g-Force Hemi

Some guys just have a driving ambition for the one-upmanship and achievement in building "The ultimate" g-Machine. When you consider it, it's a tall order. In the realm of street performance, the goal of the g-Machine has "the ultimate" wrapped up in it by definition. Unsurpassed handling, roadabilty, acceleration and balls-out power are the hallmarks of the g-Machine scene. Attempting to render the ultimate incarnation of the g-Machine is really striving for the ultimate of the ultimate. Bob Johnson is driven towards this goal, and has expressed that ambition through some serious g-Machine project vehicles in the past. His previous efforts have been featured and acknowledged in these pages. (See Bob's '69 Camaro called "Battle Axe," in Jan '04. It was our cover car that month.) Bob's latest endeavor lead to what may be the Holy Grail of the Mopar g-Machine: interpreting Mopar's most desirable musclecar body style, the 'Cuda, as the ultimate g-Machine. Bob teamed up with car builder Alan Johnson (no relation) to craft the concept into reality. The team of Johnson and Johnson were looking towards pushing the envelope far beyond the normal consumer goods, taking their crack at the "The ultimate g-Machine." The finished vehicle will be featured in PHR as an exclusive once it's completed, but those wanting a sneak peak will be able to check it out at the 2005 SEMA show in Las Vegas Starting November 1. Be Forewarned: Don't expect it to be a pampered show car. Bob Johnson's g-Force 'Cuda will be driven hard-hard enough, we expect, to set a new record for a street car going from 0 to 100, and back to 0. That takes a lot of gs (in more ways than one).

Function, form, and most importantly true performance, all integrate into a project this ambitious. Alan's Art Morrison-based chassis will debut with significant engineering, from the custom tube chassis, and one-off all independent coil-over sprung suspension, Baer six-piston disc braking system, massive Michelin PS2 tires, and custom Getrag transaxle. No stone will be left unturned in incorporating the hardware to meet their goals. Of course, topping the list of required machinery for a project of this sort is a suitable powerplant. For this Mopar, Indy Cylinder Heads was the natural choice.

Indy Cylinder Heads (ICH) is a name well known to Mopar fanatics the world over. No one has taken the mantle of Mopar engine performance and gone the distance in the way the organization at ICH has. A milestone for ICH founders Russ and Fred Flagle, was a pioneering move into aftermarket aluminum heads for the Mopar wedge engine introduced decades ago. From this, Indy has grown to design and manufacture Wedge, and Hemi engine components that define contemporary Mopar performance. Indy manufactures blocks, intakes, heads, and many more components that propel the original Mopar engine architecture to power levels, and configurations unheard of back in the original musclecar days.

For the Johnsons' project, the Hemi engine would provide the presence and persona of pure power that would help define the 'Cuda. Hemis are no strangers to power production, but in a g-Machine application the sheer mass of the engine would disturb the delicate balance that the builder was looking to achieve with the vehicle. Here, ICH provides the answer in their aluminum Maxx block. Using the Maxx as the basis for the powerplant opens the door to a near ideal situation. Indy's complete all-aluminum Hemi makes for a lightweight package, tipping the scales at a small-block-like 535 pounds. Low mass is nice, but the powerplant is advantaged further by the sheer strength and capacity possible with the Indy Maxx block. Indy can, and routinely does, build these engines in displacements of 655 plus ci, and the power handling capacity are off the scale. Indy's hardware makes the notion of a lightweight, big inch, high-powered and reliable Mopar engine a reality.

But the high-g nature of Indy's g-Force Hemi doesn't end with lightweight. In order to achieve the ultimate balance for handling, car builder Alan Johnson made the decision to position the Hemi rearward and lower in the engine compartment, thus setting into motion some rather significant design requirements for the engine, body, and drivetrain. Rearward location of the g-Force Hemi meant using the aforementioned Getrag rear transaxle, but it also meant using a dry-sump oiling system. This allows for superior oil scavenging under hard cornering loads, and it also improves the vehicle's center of gravity by allowing the engine to be much lower in the chassis. Yes, it sounds odd, but the Indy g-Force Hemi is an engine that-when integrated properly with the chassis-actually improves handling.

