2.1L I-4 Turbo DieselEdit
"The 2.4 entered production in December 1994 for minivans and cloud cars with the four speed automatic transmission. In 2002, it was titled "PowerTech" in the Jeep Cherokee. It is due to be slowly replaced by the 2.4 liter World Engine."
IN JEEP WRANGLERS: In its rear-wheel drive configuration, this engine was used only in "SE" Wranglers from 2003 through 2006. Intake manifold is plastic. Radiator is cooled by a thermostat controlled electric fan.
The AMC (American Motors Corporation) straight-4 engine is used by a number of AMC, Jeep and Dodge vehicles from 1984 through 2002.
2.5L Straight-4 Edit
The 2.5L inline-4 is a shortened version of the 4.2L 258 I-6 engine bored to 3.88 in (99 mm) and de-stroked to 3.19 in (81 mm). The block is basically the same as the 4.2L I-6 with a larger bore and the two center cylinders removed. The head featured a new combustion chamber and port design which was later used on the 4.0L I-6 -- the 2.5L I-4 head is stretched by two cylinders in the center.
Instead of the standard AMC bell housing bolt pattern, AMC/Jeep engineers adopted the General Motors small V6 and four cylinder bolt pattern (commonly used with GM's transverse-mounted powerplants) for their new engine, because the 2.5 replaced four-cylinder engines which had been purchased from GM; and because AMC continued to buy the 2.8L V6 from GM until the 4.0L I-6 was introduced in 1987. The four-cylinder and V6 shared the same drivetrain components, whereas stronger transmissions were needed for the 4.0L I-6.
The AMC I-4 appeared in 1984 with the new XJ Cherokee and was produced through 2002 for the Jeep Wrangler and Dodge Dakota pickup, which used the AMC/Jeep designed four since 1996.
|Bore x Stroke||3.88" x 3.19"|
|Horsepower Output (final year)||123 HP SAE (89 kW) @ 5,400 rpm|
|Torque Output (final year)||145 ft lbs (197 N·m) @ 3,250 rpm|
|Valvetrain||Eight overhead valves|
|Compression ratio||9.1:1 to 9.2:1 depending on year|
|Firing Order||1-3-4-2 Clockwise (see image)|
The final production year used sequential mulitple-port fuel injection. For comparison, the 4.2L I-6 produced 112 HP @ 3,200 rpm and 210 ft lbs of torque @ 2,000 rpm in its final year with the computer controlled carburetor.
For several years, the engine was detuned for the Wrangler; from at least 1992 to 1995, it produced 130 horsepower and 149 ft lbs of torque with 9.2:1 compression in the Cherokee and Comanche.
2.5L Turbo DieselEdit
R428 2.8L/RA428 2.8L Turbo DieselEdit
This in-line 4 cylinder diesel motor is produced in Italy by VM Motori. The engine features:
- 2776 cc of displacement
- 4 valve/per cylinder
- belt-driven DOHC
- finger followers on the camshaft
- BOSCH common rail direct injection at 24,000 psi
- wet liners
- rotary vane oil pump
- two gear-driven balance shafts
- cooled EGR
- viscous water heater unit
- optional VGT turbocharger (Garrett in Jeep applications)
- weighs 485 pounds/ 220 kilograms
- Stock power rating of 160HP/295 foot pounds in the 04-07(05-06 in NAFTA market) KJ Liberty application.
RA428 2.8L Turbo DieselEdit
This in-line 4 cylinder diesel motor is produced in Italy by VM Motori. This engine is a newer version of the R428. While having the same displacement and bore and stroke, this engine is a different block than the R428. This engine is used in the JK Wrangler outside of the U.S. market. This engine is often reffered to by its development codename: Panther. This engine features:
- 2776 cc of displacement
- 4 valve/per cylinder
- BOSCH common rail direct injection with electric piezo injectors operating at 30,000psi
- electronically controlled VGT turbocharger
- weighs 451 pounds/ 205 kilograms
- power rating of 174 horsepower, 340 foot pounds
Under powered for the duty
Indeed, if you're looking for power under the hood of a Jeep, look elsewhere. However, with proper tuning and maintenance, the 2.8L V6 can be a servicable powerplant.
The 2.8L is a sixty degree V6 manufactured for Chevrolet as an economy motor. It was installed in Jeep vehicles with a two-barrel Rochester carburetor. (One barrel is a primary while other is a vacuum-actuated secondary.)
