Livernois’ 401-Cube Gen-III HEMI Gets A Stout Top End

In our last article, we brought you the bruiser of a bottom-end Livernois Motorsports built to showcase its new foray into Mopar performance. Now, it’s time to top off the combination with more of the decades of experience Livernois brings to the table.

6.2-Liter Hellcat Cylinder Heads

The core of the top end is a pair of OEM 6.2-liter Hellcat cylinder head castings. Bringing their expertise in porting factory castings over from the Ford side of the business, Livernois offers several different options for cylinder head porting for factory Gen-III HEMI cylinder heads.

For this engine, Livernois opted to go all-in with their Stage 3 Race Series package. The Stage 3 package starts off with CNC intake and exhaust ports, designed and refined in-house at Livernois using computational fluid dynamics and finite element analysis modeling, combined with SuperFlow SF600 flow bench testing and real-world dyno testing. The ports are cut on Livernois’ 5-axis CNC mill for precision to the design and repeatability between ports. Peak flow of the ports is 386 cfm at .600 inch of lift on the intake and 242 cfm out of the exhaust.

Livernois Motorsports HELLCAT 6.2L HEMI Race Series Cylinder Head Flow Chart

Next, custom Livernois-Spec Manley intake and exhaust valves are fitted with a CNC valve job to match the seat angles of the new custom valves. The valves are fitted with new valve seals before all of the other valvetrain components are installed. The heads are secured to the block with a set of ARP head studs and sealed with a set of MLS head gaskets.

A Performance HEMI Valvetrain

A Livernois Hellcat Stage 2 camshaft was installed to control all the valve events of this engine. Designed for both power and great drivability while maintaining the full range of adjustment offered by the OEM variable valve timing camshaft phaser assembly, the Livernois camshaft profile is the result of significant testing and refinement.

The camshaft features an intake lobe with .595 inch of lift at the peak with 216 degrees of duration at .050 inch of lift. On the exhaust side, there is a little less peak lift, at .580 inch, but significantly more duration with 240 degrees at .050 inch. The lobes have a 116-degree separation angle, which keeps overlap down and helps maximize the boost from the positive-displacement supercharger.

Riding on the cam lobes are a set of Mopar Hellcat (non-MDS) hydraulic-roller lifters. A set of Trend Performance pushrods sits atop the lifters and actuates the factory HEMI rocker arm assembly. In order to maintain control of the valves, Livernois fitted one of its 6.2L/6.4L valve spring kits.

The kit includes 16 custom-spec’d valve springs designed to be good up to .700 inch of camshaft lift. They offer 160 pounds on the seat (with a 2.030-inch installed height) and 390 pounds of open pressure with a .630-inch-lift camshaft. Also in the kit are a set of titanium valve spring retainers to reduce the overall mass of the assembly, and 8mm triple-groove valve locks. The assembly easily handles the extra lift and RPM this engine will see.

Topping off the long block is a factory supercharger manifold combined with a 2.4-liter Hellcat IHI twin-screw supercharger that Livernois has gone through and ported, as well as added their own custom supercharger pulley as part of their S1025 package.

In addition to more boost from the supercharger, the S1025 package also allows the use of E85 through the addition of eight Injector Dynamics ID1300X 1,335 cc/min fuel injectors and a billet twin-pump fuel system. Typically, the S1025 kit on a stock 6.2L Hellcat produces in the neighborhood of 830 horsepower at the rear wheels. The question is, how much will it make with the new 401-cube long block?

On the Dyno

With the long-block assembled and installed into the car, the S1025 package from the OEM powerplant was reinstalled, and everything was broken in. Then, the Challenger was driven onto Livernois’ Dynojet chassis dyno and cranked up. The final results were quite impressive: 908 horsepower at 6,540 rpm and 908 pound-feet of torque at 3,490 rpm.

The torque curve is an absolute beast and will be a riot on the street. The power-adding parts, coupled with the heavy-duty components and expert assembly that Livernois is known for, make for a powerful combination that should live indefinitely. By hunting for reliability as much as a power number, Livernois has engineered a complete solution for Gen-III HEMI-powered vehicles.

Livernois 401 Cubic-Inch Gen-III HEMI Top End

• Cylinder Heads: OEM 6.2-Liter Hellcat castings
• Porting: Livernois Stage 3 (Race Port) package
• Port Flow: 386 cfm, intake; 242 cfm, exhaust – both at .600 inch of valve lift
• Valves: Custom Manley valves
• Valve Springs: Livernois 6.2L/6.4L Valve Spring Kit
• Locks/Retainers: Livernois titanium valve spring retainers with triple-bead locks
• Rocker Arms: Factory Gen-III HEMI
• Lifters: OEM Hellcat non-MDS hydraulic rollers
• Pushrods: Trend Performance
• Camshaft: Livernois Hellcat Stage 2 VVT; .595/.580, 214/240, 116 LSA
• Injectors: Injector Dynamics ID1300
• Power Adder: Livernois-ported OEM 2.4-liter IHI twin-screw supercharger
• Ignition: Stock
• Fuel: E85
• Fuel System: Livernois billet dual pump system