The AMC V-8 is a great example of a domestic V-8 engine that has-except for aficionados-be
Everyone likes to dis America, until it's time for America to bail them out. This happens almost daily in the walk of global politics, but interestingly, it goes down with great frequency in the hot rodding scene as well. While foreign elitists love ripping on our primitive, big-inch, pushrod engines, they often replace their high-tech, high-winding, turbocharged, weenie-displacement slugs with red-blooded American lumps. Without the 427 Ford FE engine, the AC Cobra would've been just another turd of a British sports car. Likewise, you'll frequently find small-block Chevys in Porsches, Mazdas, BMWs, and Datsuns, but when is the last time you saw a Porsche, Mazda, BMW, or Datsun engine in a Chevy? Um, like never. The world didn't seem to mind, either, when the Allison V-1710-in its 1,700 ci, 12 cylinders, and 1,000 hp of glory-helped P51 Mustangs shoot down Nazis over the skies of Europe during World War II, saving humanity from a perpetual state of Oktoberfest and a global outbreak of smelly sauerkraut. OK, the Allison was a V-12 aircraft motor, but you get the point.
Mass-produced mainstream V-8s, embraced by both hot rodders and the average consumer alike, have endured the test of time by virtue of their overall excellence. The Chrysler LA-series small-block, Ford Windsor, and all four generations of Chevy small-blocks each offer a balance of horsepower, low mass, compact size, versatility, fuel mileage, modification potential, and low cost that reflect their universal appeal. Consequently, each of these platforms have powered everything from muscle cars to trucks to fullsize vans to 9-second drag machines to RVs. VTEC that, Mr. Baggypants. In the case of Hemis and big-block Chevys, these engines have set the gold standard for outrageous power and on-track dominance. With few exceptions, trying to hang with a max effort Hemi or Rat motor with anything other than a Hemi or Rat motor is a losing proposition, and it's been that way for 50 years.
Even so, there exists an elite cadre of production engines that few people outside of die-hard brand loyalists remember. It's not that they were poorly engineered heaps that had little to offer. More often than not, they boasted cutting-edge technological innovations and set performance benchmarks for their time, but were replaced by more cost-effective alternatives. With decades of R&D separating these motors from today's crop of engineering marvels, the horsepower figures of these relics of internal combustion aren't too impressive by modern standards. Nonetheless, judged against their contemporaries, they could more than hold their own. So without further delay, and further alienating the international community, here's a retrospective on some of the greatest engines that time forgot.
Oldsmobile Aluminum 215
With exception of the small-block Chevy, the all-aluminum Oldsmobile 215 and its Buick cousin are arguably the most prolific American V-8s of all time on the international stage. GM began experimenting with a lightweight aluminum V-8 design in the early '50s for use in Y-body Buicks, Oldsmobiles, and Pontiacs. Buick was given lead R&D responsibilities, but Oldsmobile developed its own unique variant which it introduced in 1961. This new engine platform featured a 3.500-inch bore, a 2.800-inch stroke, and a 4.240-inch bore spacing that contributed to its compact external dimensions. With an aluminum block and heads, the Olds 215 weighed just 320 pounds, making it one of the lightest production V-8s in the world. Many of the 215's trick design elements are still very impressive today, such as shaft-mount rocker arms, a 10.25:1 compression ratio, and the use of six head bolts per cylinder. Despite its modest displacement, the 215 produced 185 hp and 230 lb-ft of torque. However, that was just the beginning. In '62, Oldsmobile strapped a turbocharger to the 215, bumping output to 215 hp and 300 lb-ft. While modern turbo motors employ gasoline direct injection and advanced electronics to successfully combine such high-static compression ratios and boost, the 215 had a different hot rodding trick up its sleeve. To prevent detonation in a carbureted 10.25:1 engine pushing 5 psi of boost, Oldsmobile rigged up a water injection system to cool the intake charge. In the event that the water supply ran dry, a restrictor valve built into the induction tract helped limit boost. By some accounts, the Olds 215 was the first engine to offer a turbocharger from the factory. Unfortunately, the 215 was relatively expensive to produce, and GM opted to replace it with larger, iron-based V-8s throughout the BOP product line.