Many 2.8L owners have reported improved performance after installing a high-performance air filter, such as those made by K&N. High performance parts, such as camshafts and aluminum, four-barrel intakes are also available. However, owners shouldn't expect significant power gains from such hardware.
The 2.8L V6 can often have trouble passing emissions tests, especially at high altitudes. The state of Colorado emissions control web site recommended installing a PCV valve for the Chevrolet 305 V8 and adjusting the metering rod in the carburetor primary to keep it from lifting prematurely.
2.7L 5 cyl Turbo DieselEdit
The 4.0 L (242 in³; 3956 cc) straight-6 was an evolution of the 4.2L 258 I-6 and 2.5L I-4 and appeared in 1987. It had the same 3.88 in (98.4 mm) bore as the 2.5 with a longer 3.41 in (86.7 mm) stroke. The 4.0 was discontinued at the end of the 2006 model year as the redesigned Jeep JK Wrangler uses Chrysler's 3.8L V-6 OHV V6.
The first 4.0 engines in 1987 had RENIX (Renault/Bendix) engine control systems, which were quite advanced for their time, but are now handicapped because there are very few scan tools which can be "plugged in" to a RENIX system for diagnosis. The Renix also used a very advanced engine knocking sensor, which allowed the computer to know if detonation was occurring, thus allowing the computer to make the appropriate changes to prevent this.
The 1987 RENIX 4.0 made 173 hp (129 kW) and 220 lb-ft (298 N·m) of torque. In 1988 the 4.0 received higher flowing fuel injectors, taking output to 177 hp (132 kW) and 224 lb-ft (304 N·m) respectively.
In 1991 Chrysler Corporation, then the owners of the Jeep brand, redesigned the RENIX engine control computer and raised the intake ports approximately 1/8″ for a better entry radius. Chrysler also enlarged the throttle body and redesigned the intake and exhaust manifolds for more efficiency, and the fuel injectors were once again replaced with higher flowing units. The camshaft profile was also changed. The net result of all these changes was an engine that made 190 hp (142 kW) and 235 lb-ft (312 N·m) of torque. Badging on Jeeps equipped with this engine read "4.0 Litre HIGH OUTPUT". The new cam profile combined with altered computer programming eliminated the need for an EGR valve and knock sensor, but make the engine more sensitive to alterations, especially where emissions are concerned.
Small changes were made to the cylinder head for the 1995 model year. In 1996, the engine block was redesigned, and a new strengthened unit was then used. The new block made use of more webbing cast into the block, and a stud girdle for added rigidity of the crankshaft main bearings. The cylinder head was also again changed around 1998 to a lower flowing, but more emissions friendly, design. Engines installed in 1999 Grand Cherokees carried the Power Tech name, which was subsequently passed on to 4.0s in all Jeep models.
The 4.0 engine was in production in North America until 2006, when the Jeep Wrangler TJ was replaced by the new JK design that uses Chrysler's OHV 3.8L V-6. It is foreseeable that this engine may be made for many more years in the People's Republic of China, where a slightly modified version of the XJ Jeep Cherokee with 2.5L I-4 and 4.0 engines are still being produced.
Output as of 2004 was 190 hp (142 kW) at 4600 rpm with 235 lb-ft (312 N·m) of torque at 3200 rpm.
This engine is considered one of the best offroad engines ever made. The extreme low end torque is ideal for trailing and rock crawling. The only downfall to the engine is the low power output for mudding applications but this can be fixed with various aftermarket options including a supercharger for the engine. Interchangeability within the late AMC/Jeep engine family is superb. The better flowing 4.0 L heads can easily be modified to fit earlier engines right along with the fuel injection system. The longer stroke 258 crankshaft and rods will drop right in the slightly larger bore 4.0 L block, easily creating an even higher torque 4.5 L engine with the stock bore (4.6 L bored 0.030″ over, and 4.7 L with a 0.060″ overbore). Blocks should be sonic checked for adequate cylinder wall thickness before boring 0.060″ over.
4.2L 258 I-6Edit
This iron block 258 cubic inch I-6 cyl was introduced in 1971 and stayed in the jeep family until 1990.
