Grunt, Oomph, Twist. That's real power.
Power is what Mopars are known for. At the root of that power, the key to wheel-lifting launches and asphalt-rippling burnouts is torque. Torque is also what defined 1960s muscle cars. While today’s four-valve, DOHC, fuel-injected vehicles offer performance, you don’t hear much about torque--nor do you feel it. Today’s high-revving, light-switch-for-power engines are super-efficient, clean burning, and high-revving. But they lack pin-you-in-your-seat power that forces you hang on when the pedal hits the floor. Heck, in some cases, a torque monster doesn’t require even moderate accelerator pedal travel. Perhaps that is why when Holley chose to build ten project cars--one from each decade of the company’s existence--there was no question that the automotive selection for the decade beginning in 1960 would be a big-block Mopar. Holley Performance Products and its brands including Lunati, Hooker, Earls, Holley Superchargers, Weiand, and Nitrous Oxide Systems all have an affinity with large cubic inch, V8 muscle. The choice to go with a Mopar for a decade as important as the 1960s is significant commentary regarding whose muscle cars made the most power consistently.
Torque is the back-to-basics commentary--but how would one add a twist of today's trends. When Holley approached us about their Project Roadrunner, they asked who we thought should engineer the Mopar-specific powertrain combination. Certainly, the answers could range from a crate Wedge or Hemi from Mopar Performance Parts, but that might reduce the potential content of Holley brands in the engine assembly. With the goal of exhibiting Holley's brands, we suggested that Indy Cylinder Head be the engine builder. With their loyalty to the Mopar community--displayed in their long list of products made specifically for Mopars--as well as their far-reaching reputation, we knew that Indy would be the place to go. Holley agreed--in fact they had already come to the same conclusion prior to our suggestion. Holley would look to Indy Cylinder Head for the gospel according to Mopar big-block power. In the early discussions with Ken Lazzeri of Indy Cylinder Head, it was apparent that there were several options--maybe a mid 400ci low-block stroker or perhaps a huge displacement 440-based RB. The intended use is what helped to make the final decision of which displacement big-block Mopar to build.
The Holley Performance Products Project Roadrunner would be a street car. Sure, it might do a quarter-mile once in a while, but primary use would be cruising--even long distance Hot Rod-style Power Touring. This Roadrunner would be four-speed shifted backed up by the stoutest Hemi A833 possible, yet produce enough torque that you could basically leave it in Third all the time. Lazzeri told us, "We have built many 500ci pump gas engines and they were capable of 600 to 610 lb-ft of torque and nearly equal horsepower--in street compression. Additional displacement was the key to building a torque monster." Ken also knew that a bit more displacement may pull down the horsepower figure, but the torque would rise exponentially. "When you try to create a torque monster on purpose, the equation is fairly simple--moderately high velocity heads and a relatively small camshaft. You sacrifice peak horsepower." Sacrifice horsepower? "Heresy," you say. Ken continues, "The reality is that building high-torque engines puts horsepower on hold. Our goal was torque first." Remember, horsepower is a function of torque. The polar moment of inertia happens sooner when the fulcrum favors the power source rather than the object to be moved.
You get more torque with a bigger stroke and the benefit of that higher displacement is that torque is anticipated. When you couple it with a mild camshaft, moderate compression, and street hardware, you get the maximum reliability, very smooth running operation, and in our case, over 575hp. For those of you who are counting, that's still more than one horsepower per cubic inch. That, with a mere 9.5:1 compression--it'll run on any gasoline in the world. Best of all, while premium components are used, the engine internals are far from exotic. To gain the torque figures that would test transmission and the abilities of driveline components, Ken proved that it can be done with off-the-shelf parts. To gain high-horsepower at the sacrifice of torque, even larger heads, race compression, and radical roller cams would get this same displacement right up to the 800hp. But torque rules the street.Grunt, Oomph, Twist. That's real power. Power is what Mopars are known for. At the root of that power, the key to wheel-lifting launches and asphalt-rippling burnouts is torque.