Even after the demise of the BOP 215 following the '63 model year, the Buick variant lived on overseas. Seeking a lightweight V-8 to use in its small British cars, the Rover Company purchased the tooling and manufacturing rights to the Buick 215 in 1965. Through the decades, Rover sold the revamped Buick 215 to small car builders, and as such, it has appeared in Land Rovers, Morgans, MGs, Triumphs, and TVRs. Furthermore, Mickey Thompson fielded a car powered by a Buick 215 at the '62 Indy 500, which was the first production block-based entry in over 15 years. Believe it or not, the British Brabhams Formula One team took things one step further by converting a destroked version of the 215 for an OHC valvetrain, and winning the championship in the '66 and '67 seasons.
Turbo 3.8L Buick V-6
The Buick V-6 tells a tale more reminiscent of a soap opera script than the documented history of a production engine. This powerplant was conceived from scraps, sold to the highest bidder, dumped in the trash, reacquired by its original owners, and then catapulted to the performance stratosphere. When GM brass decided that the all-aluminum 215 V-8 was too expensive to manufacture in 1962, Buick hacked off two cylinders, cast the block from iron, and created the 198ci Fireball V-6 as a lower-priced alternative. Since this engine retained the 215's 90-degree crankshaft instead of a 120-degree unit that's more common in V-6s, the motor suffered from a rough-running disposition. It was enlarged to 225 ci, and installed in '64-67 Skylarks and '64-67 Cutlasses. Buick then dropped the 225 in favor of Chevy inline-six engines, and sold the tooling to Kaiser-Jeep in 1967. Kaiser was eventually purchased by AMC, and stopped producing the 225 in favor of an AMC straight-six.
Once the oil crisis hit in 1973, GM started looking for more fuel-efficient alternatives to replace its big V-8s. As one possible solution, Buick engineers unearthed an old Fireball V-6 out of the junkyard, installed it in a '74 Apollo, and management was extremely pleased with the results. GM purchased the tooling for the old Fireball V-6 back from AMC, and it re-entered production by '74. The bore was increased to 3.800 inches for '75, which yielded 231 ci (3.8 liters) when paired with a 3.400-inch stroke. Although the 3.8L V-6 was designed more for fuel efficiency than power, Buick made things interesting by bolting a turbocharger to it, then dropping it in the '76 Indy 500 pace car. The turbo V-6-powered Buick Century was a huge hit, and solved the problem created by the prior year's 455-powered pace car, which couldn't accelerate hard enough on the straights.
The success of the pace car prompted Buick to begin installing turbo V-6s across its product line starting in '78. Initially, output was a modest 175 hp, but the introduction of sequential fuel injection boosted power to 200 in '84. The advent of intercooling in '86 increased output to 235 hp, and the '87 model year saw another 10hp increase. Over the years, the turbo V-6 was installed in the Buick Regal, LaSabre, Century, and Riviera, as well as the '80-81 Chevy Monte Carlo and '89 Pontiac Trans Am. By far, the most popular recipient of this powerplant was the Regal Grand National, making it an instant cult classic that could handily smoke V-8 F-bodies of the era. Stout short-blocks allowed cranking up the boost, and running 12-second e.t.'s in near-stock trim. The king of all production turbo Buicks was the '87 GNX, which produced 276 hp and 360 lb-ft of torque. In the running for the wildest nonproduction turbo Buick is the 4.1L V-6 used in the '83 Indy 500 Riviera pace car. Equipped with twin turbos, a forged rotating assembly, six-bolt-per-cylinder head castings and sequential fuel injection, this engine produced 410 hp, exactly twice as much as the Corvette that would be released the following year. As the contemporary new car market has once again started focusing more small-displacement engines using forced induction, the turbo Buick V-6 was clearly ahead of its time.
