Over the course of its 11 years in existence, the X275 drag-radial category has transitioned from a relatively affordable — emphasis on the world “relatively” — mid-level heads-up program to one in which any stone left unturned will relegate you to also-ran status and obscurity.
Four years ago, we embarked on a new goal of competing in X and the NMCA/NMRA Street Outlaw classes with our “Project Evil” Fox-body Mustang, which we’d previously campaigned in 8.5-inch tire classes. A supercharged small-block Ford engine was built by KBX Performance, and all the great parts and pieces necessary to run competitively were assembled. The car ran well, no doubt, even going rounds at DuckX Productions races, but as an older chassis, it wasn’t built entirely with modern-day X275 competition in mind. In other words, the class had kinda’ passed it by.
As we turned our attention to the build-up of “Project BlownZ28” over the winter and subsequently got it on the racetrack, it created an opportunity to park “Evil” for a while and give it a much-needed makeover. Keith Engling, better known as the “skinny kid” behind Skinny Kid Race Cars, did a bang-up job on BlownZ28 — as he’s done for countless other racers over the years — and so who better to turn to to get the Mustang in fighting shape for a class that is running in the 4-teens.
Our primary initiative in the offseason was to shore up the chassis — focusing on stiffening it up with a double framerail upgrade and providing ourselves with more rear suspension adjustability. Eventually, the opportunity presented itself to be among the first racers in the class to debut a brand new X275-spec supercharger from the gang at ProCharger — and thus, this turned into quite the overhaul. But the juice is worth the squeeze, we believe.
Let’s get up to speed on where “Evil’s” been.
Chassis Upgrades With Skinny Kid
Engling and company spent a lot of time on Evil’s chassis and body over the winter — working from the center to the front and the rear. The primary area of focus was on the aforementioned double framerail addition.
“The double frame rail, especially in a car like this, is to support the engine. It just locks the engine into the chassis better,” Engling begins. “Since it’s a stock suspension car, it’s less about supporting the chassis, because the rear suspension isn’t hooked up to it. But it’s mainly to keep the car from twisting…it’s tied really hard into the mid-plate, and the mid-plate is what does all of the work, not the front motor plate.”
Skinny Kid had to cut the mid-plate mounts out of the chassis and redo them. The top frame rails then come to a head just forward of the firewall; Engling then installed -16 fittings to run the burn-down tubes out of the valve cover breathers and direct the engine blow-by through the chassis and out through the rear of the car via an air-oil separator.
Staying up front, unnecessary OEM steel material was removed from around the shock towers to ease servicing of the spark plugs. While we’ll hit on these points in more detail in a bit, a ProCharger RaceDrive supercharger gear drive unit was installed out in front of the engine (requiring Engling to move the rack-and-pinion steering box), while a new Wilson billet intake manifold was outfitted to the top of the 441-inch small-block Ford mill.
Engling fabricated a complete set of 2-3/8- to 2-1/2-inch stepped “zoomie” headers, as well. With so many changes needed up front — clearance at the cowl for the intake, an inlet in the front for the ProCharger, and a slot to route the headers, it was simpler to start with a whole new carbon-fiber nose from Schoneck Composites.
Engling mounted the new nose, and got to work fabricating a very clean-looking inlet in the bumper that transitioned down to the size of the supercharger volute.
The zoomie headers adhere to engine and chassis characteristics that Engling and others discovered long ago with their supercharged race cars.
“Zoomies on a supercharged car allow them out-sixty-foot any other car…because of the downforce that the zoomie creates,” he explains. “We can leave harder without having wheelstand problems. On my car, with a screw blower, the front suspension compresses almost 3/4-inch just by going up on the chip on the starting line. There was a long period of time where people said exhaust velocity doesn’t do anything, but they’re completely wrong. We learned that way, way back, even with turbo cars. That’s why we had “bullhorn” exhaust on V-bands, so we could point them up depending on track conditions.”
The engine position fore/aft was retained, but Engling took the liberty of adjusting the pitch of the small-block to ensure it’s pointed at the pinion. He went on to explain this further, displaying his many years of chassis building and tuning prowess.
