engines are such an advance, we've created a separate section for them.
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| The glorious re-release of the 427 in 2008. The first one was auctioned off at Barrett-Jackson. 427 hand-built models are to be made. GM's description includes the glorious phrase, "The 427 lucky owners of this commemorative monster can expect a grossly underrated 430 horsepower and 444 lb-ft of torque." |
Sources:
-The Novak Knowledge Base (and its 40 years of customer input)
-GM Powertrain
-GM Performance Parts
-Wikipedia