"...Buick engineers unearthed an old Fireball V-6 out of the junkyard, installed it in a '74 Apollo, and management was extremely pleased with the results."
This sharp-looking Ford Y-block was rescued by Ted Eaton from a 1950s school bus, and buil
Due to Ford's propensity for juggling its engine lineup by constantly introducing new platforms, even Blue Oval buffs have a hard time keeping all of them straight. While most hot rodders are familiar with Windsors, FEs, Clevelands, and 385-series big-blocks, few people realize the significance of the Y-block platform. Introduced in 1954, the Y-block is essentially the nexus between the legendary Ford flathead and every production V-8 built after it that used an OHV valvetrain. Although pushrod valve actuation is often ostracized by the general public these days, back in 1954 it was ground-breaking technology. The Y-block beat the small-block Chevy to market by a year, and as such, it was one of the first mass-produced passenger car V-8s to incorporate an OHV valvetrain architecture. The engine's deep-skirt design resembled a "Y," creating a very robust bottom end and earning it the Y-block moniker.
The Y-block was offered in 239, 256, 272, 292, and 312ci configurations. The original 239 was rated at 130 hp, a big jump over the 106hp flathead it replaced. To keep pace with the 265ci small-block Chevy that was unveiled in '55, Ford countered by boring and stroking the Y-block to 292 ci. The hottest version of the platform was the 312, introduced in '56. It boasted a four-barrel carb and 9.0:1 compression, producing a stout 235 hp. Many dealers offered the M260 engine kit as an option, which included a set of high-flow heads, a bigger cam, and dual four-barrel carbs that bumped output to 260 hp. The 312 was certainly a strong performer, but when the small-block Chevy was enlarged to 283 ci with a matching 283 hp in fuel-injected trim, Ford had to fend off the attack to remain competitive in NASCAR competition. It responded by strapping a McCulloch/Paxton supercharger to the 312, bumping performance to a cool 300 hp. This engine was so dominant that not only did it win 26 races to Chevy's 21 in the '57 NASCAR season, it also prompted the sanctioning body to ban it altogether. To ensure that enough supercharged 312s were built to meet homologation requirements, Ford installed it throughout its model lineup. This led to some interesting applications of this blown mill. It's not surprising that the supercharged 312 showed up in Thunderbirds, but it was also dropped into cars like the Fairlane, Skyliner, and Country sedan.
Despite its success, the Y-block V-8 was phased out by the mid '60s in favor of the FE in large car applications, and the Windsor in the small-car market. Downsides to the Y-block platform included poor top end oiling, and an odd cylinder head configuration in which pairs of intake ports were stacked on top of each other, impairing high-rpm airflow. Furthermore, the Y-block was small both externally and internally, and Ford was hesitant to push displacement beyond 312 ci. Even so, the Y-block V-8 often outperformed its small-block Chevy competition, and it has seen a resurgence in popularity as of late, thanks to the rat-rodding movement.
"...the Y-block V-8 often outperformed its small-block Chevy competition, and it has seen a resurgence in popularity as of late, thanks to the rat-rodding movement."
With the introduction of the C4 Corvette in '84, enthusiasts raved about the world-class handling provided by its solid chassis and all-aluminum suspension. Unfortunately, hitting the gas pedal served as a painful reminder that horsepower was just starting to recover from the doldrums of the smog era. Corvette Chief Engineer Dave McLellan's solution was building a 400hp version of Chevrolet's flagship with aspirations of making it the fastest production car in the world. Considering that the Corvette's L83 small-block produced a wheezy 205 hp, this was quite an ambitious plan to say the least. Chevy toyed with turbocharged six- and eight-cylinder prototype engines before settling in a naturally aspirated V-8. Right around the time the LT5 program was taking shape, GM acquired Lotus. Consequently, Chevy and Lotus engineers determined that the 400hp target could best be achieved with a DOHC, 32-valve V-8, and the LT5 engine program was born.