Gladiator/J-Series Trucks pickups and the Wagoneer were the first to use this engine. In 1972 the CJ's (including the CJ-5) were powered with this reliable mill. And finally, In 1987 the YJ Wrangler used the low end tourque and HP from the venerable '6' until the end of 1990 when the 4.0L I-6 took over. When comparing the later 4.0L and the 258 the main difference is the stroke of the pistons (3.41" and 3.90" respectively). The 258 has a cast iron block and cylinder head, hydraulic lifters (non-adjustable rockers), and 7 main bearings. The main strengths of the 258 are it's reliablity, low cost, low RPM horsepower and torque peaks, and serviceability. It's biggest weakness is the Carter Carb.
This engine came carbureted from the factory, and used either the Carter BBD (double barrel) or Carter YF (single barrel) carburettor.
|Bore x Stroke||3.75" x 3.90"|
|Firing Order||1-5-3-6-2-4 Clockwise(see image)|
|Carburettor options||2 Barrel Carter BBD|
|1 Barrel Carter YF|
American Motors Corporation (AMC) produced a series of widely-used V8 engines from the mid-1950s before being absorbed into Chrysler. Some continued well after the merger in Jeep vehicles until 1991. Formerly known as the "Rambler V8", many new AMC enthusiasts refer to this engine family as the "GEN-1" AMC V8. Prior to the formation of AMC, Nash Kelvinator President George W. Mason desired to negotiate a merger between Nash, Hudson, Studebaker and Packard. Initially he had a verbal agreement with Packard that the two companies would supply parts for each other when practical. AMC started buying Packard V8s in 1954 for the big 1955 Nash Ambassador and Hudson Hornet. These were supplied with Packard "Ultramatic" automatic transmissions - exclusively. AMC sent Packard some parts bids, but were rejected as too expensive. An incensed George Mason ordered his engineering department to develop an in-house V8 as soon as possible. The engineering department hired David Potter, a former Kaiser Continental engineer, to come in and help develop AMC's first non-inline engine. Potter had previously been involved with a V8 plan for Kaiser, but both Nash and Hudson design elements can be seen in the design. From drawing board to full production in just under 18 months was an engineering feat in itself.
All these engines are externally identical, weigh in at 601 lbs (only 26 lbs more that the famed '55 small block Chevy), and feature a high quality forged steel crankshaft, connecting rods in a very rigid "Hudson X" style crank gallery, a Nash style shaft mounted rocker arm system and an excellent lubrication system that serves as a model of oiling system design theory. Engine displacement was varied by bore dimension to reduce tooling costs and streamline the manufacturing process. The 250 has a 3.50" bore, 287 3.75", and the 327 a 4.0" bore. Bore size is cast on the top of the block near the back of the right bank cylinder head.
AMC's first V-8, the 250, was used in American Motors Corporation automobiles from 1956 through 1961. As the name implies, it had 250 in³ (4.1 L) of displacement and was a modern (for the time) OHV/pushrod engine design and made its debut in the Nash Ambassador and Hudson Hornet "Specials" of 1956. These cars had the top of the line model trim, but were built on the shorter wheelbase (Statesman and Wasp) models (hence the "Special" name). The 250 used solid lifters and came in two and four barrel carburetor varieties (4V only in Nash/Hudson "Specials").
All 1958-60 V-8 Ramblers were called "Rebel" (not to be confused with the 1957 Special Edition Rebel). In 1961 The Rambler Six was renamed the Rambler Classic to avoid model confusion in the Rambler line-up. A V-8 then became an option in the Classic instead of a separate model.
By US auto industry convention, the V8 engine was a controversial design for manufacturers who held to the merits of inline 8 engine construction, such as Nash, Hudson and Chevrolet. But for consumer percieved charisma, potential benefits of increased power to weight ratio and reduced overall height for future body shell designs among other issues, the V8 engine became all the rage in the early fifties. The AMC Rambler V8's displacements reflect the similar displacements of the previously popular inline 8s as well as the quite similar displacements offered by the competition.
In mid model year 1963, AMC introduced a 287 in³ (4.7 L) V8. When the 250 was dropped in 1961, there was no V-8 option for Rambler models other than the top of the line Ambassador. Dealers complained, so the 287 was introduced as an option for the "mid size" Rambler. Like the 327, it used hydraulic valve lifters. Only 2V models were produced, there were no 4V options from the factory as this was the economy model V-8. The 287 was produced through 1966.
