When it comes to building custom performance engines, there are numerous choices in terms of what direction to take. For many, improving the OEM design theme is accomplishment enough, using replacement-style parts that offer to significantly improve output. For the likes of Nick Arias Jr., getting the most from an engine means starting with a clean sheet of paper, and then making the parts in accordance to his uncompromising all-out performance ways. As Arias likes to put it, “You can make a great street engine from a race engine, but you can’t make a great race engine from a street engine.” A case in point is the 427-cube Ford featured here. Using a hemispherical cylinder head conversion developed by Arias, the engine is capable of phenomenal output in a race configuration, while the same basic package can be built for reliable street duty with outstanding performance.

In the creation of the specialty hemispherical head conversion for Ford’s Windsor small-block, several factors came together that brought the idea into development. Arias clearly had the manufacturing know-how and the track record to make it happen, with Arias’ Hemi conversions for the Chevy big-block having achieved legendary status since its introduction in 1972. Among numerous other accomplishments and specialty engines, Arias also brought the world the incredible Arias 10.0-liter, a full custom engine design using hemi heads that saw dominance in tractor pulling and drag boats. The link to the Shelby name came via engine builder Lanny Trefz, a good friend of Arias’ who was also well acquainted with Bob Denbeste, of Denbeste Motorsports. Denbeste’s passion, beyond having an impressive collection of Shelby automobiles, is building licensed replicas of Carroll Shelby’s classics. Denbeste also acquired Carroll Shelby Engine Company, building and selling classic Ford engines and performance parts, specializing in engines for Shelby applications. The Arias/Shelby package was conceived as a unique high-powered package that would be right at home in one of these exotic vehicles.

The Build

To show off the engine combination’s capabilities, the engine featured here was built to compete in our annual engine building competition, the AMSOIL Engine Masters Challenge. Lanny Trefz’s LTR Engines took on the task of the build. Trefz started with a Shelby alloy 9.5-inch deck Windsor block featuring A356 T6 aluminum construction with beefy billet steel mains and centrifugally cast dry sleeves. This high-end block is built to take punishment, while coming in at a weight of only about 90 pounds. The aluminum alloy block is just the item to provide a tremendous power-to-weight ratio in the Shelby vehicles, shaving over 100 pounds compared to a production block, and substantially more compared to the iron aftermarket blocks typically used in high-powered engine builds.

Naturally, you don’t cut corners when building an engine like this, so Trefz filled the bottom end with some of the best components the aftermarket has to offer, starting with a Scat billet steel crank cut for 1.88-inch Honda journals. Trefz explains: “The small journals reduce rotating mass and inertia, and cut friction through the reduced bearing speed. I was basically building a NASCAR-style bottom end.” The aluminum block will expand more than a comparable iron unit, so special consideration is given to the main bearing clearance. Trefz points out: “As the block grows, so does bearing clearance, so the mains are set up tighter than with an iron block. Working out the details of what is appropriate given the material is all part of the build process.”

Attached to the crank are Carrillo rods and gas-ported Arias pistons specific to the top end combination. Trefz had the pistons cut for very narrow-section .8mm compression rings from Total Seal. As Trefz explains, “The narrow ring actually provides more unit loading on the cylinder wall for a very good compression seal. The gas ports supply pressure to the back of the ring, while the surface area is reduced due to the thinner profile.” The combination worked extremely well, with Trefz reporting negligible leakage past the rings when testing leakdown, and a combustion space that was very clean after running.