GM originally contemplated fitting DOHC cylinder heads onto the existing 350 small-block Chevy, but Lotus engineers insisted that a clean-sheet engine design would be ideal. The result was an engine based on an all-new aluminum block that shared little more than its 4.400-inch bore spacing with the small-block Chevy. The minimum thickness requirement of the cylinder liners resulted in a slightly reduced bore size of 3.900 inches compared to the Gen I small-block, which was combined with a 3.660-inch stroke. Speaking of liners, the LT5 block used aluminum sleeves instead of iron. To make this possible, the liners were coated with Nikasil to reduce friction, a common design feature of BMW and Ferrari engines of the era. The crank and rods were both forged, while the hypereutectic pistons squished out an 11.25:1 compression ratio. The short-block was fortified with iron main caps that used an integrated girdle assembly. Like the LS1 that would someday replace it, the LT5's oil pump was driven off the front of the crank.
Without question, the LT5's most impressive pieces of hardware were its multivalve cylinder heads. In addition to their four-valve-per-cylinder design, these heads were matched with a variable-stage intake manifold featuring two intake runners per intake port. The end product is three throttle bores, 16 intake runners, and 16 fuel injectors. At low rpm, a small 22mm bore throttle plate feeds air into the intake, then two additional 59mm bores open as engine speeds increase to maximize both airflow and charge velocity. Since the LT5 was designed before electronics were advanced enough to operate variable valve timing systems, it employed several design elements that net a similar effect. The two intake ports used for each cylinder were staggered in size, with the secondary ports measuring slightly larger than the primary ports. The lobe profiles on the intake camshafts were staggered as well, with more duration for the secondary valves and ports. As a result, the LT5 shut down the secondary ports using an auxiliary throttle plate integrated into the heads at low rpm to preserve port velocity and bottom-end torque, then opened them up top for high-rpm breathing. After final R&D was completed, GM enlisted Mercury Marine to manufacture the production LT5.
When the LT5 debuted in the '90 Corvette ZR1, it produced 375 hp and 370 lb-ft of torque. For the '93 model year, output increased to 405 hp and 385 lb-ft, thanks to cam timing changes and improved cylinder heads. As impressive as its technical specs were, enthusiasts complained that the LT5 was soft on torque at low rpm. This could easily be cured with today's variable valve timing technology, but the LT5's biggest problem was the LS1. Recognizing that they could achieve power figures similar to the LT5 in a smaller, lighter, and far less expensive engine package in the LS1, GM engineers bid farewell to the 32-valve wonder after the '95 model year. Despite its ignominious fate, the LT5 was one heck of a performer for its day.
"...the LT5's biggest problem was the LS1 ... GM engineers bid farewell to the 32-valve wonder after the '95 model year."
During the era when real grassroots hot rodders could still race at the Indy 500, renowned land speed racer Barney Navarro shocked the motorsports world when he clocked 150-mph qualifying laps with a six-cylinder engine in 1967. Due to chassis tuning issues, Navarro's car didn't make the final cut for the race, but his lap times still stand as the fastest ever posted by a six-banger. The engine in question was a 199ci AMC inline-six, the same putt-putt mill anyone could get in a Rambler or Gremlin. Navarro liked the idea of a six-cylinder crank supported by seven main bearing caps, and the engine's over-square 3.750x3.000-inch bore and stroke dimensions were appealing as well. With a built short-block and a custom turbo system dishing out 105 psi of boost, the little six produced 700 hp. That was with the stock cylinder head, block, and rocker arms. Even if they don't realize it, the few remaining Honda drag racers weren't the first ones to combine small-displacement inline engines with a ton of boost.