Engine bay of a 1963 AMC Ambassador with a 327 V8 4-barrelThe AMC 327 was similar to the 287, but displaced 327 in³ (5.4 L) due to the bore increase to 4.0". Unlike the 250, the 327 came with hydraulic valve lifters.
This engine debuted in a special edition Rambler Rebel of which only 1500 were made. All had silver paint with a gold-anodized "spear" on each side. This was to be the first electronic fuel injected (EFI) production engine, but teething problems with the Bendix "Electrojector" unit meant that only a few engineering and press cars were built, estimated to be no more than six units. However, at least two regular production Rebels with EFI were known to have been built. One was sent to Daytona Beach, Florida for "Speed Week" (the forerunner of today's Daytona 500). It was the second fastest car on the beach, bested only by a 1957 Chevrolet Corvette with mechanical fuel injection, and only by a couple tenths of a second. The EFI 327 was rated at 288 hp, and the production 4V carbureted model at 255 hp. All the EFI cars were reportedly converted to 4V carb before being sold; none are known to have existed outside the engineering department at AMC. The main problem was that vacuum tube and early transistor electronics just could not keep up with the demands of "on the fly" engine controls.
The 327 was not available in any other Rambler models in 1957 beside the Special Edition Rebel. The Nash Ambassador and Hudson Hornet "Special" models were dropped after 1956, replaced by standard wheelbase models with the 327 V-8 instead of the 250 V-8. When the big Nash and Hudson cars were dropped after 1957, they were replaced by the 1958 "Ambassador by Rambler" — a stretched Rebel (Rambler V-8) with the 327 V-8 instead of the 250. The 327 was exclusive to the Ambassador line, and could not be ordered in a Rebel or Classic. The 327 was also sold to Kaiser Motors from 1965 to 1967 for use in the early Wagoneers and the Gladiator pick-ups. Kaiser switched to Buick 350s in 1967 to power these vehicles. The GM engine was used up to 1970 when Jeeps once again were powered by AMC. That was the year American Motors acquired the Jeep Division of Kaiser.
GEN-2 AMC Short-Deck V-8 (1966–1970) Edit
Engine bay of a 1967 AMC Marlin with a "Typhoon" 343 V8 4-barrelThe new-generation AMC V8 was first introduced in 1966. It is sometimes referred to as the "GEN-2" AMC V-8. A curious linkage exists between the '62 Buick V6 and this second AMC V8 design wheras Buick had sold their V6 factory to Kaiser, Kaiser then dubbing it the "Dauntless V6". It was during this time that AMC released their newer V8 engine which appears to be a near copy of Buick's original V6 design, but with two more cylinders added on to the rear of the engine. AMC went on to purchase Kaiser's automotive operations and about that time the V6 factory was sold back again to Buick. The 290cid AMC V8 debuted in '66. A 343 version debuted in '67, having a larger bore with the same crank and rods. Four barrel versions of the 290 and 343 were named "Typhoon 290" and "Typhoon 343". The typhoon name alludes to AMC's nearest competitor Chrysler who was threatening the entire US auto industry with the release of a full production turbine engine, whereas the names "Typhoon" and "Turbine" are similar subliminal word pictures which suggest a similar turning motion. The famous "AMX 390" debuted in '68, in AMC's new AMX two seater model automobile. All three engine sizes (290, 343, and 390) share the same basic block design — the different displacements are achieved through various bore and stroke combinations. All blocks share the same external measurements and thus can be swapped easily. Contrary to a popular myth, the AMC V8 was not built by Ford or anyone else. They did share some electrical parts (starter and distributor) with Fords, and some models used Motorcraft (Ford) carburetors, but the engine design is totally different. Bore center measurement was kept the same as the GEN-1 AMC V-8 so that boring equipment could be reused. Other than that, this engine is vastly different from the GEN-1 model. The GEN-1 engine is physically the size of a big-block Ford or GM engine, and is sometimes called a "big-block". The GEN-2 is closer to the physical size of US made small-block V-8s except for the bore centers, which are the same as some big-block engines. There are no shared parts between the AMC GEN-1 and GEN-2/3 engines.
The GEN-2 AMC V-8 was first introduced at 290 in³ (4.8 L) in 1966. It was used exclusively in the American model the first year (some reports indicate a few late production Classics had 290s substituted for 287s, but that hasn't been substantiated). The 343 in³ (5.6 L) came out in 1967 and the AMX 390 in³ (6.4 L) arrived in 1968. These engine blocks were unchanged through 1969.
