Modifying a late-model Hemi engine
Livernois Motorsports’ range of late-model performance parts gives enthusiasts a leg up on the General’s troops and the Blue Oval boys
Story Barry Kluczyk - May 01, 2011 09:00 AM
The third-generation Hemi has been held back in the power-upgrade department by the lack of reliable tuning that enables strong drivability attributes, but that is changing as enterprising tuners are finally making headway in that important department.
Livernois Motorsports’ stroker rotating assemblies use new, 4340-forged steel crankshafts to add 25 cubic inches to the 5.7 liter engine and 56 cubes to the 6.1 liter engine, for a total of 392 and 426 cubic inches, respectively. Matching the longer-reach crankshafts are forged rods, which replace the cast factory parts. Livernois uses super-stiff Manley H-beam rods and ARP 2000 fasteners. The Diamond forged pistons are stronger than the factory cast pistons and support higher horsepower and a greater rpm range. They can also be specified for lower compression to suit supercharged applications. The gold coating is a ceramic-based thermal barrier.
Livernois Motorsports also offers CNC-ported heads for the 5.7 liter and 6.1 liter engines to match the greater airflow needs created when the stroker kits add significantly to the engines’ displacement. The heads are delivered completely assembled, including the springs, retainers, etc.
The heads are machined on a five-axis CNC machine, ensuring precise and identical changes to every port. The process enhances the intake and exhaust ports, but leaves the combustion chambers alone. The decks are left essentially unchanged, too, to preserve the compression ratio and ensure pump-gas compatibility. After the ports are machined, each head – depending on whether it’s a Stage 1, 2 or 3 – receives a multi-angle valve job to smooth and enhance airflow. It’s a time-honored power-building technique that still works very well.
The CNC-machined heads’ effectiveness was corroborated on the flow bench, where the 5.7L heads added more than 40 cfm at 0.500-inch lift and more than 60 cfm at 0.600-inch. On the 6.1L heads, the port work increases airflow to 350 cfm at 0.500-inch and 365 cfm at 0.600-inch lift – an increase of about 25 percent over the stock heads’ airflow ratings.
Here, the machined intake and exhaust ports are visible, as well as the valve seats, but the combustion chamber is left as-cast. The two holes at the center of the chamber are for the cylinder’s twin spark plugs. Depending on the performance stage, Livernois’ heads come with either stock valves or a set of stainless Manley valves.
Livernois Motorsports recommends rounding out the heads and stroker kit with a higher-lift camshaft. And like the stage kits for the heads, they offer three versions to complement the airflow of the heads. Although relatively aggressive, the cams deliver good idle quality and excellent drivability across the rpm band.
None of the power enhancements offered by the stroker kit, heads and cam could be realized without proper tuning, which has only recently become available. Here, Livernois Motorsports’ Dan Millen configures downloads a power package’s parameters to a DiabloSport handheld tuner. The Predator holds the revised tuning and uploads it to the vehicle’s engine controller. It’s a relatively simple “plug and play” operation that takes only a few minutes to give the controller new directions about the engine’s displacement and other upgrades.
For die-hard Mopar enthusiasts, the advent of the third-generation Hemi has been a source of joy and frustration.
The joy comes from the undeniable performance the engines offer, whether in 5.7-liter or SRT8-exclusive 6.1-liter forms. The frustration has been a relative lack of high-performance options that are readily enjoyed by GM jockeys driving LS-powered vehicles and the Ford guys with their modular V-8s.
Indeed, a lack of viable, consistent and, frankly, reliable Hemi tuning has been a problem for years and that has stymied the development of additional performance upgrades. After all, what good is a hotter camshaft if there’s no tuning to work with it?
Fortunately, the tide is turning, as more and more computer-savvy enthusiasts and aftermarket companies chip away at the Hemi’s electronically-controlled brain. At the forefront of this new Hemi revolution is Detroit-area tuning house Livernois Motorsports. Directed by drag racing champ Dan Millen, the shop is aggressively courting modern Hemi enthusiasts with a variety of head, camshaft and rotating assembly upgrades. He pretty much had no choice, as customers were dropping off their Mopars and telling him, “Make it faster. Now!”