If there's an oddball in this group of great, forgotten engines, it's the Buick nailhead. If the flat 12-degree valve angle of the late-model LS7 impresses you, take the nailhead's zero-degree cylinder heads on for size. That's right, the nailhead's valves were positioned vertically over the combustion chambers. Furthermore, the nailhead used shaft-mount rockers that were positioned outboard of the valves, pivoting inward toward the intake manifold. The jury's out on whether this unique arrangement had any positive or adverse impact on performance, but it certainly looked strange. Bench racing aside, in reality flattening the valve angle without optimizing the intake port inlet location severely compromises airflow, and the Buick's induction path was convoluted for sure. The benefit was that it resulted in an extremely compact package that wasn't nearly as wide as its fellow V-8 contemporaries. Furthermore, nailheads boasted rugged forged cranks and rods-which when combined with its compact dimensions-explains their overwhelming popularity in roadsters during the late '50s.
The first-generation nailhead was built from '53 to '56, and was offered in 264 and 322ci configurations. The nailhead's small valves looked like nails, hence the name, and yielded high-velocity ports with conservative cross-sectional area. The result was a torquey engine that generated more than 1 lb-ft per cubic inch, which was outstanding for the era. The second-generation nailhead was produced from '57 to '66 in 364-, 401-, and 425ci configurations. From '64 to '66, the 425 was the top dog in the nailhead camp, kicking out 360 hp and 465 lb-ft of torque. It featured a 4.312-inch bore, a 3.640-inch stroke, 10.25:1 compression, and dual four-barrel carbs. There is no consensus as to why Buick cancelled production of the nailhead, but it was replaced by the familiar 400/430/455 family of big-blocks in 1967.
While foreign elitists love ripping on our primitive, big-inch, pushrod engines, they often replace their high-tech, high-winding, turbocharged, weenie-displacement slugs with red-blooded American lumps.
Chevy W-series Big-Block
Anyone accustomed to conventional 90-degree V-8s will freak out upon tearing apart a W-series big-block Chevy for the first time. Introduced in 1958 as the precursor to the Mark IV big-block, it incorporated many unique design elements. Instead of machining traditional combustion chambers into the cylinder heads, Chevy cut the deck surface of the block at a 74-degree angle to the cylinder bore centerline. In other words, the engine-mount side of the block was taller than the lifter valley side of the block. This lopsided deck surface, in conjunction with piston crowns that sloped sharply downward toward the outside of the block, created a wedge-shaped combustion chamber at the top of the cylinder, in the block itself. This arrangement was said to improve quench, flame front travel, and cylinder pressure to maximize low-end torque.
Whether their unique combustion chamber design accomplished that mission is up for debate, but what's certain is that the W-series big-blocks ran hard. Launched in '58, the 348 featured a 4.125-inch bore, and a 3.250-inch stroke. With an optional mechanical lifter camshaft and three two-barrel carbs, it produced 350 hp. By '61, Chevy replaced it with the 409, which used a larger 4.312-inch bore and a 3.500-inch stroke. The most potent version of this engine was released in '63, which produced 425 hp, thanks to a solid-lifter cam, dual four-barrel carbs, and an 11.25:1 compression ratio. GM also built a 427ci W-series engine as a drag race package, which was essentially a 409 with a longer 3.650-inch stroke, 13.5:1 compression, and a high-rise intake manifold. The 427 was conservatively rated at 430 hp, and it's believed that only 50 of them were built.
Taking into account that it was designed in the '50s, the fact that the 348, 409, and 427 each had variants that made 1 hp per cubic inch is very impressive. As racers pushed these engines to the limits, however, the heavy pistons necessary to achieve their odd combustion chamber design often led to connecting rod failure and severe engine damage. Furthermore, the in-block chambers reportedly reduced power above 6,000 rpm, prompting GM to replace the W-series engines with the Mark IV big-block. That said, the legacy of the W-series platform is that it served as the foundation for what would eventually evolve into one of the most mystical and powerful race engine platforms of all time, the Mark IV big-block Chevy
"...the heavy pistons necessary to achieve their odd combustion chamber design often led to connecting rod failure..."