The head used during this time are the so-called rectangle port, named after their exhaust port shape. The 290 heads use smaller valves, 1.787 in (45.4 mm) intake and 1.406 in (35.7 mm) exhaust, in order to prevent problems with the small bore. The 343 and AMX 390 used the same larger valve heads, 2.025 in (51.4 mm) intake and 1.625 in (41.3 mm) exhaust.
The base 290 in³ (4.8 L) 290 produced 200 to 225 hp (149 to 168 kW) with a 2V and 4V carburetor, respectively. It was built from 1966 through 1969. It has a 3.75 in. bore (95.25 mm) and 3.28 in. (83.31 mm) stroke.
The 343 in³ (5.6 L/5622 cc) 343 has a 4.08 in. (103.6 mm) bore and 3.28 in. (83.31 mm) stroke. The basic 343/2V produced 235 hp (175 kW) and was built from 1967 through 1969. Output for the optional 4V carburetor version was 280 hp (209 kW) and 365 ft·lbff (495 N·m) gross. This version had a 10.2:1 compression ratio.
AMX 390 Edit
In addition to the largest bore and stroke, the 390 in³ (6.4 L) AMX 390 motor also got heavier main bearing support webbing and a forged steel crankshaft and connecting rods. AMC engineers tested the AMX 390 crankshaft and rods for 8000 rpm potential. The 390 engine became so popular that the option was cancelled for the '69 AMC Rebel for production capacities. The AMX 390 was conservatively rated at 315 hp (235 kW) and served as AMC's top engine from '68 to '70. Bore is 4.165 in. (105.791 mm) and stroke is 3.68 in. (93.47 mm). Maximum factory recommended overbore is only 0.020", though they are commonly bored 0.030".
GEN-3 AMC Tall-deck (1970-1991) Edit
Engine bay of a 1970 Javelin with a Ram Air 390 V8In 1970, all three blocks grew in deck height and gained a new head design. These changes made this the third generation of AMC V-8, hence it is sometimes referred to as the GEN-3 AMC V-8. The stroke and deck height on the 290 and 343 was increased by 0.16" (~5/32"), becoming the 304 and 360, respectively. The AMX 390 remained at the same displacement by using a special rod and piston for this year only. It is believed that AMC kept the 390 this last year due to the reputation it had garnered in the two seater AMX, which was discontinued after 1970. In 1971 the 390 was stroked by 0.16" to become the 401.
The other change in 1970 was the switch to the dog-leg heads. These heads flow ~20% better on the exhaust side than the 66-69 rectangle port heads and are thus the best for performance. There are two reasons for the flow increase: First, the area of the port is larger, due to the dog leg. Second, the shape of the port floor was changed from a concave to a convex curve. The concave floor tended to bend the exhaust flow upwards which caused turbulence when the flow was forced to go down into the exhaust manifolds. By switching to a convex floor the curvature of the flow starts in the head and proceeds much more smoothly into the exhaust manifold resulting in less turbulence and better flow.
The center two intake bolts on each head were relocated to prevent accidental mix-ups of GEN-2 and GEN-3 intakes. The intakes can be interchanged by slotting the bolt holes, but the added deck height of the GEN-3 engine means that sealing and port match will be compromised. GEN-3 intakes can be machined to fit GEN-2 engines by surface grinding the intake flanges (by a machine shop) and slotting the center holes.
There is a persistent myth about 1970-mid 1971 "319" or "291" AMC heads. These heads have the dog-leg exhaust ports and 50-52 cc combustion chambers. They are commonly identified by the first three (319) or last three (291 for the 360-401 heads; 304 used a different casting) digits of the casting number. There was a US auto industry wide shift to lower compression ratios in mid 1971, so AMC increased combustion chamber size to 58-59 cc. The first three digits of the casting number on the large chamber heads are 321, 322, or 323 depending on year. The ONLY difference between small and large chamber GEN-3 heads is the combustion chamber size. The early heads are not "the best" AMC heads as many have come to believe. They will raise compression on a later engine with no other changes, but if building an engine get the proper pistons for the desired ratio. There is no reason to search out these relatively hard to find, and more expensive when found, heads for performance.
The AMC 304 was used in J-series pickups and Wagoneers in 1971-1972, and in the CJ's in 1972-1981.
