If you’ve been keeping up with our questionable financial decisions, you may have noticed that we recently acquired a Fox Body Mustang with a bit of grudge racing history. Our ambitious objective? Transforming this Fox Body from a mere street racer into a bonafide Ultra Street contender. While conventional wisdom might have led others to invest in a turn-key car or, at the very least, an ex-Ultra Street rolling chassis, we opted to cut costs by buying one without the pedigree behind it. Maybe a mistake, but it allowed us to completely overhaul the chassis to our likings before slotting an engine into its tubular front end.
With our chassis work successfully completed, we needed to enlist the expertise of professionals to build our engine. While we’ve taken on numerous engine builds, claiming to have constructed anything of Ultra Street caliber would be akin to boasting about flying spaceships when, in reality, we’ve only ignited a few fireworks — with an ending we’d rather not replicate on our engine. Achieving the level of performance required for Ultra Street demands knowledge, precision workmanship, and a lot of nice tooling behind it. Thankfully, with great friends like Jon Bennett of Bennett Racing Engines and John Kolivas of KBX Performance, it only made sense to leverage their skills to our advantage. In this segment, we’ll be covering the short-block and what is required to build a race-winning engine according to Jon Bennett.
The foundation for any engine build begins with the block. For any 9.5-inch-deck small-block Ford build, Bennett uses a Carroll Shelby Engine Company block. The cast-aluminum solid block has more rigidity than its coolant passageway-equipped counterpart and has been proven to withstand the abuse seen in grudge cars running 3.9-second 1/8-mile passes to X275 cars running in the 4-teens.
However, these blocks are taken a step above once they arrive in the hands of Bennett Racing. “We take the block as supplied by Shelby through many machine processes. It is bored and honed with torque plates to a final bore of 4.125-inches, align honed, sleeves set, and lifter bores taken from the stock diameter of .875- to .905-inch, allowing us to use a more durable lifter,” Bennett explains. ‘We then make proprietary modifications to the oiling system of the block, clearance for rods, and groove the sleeves for our fire-ring head sealing system. Finally, we clean the block for final assembly and install the 55mm roller cam bearings.”
Now, you might be asking, “Is Bennett really using a block with only a two-bolt front main cap?” The short answer is yes. Bennett states, “We have never seen a main bearing issue on these blocks, and we have had customers run for years straight without failure, making big power
The next piece of our engine build revolves around the crankshaft. For this, Bennett used a Callies Magnum crankshaft. “The Callies Magnum crankshaft is the preferred choice for Ultra Street builds,” says Bennett. “We also use the Ultra Billet Callies crankshaft on engines that are ultra-high-power engines and supercharged engines. The main advantage we see with these cranks is the center counterweights.”
For our build, Bennett chose a 3.75-inch stroke with a 2.100-inch rod journal size. “The choice of a 3.75-inch stroke is based on power adder restrictions, fuel used, and other design components of the combination. This stroke, paired with the 4.125-inch bore, yields a 400 cubic-inch engine,” Bennett explains. “Once the crankshaft is balanced, we polish and clean for final assembly.”
Bearing The Load
The next crucial component are the rod and main bearings. Since the connecting rod bearings experience the brunt of combustion, ensuring their capacity to handle this load is essential. Bennett’s bearings of choice are the Calico Coated bearings. However, the process involves more than just installation. “Before installing the crankshaft, we place the main bearings, torque the main caps, and employ a dial bore gauge to determine the bearing housing bore size. We follow the same procedure for the connecting rods by fitting a rod bearing in them and using a dial bore gauge to determine the housing bore size,” Bennett explains.
Bennett continues explaining the process, “We then use a micrometer to check the crankshaft’s main and rod journals, obtaining measurements necessary to establish bearing clearances. Based on these measurements, we selected P/N: MS1010HX main bearing. The ‘X’ in the part number indicates that this version provides an additional 0.001 inches of oil clearance. The rod bearings chosen were P/N: 663HXND. These bearings also feature an ‘X’ in the part number for the same reason, but they additionally include a ‘D –’ the ‘D’ signifies that the bearing has a dowel hole for use with aluminum connecting rods.”
Connecting The Parts
Moving up the rotating assembly, Bennett chose GRP connecting rods. “GRP’s part number 1201 is a severe-duty small-block aluminum connecting rod with the ability to handle huge power levels.” Although not required for our engine, Bennett notes that GRP connecting rods offer various options, including cam and counterweight cut options. The cam cut option adds clearance to the big-end of the rod to provide more rod-to-cam clearance, while the counterweight cut option creates more space under the pin bore for crankshaft counterweight clearance.
“Due to the sheer volume of engines we work on, our standard align hone spec number, and our excellent rod choice, GRP consistently builds reliable parts,” Bennett explains. “We determine the bearing specifications required for the mock-up after checking the crankshaft. Typically, our main and rod bearing clearance averages 0.003 inches on these engines.”
Diamonds Are A Blocks Best Friend
Crowning our rotating assembly was a set of Diamond Racing Pistons. “The Diamond Pistons’ design features a piston dome made specifically for our Trick Flow Specialties 265 cylinder heads (a topic that will be covered in the next article). They feature horizontal gas ports, a hard-anodized coating, and a .990-inch pin bore,” Bennett explains. “The final piece to the puzzle is choosing the correct piston pin. In this case, we opted for a .200-inch wall-thickness pin. While it may seem like overkill, it provides users the option of installing a larger turbo on the engine without worrying about piston pin failure.”
“Piston size is a common issue we encounter in many engines we rebuild that were not originally built by us, with too-small of a pin being used. Piston pins typically come in a .150-inch wall-thickness, which is sufficient for low-power engines with minimal boost or low nitrous amounts,” Bennett explains. “However, when you start surpassing the 1,000 horsepower mark at the flywheel with a power adder, the pin choice becomes crucial to ensuring a happy piston.” Bennett adds, “The majority of our .927-inch-pin engines are equipped with a .225-inch-wall pin, while our .990-inch pin engines use a .200-inch up to a .240-inch-wall pin, depending on boost levels and the type of fuel used. M1 engines will always receive a larger wall pin due to the increased fuel volume in the cylinders.”
Total Seal Rings In The New Block
Rounding off our drivetrain was a set of Total Seal piston rings. “Total Seal piston rings are the rings of choice for our engines, specifically their AP Stainless variant. These are sized at 1/16-inch for the top ring, .043-inch for the second, and 3mm for the oil ring. We file-fit these to a specific gap size on top that we have developed, believing it works best and allows the ring to hold up throughout the season.”
The attention to detail doesn’t stop there. Bennett continues, “We pay close attention to the oil ring, particularly its gap. Many people overlook checking the oil scraper gap, often using too wide of a gap on the scraper, which can lead to oil control issues in the cylinder. In manycases, if you purchase a 4.125-inch oil ring, the scraper gap will be too wide, necessitating a move to 4.130-inches, and, in some cases, filing the scrapers.”
Our Short Block Is Complete
As you might have figured out by now, Bennett does not take shortcuts, and his attention to detail can be seen throughout this build. His knowledge of where the stress lies in a high horsepower engine and how to alleviate it through stronger parts or proper sizing is extraordinary. It’s no wonder that the fastest Ford racers in Ultra Street are running Bennett-built racing engines. Stay tuned for our next installment, which will cover the cylinder heads.