Pontiac Cammer Straight-Six
These days, 300-plus horsepower six-cylinder engines are becoming the norm, offered by both domestic and foreign manufacturers. In many respects, a little-known Pontiac motor came close to offering V-8 performance in a six-cylinder package long before the current engines were conceived. As the head of Pontiac's Advanced Engineering team in the '60s, John DeLorean spearheaded a high-tech straight-six prototype engine that was equipped with a beltdrive SOHC. The late '50s had seen a sharp recession, and Pontiac was rolling the dice on the resurgence of fuel-efficient six-cylinder engines. By '61, DeLorean was wrist-deep in the project, intrigued by the promise of OHC valve actuation. He was inspired by OHC straight-sixes of the day offered by Mercedes, Alfa Romeo, and Jaguar for their balance of power and fuel economy.
Based on the Chevy OHV straight-six, Pontiac's cammer used a 3.850-inch bore and a 3.250-inch stroke for a total of 230 ci. While it shared the crank and rods with the Chevy engine, Pontiac cast its own block that extended the skirt 2.4 inches for improved rigidity. On the top end, the Pontiac six used large 1.920-/1.600-inch valves, actuated by a cam mounted in the valve covers. To cut down on valvetrain noise that was common with OHC engines, the Pontiac cammer was equipped with hydraulic lifters and a rubber timing belt in lieu of a chain. Rated at 165 hp, the Pontiac straight-six went into production in the '66 Tempest. A hopped-up version-equipped with a bigger cam, 10.5:1 compression, and a four-barrel carb-was offered as well, rated at 215 hp and 240 lb-ft of torque. The cammer six was also available in the '67-69 Firebird.
Its promise and potential aside, due to the high production costs of the Pontiac OHC straight-six, most buyers opted for V-8s instead, and GM dropped it following the '69 model year. Nonetheless, it's not a stretch to surmise that it served as a precursor to the potent OHC six-cylinder engines that power the new Camaro and Trailblazer. Furthermore, Pontiac engineers incorporated many of the design elements of the cammer six into prototype DOHC 389 V-8s intended for use in NASCAR. GM's corporate ban on racing prevented this engine from ever seeing competition, but it's rumored to have produced more than 500 hp.
Salvaged from a '50s DeSoto, this early Chrysler Hemi was built by Gene Adams Performance,
Chrysler FirePower Hemi
The infamous Gen II Chrysler Hemi is an engine that needs no introduction. Whether it was in NASCAR, NHRA Top Fuel, or at the local dragstrip, everyone was trying to chase down the big, bad Hemi. Interestingly, Chrysler dabbled with hemispherical combustion chambers 13 years before the 426 Hemi debuted in '64. Launched in 1951, the Gen I Hemi produced 180 hp from its 331 ci of displacement. By 1951 standards, that was pretty darned stout. Consequently, the significance of this engine is rather obvious. Without a Gen I Hemi, there would be no Gen II Hemi.
Not only did Chrysler beat Ford and GM to the OHV punch by several years, Mopar's first OHV engine design boasted trick hemispherical cylinder heads. Building upon expertise it earned while developing aircraft engines during WWII, Chrysler achieved this unique cylinder head architecture by placing the intake and exhaust valves on opposing sides of the combustion chambers. The primary benefits of this setup was that it allowed for a straighter path from the back of the intake port to the manifold, and created extra space for larger valves. Actuating the valves in a Hemi chamber with an in-block camshaft required titling the pushrods at extreme angles, but Chrysler was able to make this arrangement run reliably. The 331 was bored and stroked to 354 ci in 1956, and produced an impressive 355 hp in its top trim level. Chrysler then upped the ante with a raised-deck block in '57, which allowed increasing the stroke even more for a total of 392 ci. The dimensions of this tall-deck block were quite imposing, with a 4.562-inch bore spacing, and a 10.870-inch deck height. The 10.0:1 version of the 392 was rated at 345 hp, and proved very popular with drag racers. A fuel-injected 392 was offered in the Chrysler 300, which churned out 390 hp.