Torque is also what defined 1960s muscle cars. While today’s four-valve, DOHC, fuel-injected vehicles offer performance, you don’t hear much about torque--nor do you feel it. Today’s high-revving, light-switch-for-power engines are super-efficient, clean burning, and high-revving. But they lack pin-you-in-your-seat power that forces you hang on when the pedal hits the floor. Heck, in some cases, a torque monster doesn’t require even moderate accelerator pedal travel. Perhaps that is why when Holley chose to build ten project cars--one from each decade of the company’s existence--there was no question that the automotive selection for the decade beginning in 1960 would be a big-block Mopar. Holley Performance Products and its brands including Lunati, Hooker, Earls, Holley Superchargers, Weiand, and Nitrous Oxide Systems all have an affinity with large cubic inch, V8 muscle. The choice to go with a Mopar for a decade as important as the 1960s is significant commentary regarding whose muscle cars made the most power consistently.
Ken and the crew at Indy Cylinder Head started with Mopar Performance Parts' cast iron street RB block (P4529851). Termed a water block, it maintains water flow between cylinders for the demands of street use as opposed to the siamesed bore offerings. Siamesed-bore RB blocks can be bored to 4.500-inches. As received from MPP, the "water block" maintains the stock 4.25-inch bore diameter; however, Indy Cylinder Head opens it up to a 4.375-inch bore--which is "the largest bore diameter this cylinder block can accommodate," according to Ken Lazzeri. All of the MP RB blocks have the stock 10.72-inch deck height. | 
Indy's capability as a full-service engine builder extends from their own block and cylinder head designs and castings to their seven large CNC machining centers for customer-specific machine work, as is shown here. The same processes used on their own line of Indy Cylinder Head products are also applied to Mopar Performance blocks like the one used in this 542ci application. | 
Specific machine work for the 542ci combination includes clearancing the lower skirt of the bore for rod clearance on each cylinder. The CNC's precision work guarantees exactly the same results every time. |
Because Ken chose to accommodate the use of a Lunati crank in this application, additional clearancing near the original location of the internal oil pickup required that the pick-up be fed from the pan rather than the stock block location. The CNC work accomplished here shows the cross section of the block's original internal oil pump pick-up location and orifice leading to the stock external pump. | 
The popular P4529851 block features both the Hemi mounting pads and the Wedge motor mount ears. | 
When weight is a factor, Indy Cylinder Head also removes the Hemi motor mount pads to flush on their in-house CNC which results in up to a 45-pound weight reduction per block. |
Part of the effort in building the 542ci stroker RB engine for Holley Performance Products' Project Roadrunner was to further determine the feasibility of using a forged Lunati crank. The Lunati crank is formed from a "generic" forging--a die that would fit big-block Chevrolets, but could be used for any big block with the same bore spacing. The assumption was that this generic crank could also be used in other applications. Holley plans on a late-2000 release of an RB crankshaft for big-block Mopars. | 
Obstacles to making this work are apparent first from the view of the flywheel flange. For Chrysler automatic applications, we are uncertain what the results would be with the thicker flange when mounted to the torque converter. Clearances would require measuring. Four-speed applications like that of the Holley Roadrunner will have no problem with this situation. | 
Ken Lazzeri is quick to point out that the Lunati crank is made of excellent material, however, the forging die is that of a big-block Chevy design. As a result, the counterweights are too short. On a Chrysler-specific forging, the measurement from the bearing surface to outside edge of the counterweight is 2.400 inches as indicated by the dotted line in the photo. On the Lunati crank--shown here--the measurement is 2.200 inches. That .200-inches short is critical--especially as it relates to your wallet. It takes as much as $750 in balancing expense to add enough Mallory metal to the counterweights to balance the Lunati crank assembly. When using a standard Chrysler forging, that balancing expense would run approximately $250. |