With the assistance of DiabloSport, which has helped Livernois Motorsports match engine changes with strong tuning, a variety of packages have been brought to the table. According to Millen, however, those packages work best on vehicles made after about the mid-point of 2005. The controllers in those vehicles are much more agreeable to accepting the necessary changes to their air/fuel tables.
“They make really good power if you can get the computer to cooperate,” he says. “Vehicles with computers from roughly the last half of the 2005 model year and later respond the best. There were significant changes to the production controller and we find they’re the easiest to work worth.”
In fact, Millen adds, he suggests investing in power equipment for a car equipped with the earlier computer may not bring a good return on investment.
“If you’ve got an early ’05 car or something older, you’re better off buying a new controller from the dealer and starting with it,” he says. “It’s better in the long run, because it’s easier to tune and you’ll ultimately get more power and better drivability.”
Drawing in More Cubes
Anchoring Livernois’ Hemi performance portfolio is a line of stroker kits for both 5.7-liter and 6.1-liter engines. The all-forged kits take the 345ci 5.7 liter Hemi to 392 inches, while the 370ci 6.1 liter engine is stretched 56 cubes to displace a classic 426 cubic inches.
“The engines really respond to the stroker kits, because we’re able maintain not only the optimal air/fuel ratio, but the details of the controller that are driven by manifold pressure,” says Millen. “Drivability is great.”
Forged crankshafts, connecting rods and pistons are essential for ensuring durability under the higher loads that high-performance engines typically experience. The factory 5.7 liter and 6.1 liter engines use powder-metal rods and hypereutectic (cast) pistons that are admirably strong for the engines’ respective stock operating ranges, but they’re simply not designed for the demands of larger-displacement combinations that could add 25 percent or more horsepower and torque.
On demand, Livernois Motorsports can also assemble a rotating assembly with blower-friendly, lower-compression pistons that help stave off detonation. That’s a serious concern in stock engines, as the 5.7 liter and 6.1 liter engines have 10.5:1 and 10.3:1 compression ratios, respectively.
Complementing the stroker kits for maximum effectiveness is Livernois’ ported heads, again for both 5.7-liter and 6.1-liter engines. The heads are cut on a five-axis CNC machine, then treated to a precision valve job. The porting work opens up the passages and improves airflow significantly. With the 5.7 liter heads, intake flow increases by about 43 cfm at 0.500-inch lift and a whopping 62.5 cfm at 0.600-inch lift, for a rating of 342.5 cfm – that’s better than a 22 percent improvement at 0.600. It’s a similar story with the enlarged 6.1 liter heads, which flow 350 cfm at 0.500-inch and 365 cfm at 0.600-inch lift.
Livernois offers three stages of modified cylinder heads, defined by these attributes:
• Stage 1: Uses stock valves and guides, with Livernois-supplied beehive springs rated to 0.600-inch lift (5.7-liter) or 0.625-inch lift (6.1-liter).
• Stage 2: Uses Manley stainless valves and new bronze guides, a CNC valve job and includes Livernois-supplied beehive springs rated to 0.600-inch lift (5.7-liter) or 0.625-inch lift (6.1-liter).
• Stage 3: Uses Manley stainless valves and new bronze guides, a CNC valve job and includes Livernois-supplied beehive springs rated to 0.650-inch lift (5.7-liter and 6.1-liter); also includes titanium retainers.
Prices on the head packages (no core exchanges required) range from about $1,900 for the Stage 1 5.7L heads to about $3,300 for the Stage 3 6.1L heads.
When the stroker kits are slipped inside a production engine and the new heads installed, they work surprisingly well together, delivering nearly the equivalent power increase of a low-boost blower. Millen says the 5.7 liter kit typically increases output by about 100 to 125 horsepower at the wheels – or taking rear-wheel power from about 275 to more than 375. For the 6.1 liter engine, the payoff is similar: about 100 horses at the wheels. That takes rear-wheel power from roughly the stock 350 mark to about 450.