“It’s critical that the engine points at the pinion at ride height. It comes down to the physics of it….surging and vibrating of the car as it’s going down the racetrack. If the engine and the pinion aren’t parallel, the driveshaft is going to surge, which can then create vibrations. You have to have 1.5- to 4-degrees of a “V” between the pinion and the driveshaft for the car to work properly; so that determines the angle of the pinion.”
“If the engine is in the car wrong, it’s impossible to make the engine and the pinion parallel with the correct pinion angle in the car. You can adjust pinion angle, but you can’t adjust the engine once it’s in the car. Engines are often left in the stock location, but once you lower the car and put bigger tires on the back, the engine is pointed below the pinion; if anything, the engine pointed above the pinions better than below it.”
The dramatic rear shock extension event, of course, can wreak havoc on the engine-to-pinion relationship, as the engine raises with the body at launch and going down the racetrack.
“We do the setups based more on where the car is at extension, because that’s where it goes down the racetrack,” Engling says. “So we calculate that out to where it’s going to be most of the time under power.”
Taking that a step further, a new full-floater fabricated rearend housing was acquired from Merillat Racing, with a slew of upper and lower pickup points to amp up the degree of adjustment, and more importantly, for the safety of the floater design. Out back, matching new upper and lower torque boxes to the floater housing were installed from Merillat Racing to give Skinny more control arm pickup points for added adjustability. As per the X275 rules, these were placed in the stock location.
Finally, Engling flush-mounted all of the windows, also utilizing Schoneck Composites’ carbon-fiber quarter windows to give it a racey look.
Callies “Ultra Boost” Crankshaft
The team at Callies has an impressive product in its Ultra Billet lineup of cranks — made from a 4340 alloy, Callies intended these cranks for high-horsepower applications where durability is paramount. This was accomplished through the use of specialty steel and heat treating processes to create fracture resisting ductility and a wear-wear-resistant casing.
Callies has now taken its Ultra Billet cranks a step further with the new Ultra Boost, which are designed specifically with turbocharger and supercharger applications in mind. Callies used its proprietary 4330 TimkenSteel material on these, and the pin arms mimic those used in its ultra-strong Top Fuel crankshafts. Extra material has been added to the front and rear arms where the loads are targeted and typical fail in a boosted application. Overall weight, however, has been reduced from the Ultra Billet, allowing the engines to turn higher RPM without increase risk of failure.
New Gadgets From ProCharger
All of that boost to go along with the Callies Ultra Boost crank comes compliments of ProCharger’s new F3-102R supercharger — a hybrid containing parts of two proven, existing units.
To create the 102R, ProCharger mated an F-3 gearbox to an F-1X impeller, creating both a powerful and reliable unit — one that Rob Goss has already driven to the X275 world record in its short time.
“The F-1X impeller has been around forever, as have the larger compressor housing and larger gearbox….for six years we’ve wanted to use the larger gearbox with the F-1X, because guys were having to push them so hard to make the power needed to compete in the class that they were breaking the superchargers,” explains ProChargers’ Erik Radzins. “So for a long time, we were asking to have the F-3 gearbox attached to the F-1X impeller and could never get it approved. It’s just marriage of things we already had, to make it durable. Are guys going faster with it? Yes, but that’s because they have more confidence now in leaning on it.”
Driving the 102R is a ProCharger Crank Drive, a front-mounted, crank-driven unit that allows for maximum efficiency in extremely powerful engines. The CrankDrive allows for a number of accessory drive units, and the gear set are easily swapped. The CrankDrive also positions the supercharger higher in the car for clearance of steering and other chassis components.
Wilson Billet Manifold
Wilson Manifolds has long been regarded as a leader in the development of high-tech race intake manifolds, and if we wanted to run at the front, Wilson was the place to call. After sharing the nitty gritty details — RPM, vehicle weight, horsepower, how many times the car shifts, stall speed, converter fall-back, and so on — Wilson went to work and designed and machined a forward-facing, billet intake catered specifically to the supercharged small-block Ford and Bennett cylinder head combination.
Keith Wilson explains that there’s much more science to an intake manifold than simply making it “big enough.”