The Gen I Hemi wasn't marketed as a Hemi, and Chrysler dubbed it the FirePower V-8. Chrysler abandoned the Hemi cylinder head architecture in 1958 when production of the Gen I Hemi ended. It was replaced by more traditional and cheaper-to-produce wedge cylinder heads that were introduced along with the new B-series big-block platform that same year. Perhaps recognizing the promise of these hemispherical heads many years later, Chrysler revived the design with the launch of the Gen II 426 Hemi.
That said, the Hemi story doesn't end there. Before the Gen I Hemi was dropped in favor of the B-series wedge motor, Chrysler manufactured a line of "semi-Hemi" V-8s from '55 to '58 called the Spitfire for consumers who didn't want to pony up for the FirePower engine. They used the same 331 and 354ci short-block assemblies as the Gen I Hemi, but were topped with polysphere cylinder heads and a conventional inline valvetrain. The polysphere heads got their name from combustion chambers that resembled two half spheres, and the most potent 354ci variant checked in at 310 hp. Chrysler also produced a 301ci small-bore version of this engine for entry-level vehicles.
"Not only did Chrysler beat Ford and GM to the OHV punch by several years, Mopar's first OHV engine design boasted trick hemispherical cylinder heads."
The few enthusiasts who know anything worthwhile about the AMC V-8 probably think of it more as a Jeep engine than a genuine hot rod powerplant. That's a reasonable assumption considering that the AMC V-8 was widely used in pre- and post-Chrysler-era Jeeps until the early '90s. Plus, the AMC V-8 is enormously popular amongst off-road Jeep enthusiasts. Nevertheless, AMC's flagship engine has a storied history in the annals of muscle cars, and recently released aftermarket blocks and cylinder heads make it possible to transform one into a seriously wicked hot rod engine.
The first-generation AMC V-8, more commonly known as the Rambler V-8, was built from '56 to '66 for use in Nash, Hudson, and Rambler vehicles. It performed well for its time, with the 327ci variant churning out 288 hp in 1957, however, the thin cylinder walls and limited displacement potential of these engines make them uncommon in both Jeep and hot rodding circles. AMC completely revamped its V-8 for the '66 model year, offering it in 290, 343, and 390ci trim levels. Sized somewhere between a big-block and a small-block, the new Gen II AMC featured a 4.750-inch bore spacing, and a forged crank and rods. Very few parts between the Gen I and II engines interchange. The 390 offered in the '69 AMX was the top dog, generating 340 hp and 430 lb-ft of torque, courtesy of a four-barrel carb and 12.2:1 compression.
For 1970, the AMC V-8 was revised again with the launch of the tall-deck Gen III platform. The basic architecture of the engine remained the same, and improvements included a 5/32-inch raised deck height and revised higher-flowing cylinder heads. Consequently, this allowed for an increase in stroke, and displacement grew to 304, 360, and 401 ci. Power ratings between Gen II and III engines are difficult to compare due to the differences in SAE gross and SAE net rating systems, but as with all engines of the day, horsepower steadily dropped as emission standards tightened up.
Most hopped-up AMC V-8s are based on the Gen III block for its generous displacement potential. With a maximum recommended bore diameter of 4.195 inches and a 9.218-inch deck height, building a 450-plus cubic-inch engine is no sweat. Indy Cylinder Head offers both an aftermarket tall-deck block and cylinder head castings, which pushes the AMC platform to big-block Chevy territory. In fact, Indy sells turnkey 512ci crate AMC V-8s that make 840 hp on motor. How's that for a Jeep engine?