The power numbers cited above include not only the heads and stroker assemblies, but a camshaft swap, too. Livernois Motorsports recommends a higher-lift camshaft to round out the enhanced airflow capability of the engines. At the very least, the engine won’t breathe as well or rev as high without a new cam. Although there are several off-the-shelf camshafts in the aftermarket to pick from, Livernois offers a trio to match the three stages of cylinder head packages.
The specifications for them include:
• Stage 1: 0.522/0.525-inch lift, 208/212-degrees duration and a 113-degree lobe separation angle.
• Stage 2: 0.528/0.531-inch lift, 216/220-degrees duration and a 113-degree lobe separation angle.
• Stage 3: 0.547/0.555-inch lift, 224/228-degrees duration and a 114-degree lobe separation angle.
Millen says custom grinds are offered, too, including those intended for use with forced induction. Regardless of the application, adding a camshaft to the equation reinforces the need for careful tuning. And because Livernois’ tuning is done individually – there’s no “standard” tune that is packaged for remote installation – the company typically installs the engine upgrades and final tuning at its Dearborn, Michigan, facility.
“It’s the best option for our customers, even if they have to travel a longer distance to drop off their car,” says Millen. “That way, each vehicle receives a custom, optimized tune that backs up the engine work that we performed.”
But the fact that tuning is no longer an obstacle is huge. There may not be as many options yet as there are for the other Detroit-based competitors, but you can expect the offerings to start multiplying exponentially – with frontline tuners like Livernois Motorsports leading the way.
Bigger is Better – Inside the 6.1L Hemi
The larger-displacement, more powerful 6.1 liter Hemi engine was introduced on a variety of Chrysler’s SRT high-performance models starting in 2005. It is rated at 425 horsepower and 420 lb-ft of torque.
More than merely larger and more powerful than its 5.7 liter cousin, the 6.1 liter Hemi boasts a unique block casting, higher-flow cylinder heads and numerous other changes. Here’s a rundown of how the 6.1 liter differs from the 5.7 liter engine:
• The cylinder block has reinforced bulkheads to handle higher engine loads
• Increased bore diameter to 4.05 inches vs. the 5.7 liter’s 3.95-inch bores
• Cylinder bores honed with torque plate for more precise bore and reduced piston friction
• Forged micro-alloy steel crankshaft with tri-metal main bearings vs. nodular iron crank of the 5.7 liter engine
• Specific, high-strength powder-metal connecting rods
• Higher-load flat-top pistons designed to support the 6.1 liter engine’s higher compression ratio
• Piston-cooling oil jets that squirt oil on the underside of the pistons; a unique oil pump pressure relief valve accommodates the jets’ oil flow
• Revised oil pan and windage tray designs, which manage oil return to the pan sump at higher engine speed
• Billet-steel, high-strength camshaft with higher lift (.571/.551-inch), longer duration (283/286 degrees) and increased overlap (50 degrees)
• Cylinder heads with increased port size, for 11 percent increased intake flow and 13 percent higher exhaust port flow compared with 5.7 liter engine
• Lightweight intake valves with hollow stems and 2.07-inch head diameters – 0.07-inch larger than the 5.7-liter engine
• Larger, 1.59-inch exhaust valves with sodium-filled stems
• Specific valve springs with external dampers
• Unique, cast aluminum intake manifold with shorter, larger-diameter and tapered runners designed for high-rpm performance; the internal runners are core-dipped to smooth the surface finish for improved airflow
• Exhaust manifolds have a true, tubular “header” design and are wrapped in a stainless steel shell; the manifolds offer increased gas flow for the equivalent of 12 additional horsepower compared to the 5.7 liter engine’s manifolds.
• Fuel injector flow capacity increased by 14 percent, compared with the 5.7 liter engine
• The 6.1 liter Hemi is instantly recognizable, thanks to its specific aluminum intake manifold and black “wrinkle finish” valve covers. MDS cylinder deactivation is not enabled on the 6.1 liter engine.
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