Horsepower and Torque by year:
1971 Horsepower (gross) 210 at 4400rpm Torque (gross) 310 at 2600rpm
1972 - 1978 Horsepower 150 at 4200rpm Torque 245 at 2500rpm
1979 Horsepower 130 at 4200rpm Torque 245 at 2500rpm
1980 - 1981 Horsepower 125 at 3200rpm Torque 220 at 2400rpm
The AMC 304 uses a cast iron block and heads with over head valves and hydraulic lifters.
The AMC 360 in³ (5.9 L) 360 2-barrel produced 235 to 245 hp (175 to 183 kW) in 1970 to early 71 while the 4-barrel produced 285 to 295 hp, 175 to 220 hp from mid 71-75, 140-180 hp in 1976, 129 hp in 1977, and 140 hp from 1978-91. It was the last AMC V-8 to be manufactured. It was used exclusively in Jeep J-series Trucks 1970-1987, Jeep Wagoneer models from 1972-84, Cherokee from 1974 to 1983, and Grand Wagoneer from 84 to 91.
The AMC 390 in³ (6.4 L) 390 produced 325 hp (245 kW) in all except the Rebel Machine. This muscle car engine was rated at 340 hp (254 kW) due to a different intake. Production only lasted one year (1970) before it was stroked to become the 401. Like its GEN-2 cousin, the maximum factory recommended overbore is only 0.020", though they are commonly bored 0.030".
The 401 in³ (6.6 L) 401 produced 330 hp (246 kW) gross in 1971 and 255 hp (190 kW) net 1972-75. In 1976 it was rated at 215 hp. It was last produced in 1979. It was used exclusively in full size Jeeps 1974-79. Like the 390, the 401's crankshaft and connecting rods are forged steel. Like the 390, factory recommended overbore is only 0.020", commonly bored to 0.030".
"Service Replacement" Multi-Displacement Block Edit
There was also a "Service Replacement" block made as a modified GEN-3 design. This is a 401 casting (same casting number) without the displacement cast into the side and with a 360 bore and thicker deck. In theory this single block could be built as any 343-401 GEN-2 or GEN-3 engine. A dealer could stock one or two blocks to use for warranty replacement. It was also sold as a heavy duty racing block, which is speculated to be the real reason it was produced in the first place. It appeared in 1970 in time for the 1971 Trans-Am racing season. Since it was a standard factory part it did not have to be homologated under T/A rules, and was not used in the 2501 "Mark Donohue" Javelins built to homolgate the "duck tail" spoiler. Those received standard 360 or 401 engines.
This article relates to the Magnum series Chrysler engine, not the older LA series 318 CID used in Mopar cars.
The 5.2L (318 cid) engine used in the Jeep vehicles is known as a Magnum series engine. It has a cast-iron engine block and cylinder heads, with a overhead valve configuration consisting of 16 valves controlled by hydraulic lifters and aluminum pushrods. The intake manifold is known as a beer-barrel design due to it's high rise. The fuel delivery system is a tuned-port design utilizing a common fuel rail.
It was offered in 1993 to 1998 Jeep Grand Cherokees.
5.2L V8 318 ci engine. it is one of the largest engines that came in the ZJ series of jeeps, actually the largest except for the optional 5.9 in the 98 Grand Cherokee. It holds 6 quarts of oil and aproximately 3.5 gallons of coolant. The engine is rated at 220 horses and 285-300 ft-lbs of torque. However this can easily be improved upon with the introduction of a cold air system which K&N rates at 25 added hp and approximately 40 added ft-lbs of torque.
The 5.7L HEMI V-8 is offered in the WK Grand Cherokee. It is a modern powerplant that produces an impressive 325 horsepower and 375 lb-ft of torque.
In order to boost fuel economy, the engine utilizes Multiple-Displacement-System (MDS) which deactivates four of the eight cylinders when they are not needed.
Chrysler has developed another modern Hemi, this time at 6.1 L. The displacement is 370 cubic inches (6,059 cc). The engine is bored-out to 4.1 inches (103 mm), but many other changes were made to allow it to produce 425 hp (317 kW) at 6,200 rpm and 420 ft·lb (569 Nm) at 4,800 rpm. The engine block is different, with revised coolant channels and oil jets to cool the pistons. A forged crankshaft, lighter pistons, and strengthened connecting rods add durability. A new cast aluminum intake manifold is tuned for high-RPM power and does not include variable-length technology. Chrysler's Multi-Displacement System is not used.