Zeroing in on the exact combination for this project was a collaborative effort with input from the vehicle builder providing the objectives that needed to be met. Making more than a useable amount of power would be no problem based on the resources at Indy, however the Johnsons imposed constraints. The engine would above all need to meet the requirement of real streetabilty. This is defined by the requirements for reliability in long-term street use, a reasonable, if not tame idle quality, and the ability to swill normal pump gasoline without balking (although just barely!). With the massive reserves of power potential in the Indy Legend line of aftermarket Hemis, meeting these goals, while producing unnerving output was the task of Indy's chief engine builder Ken Lazzeri.

Ken took the "conservative" approach, knowing that by scaling back the combo of one of Indy's race-spec'd mills, the drivability, low-maintenance and reliability objectives could be easily met. At the same time, with a relatively large displacement and just enough cam, compression and cylinder head, the output would remain dramatic. Although the engine, with a bore and stroke of 4.50 inches displaces 572 ci, by Indy's standards this is a conservative displacement. In a street application, it would be hard to argue that 572 cubes would fall short of delivering all the torque a car could manage. Low-end torque is what you'd expect, but what comes as a surprise is the high rpm characteristics of this mighty Hemi. Power just keeps coming on, a testimony to the outstanding matching of the combination's components, and the phenomenal flow of Indy's Windjammer CNC-ported heads. The bottom line: what we have here is a 572ci Hemi that weighs-in and revs like a small-block, while belting out more torque and power than most street freaks could imagine. If like Alan and Bob Johnson, you are looking to build up the ultimate, here in detail is what Indy did to make it come together.

We were asking a lot when we approached Indy to build the ultimate g-Machine engine. Just make it a Hemi, only about 150 cubes bigger than a stocker, but make it weigh less than a small-block. Make power like a serious drag motor, and make it run smooth and reliably on the street in full-out open-road race competition, on pump gas, please. Easy, huh?

The backbone of our Indy-built g-Force 572 is an Indy 10.720-inch deck aluminum Hemi Maxx block. With a capacity to easily accept a 4.50-inch bore and the weight savings of aluminum, the Indy block is the basis for huge power in a lightweight package, just the one-two punch we needed for our ultimate g-Machine mill. The Maxx blocks are fully CNC machined at Indy from a bare casting of Indy's design.

The block's finished bore size of 4.50 inches is matched with a 4.50-inch stroke Callies 4340 forged steel crankshaft. The rod journals are undersized at a big-block Chevy spec of 2.20 inches, reducing bearing speed and increasing stroke clearance in the crankcase. The Eagle 3D connecting rods measure 7.10 inches and are sized for the Chevy 2.20-inch crankpin, and likewise accept a 0.990-inch Chevy big-block piston pin at the small end. Pistons are Wiseco small-dome forgings as spec'd by Indy, and weigh-in at 755 grams. The combo provides a rod ratio of 1.58:1, very reasonable for such a long-armed crank-got to love that tall block deck that makes it possible.

Taking advantage of coating technology, the pistons for this build were sent to the experts at Swain Technology for thermal barrier coating of the crown, and an anti-friction coating to the skirts. Hemi engines have considerable piston surface area which presents a challenge to thermal inefficiency. The thermal barrier helps retain combustion heat with the goal of adding power through greater efficiency. By the same token, stroker engines will present greater thrust loading and rod angles than short-stroke engines. Friction-coated skirts help put the slip to friction at the source.

Note the deep intake valve relief and low top ring placement of the piston. Indy has these packages worked out to a science, and the considerations in putting together a working combo are pretty complex. If you're building a monster Hemi on your own, you better be prepared to work out all of these detail, like ring placement, dome height, valve relief depth, location, and a lot more. Trying to get it right on a one-off custom build can be pretty tough, or you can skip the guesswork, trial and error, and let Indy's experience with these combos work for you.

If serous power output is the goal and keeping it together is also part of the plan, you simply cannot go slummin' in the maincaps. Big strokes, high rpm, and big power and torque brutalize the bottom end. Stock Mopars will walk the maincaps at moderate power levels. These Indy blocks are designed with integrated billet steel maincaps in mind. The cross-bolted caps tie the entire lower structure of the block into a "bridge" which, combined with the massive lower-block bulkheads, provides an anvil-tough structure. Cross bolting eliminates the cantilevered structure of a standard-style cap, and is possible only in a deeply skirted block as in a Mopar Hemi or Wedge.