“A lot of people think with a blower or turbo that the design is irrelevant, but it’s totally opposite of that. It’s very important to make as much power as possible, and then add your power adder. We do pay attention to runner length, taper, plenum volume, and so on. We also work to get even balance between all eight cylinders, so you’re making the same cylinder pressure in each cylinder. Because you can have a cylinder making 200 horsepower and another is making 150, and the engine is in a fight with itself, so we pride ourselves in getting the distribution really close, even on a high-horsepower, boosted application,” he says.
Wilson says it’s these efforts to look at the whole application and design the heads, the engine, and the intake as one unified package that allows the car to accelerate quicker. “We tailor this to the customer and the applications, and that’s why our stuff runs so well,” Wilson says.
Wilson also machines its own fuel rails, using a patented “D” shape with a flat bottom to help the fuel flow more efficiently than a round circle. The 123mm throttle body, like the intakes, is designed to be robust — the unit on Project Evil is a tried-and-tested product that Wilson customers have relied on for years, sporting a 1/2-inch, unsealed, brass plate blade. Not ones to rest on their laurels, though, Wilson has continued to develop and evolve its products, and will soon have a newer 123mm throttle body with a 5/8-inch split shaft and a 70-series aluminum tapered blade (to retain flow despite the larger shaft).
Beyond all of its technical features, this intake just looks stunning, too, doesn’t it?
Full Floater Housing with Strange Internals
SKRC frequently sources rearend housings from Merillat Racing, a fabrication business owned by Marty Merillat. Engling then finishes the housing to his specifications, but because SKRC doesn’t frequently build stock suspension cars, Engling sourced a complete housing from Merillat, to meet our goal of switching to a full floater-style housing for the purpose of safety.
“Keith got with me about doing a floater housing and kit for the car and I was happy to be onboard. The housing is designed and welded in house, and we add a clear powdercoat that we put on all of our housings,” Merillat says. This clear coating allows you to see the welds and individual components
The housing has a .500-inch thick faceplate for added strength, and considerable adjustment top and bottom is available with Merillat’s custom upper and lower control arm brackets. We sourced a set of full floater axles from Strange Engineering to finish out the rearend assembly, using the Strange center section that we already had in the car last season.
In a full floater, the weight-bearing is placed on a spindle that’s welded onto the axle tube of the rearend housing, with the spindle itself and a set of bearings that ride on the spindle supporting the weight. In effect, this separate the load-carrying and the torque delivery roles of an axle so the axle’s only job is to transfer horsepower and torque to the wheels. For high-horsepower applications, this prevents the possibility of the axle flange breaking.
As part of the conversion to a full floater rearend housing, we hooked up with Strange Engineering for a set of full floater-specific axles (Part# A2040M24) — these 40-spline, gun-drilled parts are made from extremely durable gun-drilled 300M material, a modified 4340 steel that contains silicone, vanadium, higher carbon, and molybdenum. These axles are a preferable choice in heavy cars with 3,000 or more horsepower, and Radial vs. The World cars have utilized them frequently.
These sport a .875-inch I.D. hole bored the entire length of axle, hobbed 40-tooth spline count with a 45-degree pressure angle on both ends, involuted splines provide full surface contact area, and are heat-treated and thru hardened for hardness, ductility, and torsional strength.
To compliment the axles, we’re utilizing Strange’s 40-spline, full floater steel rear brake kit (Part# F22065). The 4130 chrome-moly spindles are machined with large inner bearing radius for added strength; the aluminum hub/rotor adapters are made from a 2024-T351 billet aluminum, and the lug design allows rotors to float; the stainless steel Spindle Radii rings create a positive inner bearing seat and provide a corrosion resistant sealing surface.
The stainless steel rotors (Part# F2056NL/F2056NR) are machined from a highly warpage resistant steel and sport directional slots; in addition, the four piston billet aluminum calipers with stainless steel pistons are rigid and lightweight.
With the heavy lifting of fabrication complete, Evil is now off to the body shop, where it will be sprayed in a PPG Vibrant Collection ‘Kilauea Glow’ — the very same shade of orange seen on its sister car, Project BlownZ28. It will then head back to SKRC for assembly, its engine installed, and everything wired and plumbed so we can hit the ground running in the second half of the season. As soon as the paint’s dry and Evil is back rolling on its own four, we’ll share some images of the final product. Stay tuned!