With the crank and mains installed, it's easy to see how the structure of the lower block is securely tied together. Note the stroker clearancing done to the lower cylinder walls in the crankcase. Indy has worked out the programs for their popular applications making the clearancing a routine and foolproof CNC operation.

Indy's Maxx block is fully water jacketed, and designed for both street and race applications. The cylinder walls are centrifugal-cast sleeves, which are a dry-sleeve configuration in the block. This provides the best in bore stability, rigidity of the decks, and reliability in long-term operation. Notice also the beefy ribbed lifter valley and high-strength Indy-sourced head studs. Get the idea that the guys at Indy aren't fooling around? The engineering is first-rate.

Driving the camshaft is an Indy Rollmaster billet gear timing set. With the roller cam, thrust must be controlled to keep the cam located properly in the block, a task accomplished with a thrust button clearanced to work with Indy's No. 440-22 aluminum timing cover. Also, at the front of the engine Indy employs a premium ATI Super Damper, No. 917475 E, regarded as one of the most effective in the industry at controlling crank harmonics.

The camshaft is a Comp No. CRH 300-7-295-4 R110 (measuring 268/264 at 0.050-inch and with 0.650/0.630-inch lift), may seem "big," but with 572 ci soaking it up, the combination is more than docile enough to work well on the street. Engine builder Ken Lazzeri considers it "mild"-and it is, compared to the full-race combos put together by Indy. Ken described the idle as "smooth." The roller lifters are Comp No. 829-16, while the springs are Comp No. 26115-16, delivering 210 pounds of load at 2.10 inch. The tall installed height, and moderate spring loads provide longevity and control. Comp titanium retainers help lighten the weight load at the valve, and are 10-degree units for use with Comp's 10-degree SuperLocks.

Ken precisely degrees-in the cam in every engine Indy builds. For this engine, the camshaft was phased at 105 degrees installed intake centerline, which is 5 degrees advanced with the camshaft ground on a 110-degree lobe separation angle. With an installed intake centerline of 105 degrees, and the shorter exhaust lobe, exhaust overlap is reduced and trapping efficiency is enhanced, helping to further tame the large stick.

With the cam timed in place, Ken moves on to installing the pistons. The rings, No. R10451-45, have already been sized to the bore for an end-gap of 0.024-inch top, 0.028-inch second. This is in keeping with modern ring theory on ring end-gaps, opening the second gap larger than the top to reduce the chance of ring unloading due to trapped pressure in the ring pack between the compression rings. A tapered ring compressor allows the piston assembly to slide into the block with a minimum of persuasion, and is a tool worth having.

With the g-Machine aspirations of this engine build, the sump and lubrication system had to meet some specific requirements. Oil control under acceleration, braking and cornering were vital, while reducing windage losses and controlling the oil were also important considerations. Under road-race style demands, nothing will compare with a dry-sump system so that was the system selected for our g-Force Hemi. The four-stage gear-driven Missile dry sump pump system is a thing of beauty, operating in the Hemi application without the need for cogged drive belts as with most dry-sump applications. The Charlie's dry-sump pan offers excellent windage control and a much lower profile than a deep wet-sump pan. This will be a big aid in getting the engine set as low as possible in the chassis, benefiting ground clearance as well as allowing a lower center of gravity.

The Indy-manufactured aluminum block provides the foundation for this engine, and the Indy cylinder heads open the potential for the bottom-end to develop huge power. As with the blocks, the heads are Indy's own castings and are machined in-house on precise CNC equipment. The heads for our build are Indy's Legend, part No. 426-1 RA.

Indy's Windjammer cylinder head porting is also done via an automated CNC program and the results are impressive. Intake port flow pegs the scale at 510 cfm, with an intake port volume of 295 cc. Intake port volume is critical to power production and keeping up with demand as rpm rises. A combination of high-flow and sufficient port volume is what it takes to extend torque production up the rev range, and really making use of the power output a large displacement engine can develop.

Looking down the cavernous intake ports, there is little in the way of moving copious quantities of air directly into the cylinder. Intake valves measure 2.40 inch, while the exhausts measure 1.940 inch.