There’s no denying that when it comes to the most advanced engine technology, the big name (and big-dollar) racing series are often at the forefront of design and development, since their competitiveness within the rules package often dictates their funding. Several months ago, we brought you Chevrolet’s cutting-edge NASCAR engine being repurposed as a badass street/strip engine. Now, we’re bringing you its bleeding-edge counterpart from the Blue Oval, being repurposed for a top-level off-road race truck team.

Based on Ford’s NASCAR Cup-specific FR9 engine design, Jeff Huneycutt takes us on a tour of what might very well be the most exotic cam-in-block engine on the planet — the Wilkins Motorsports-modified RY45. The RY45 was an engine package that took Roush-Yates‘ knowledge of the FR9 engine in Cup competition and applied the parts to other forms of motorsport in the RY45.

Obviously, the “RY” in the name stands for “Roush-Yates” while the “45” denotes the engine’s 4.500-inch bore spacing. That’s 0.120 inch larger than the standard 4.380-inch bore space of the Windsor family. Designed to be more budget-friendly than the FR9 program for folks not working with huge backing, the FR45 has found its largest market in dirt super late-model racing. However, Sandy Wilkins of Wilkins Motorsports has been putting his spin on the RY45 for other forms of racing. Which makes sense, since Wilkins was part of the original RY45 design and development team.

RY45s for the Dirt

For the Carlson Motorsports team to be competitive in the Pro-4 class in the Amsoil Championship Off-Road Tour, they requested between 890 and 900 horsepower to be competitive. For the 2020 season, Wilkins was able to provide the team with 925 horsepower and is hoping to eke out a few more ponies in this rebuild. As such, Huneycutt points out that some of the engine’s details are being kept close to the vest.

The RY45 engine block is very similar to the FR9 block, in that the casting has undergone extensive Finite Element Analysis-based design to be able to eliminate every last possible ounce from the final piece without requiring hours of additional machining. The 4.500-inch bore spacing allows for a maximum bore of 4.250 inches and the design of the cylinders and main webbing along with the 9.200-inch deck height allows for up to a 4.00-inch stroke. Additionally, the RY45 block has provisions for bolt-in piston squirters to keep everything cool.

The actual bore and stroke of this particular engine weren’t disclosed, simply because it’s not the normal arrangement. However, the total displacement was shared, coming in at 438 cubic inches. The crankshaft is a completely polished, billet-steel knife-edged piece from Bryant. The work of art sits in a set of 2.750-inch coated Clevite H-series main bearings while a set of billet-steel, four-bolt main caps hold the crankshaft in place.

The rods use the same Clevite coated bearings, but because the crankshaft has an enlarged fillet radius at the journal, the bearings are narrowed on the lathe before installation into the Carrillo forged H-beam rods. Their center-to-center length is another of Wilkins’ undisclosed specifications, but the rod bolts receive a massive 100 lb-ft of torque to achieve the desired .0065 inch of fastener stretch.

The pistons are from Mahle, featuring a cutting-edge lightweight boxed design. There is not a surplus gram of weight on these pistons, from narrowed skirts to a narrowed pin boss and shorter wrist pin. The flat-top crowns have a large intake valve relief, and small exhaust valve relief, and sport a .043-inch/.043-inch top and second-ring thickness.

Providing the lubrication for the 8,500rpm engine is a Dailey Engineering dry-sump system. Its four-stage scavenge system draws from individual, sealed-off compartments in the oil pan, and uses no external pressure lines, as all of the fluid is moved through internal passages in the billet aluminum oil pan system. The external pump assembly bolts directly to the pan serving not only as a direct connection for the pumps, but a convenient mounting system as well.

In a very unique configuration, the ATI Super Damper harmonic balancer is placed behind the timing set and is attached to the crankshaft not through a traditional interference fit and center crank hub, but rather by being sandwiched between the lower crank gear and the hub face of the crank snout.

In a very unique arrangement, the balancer is behind the timing gear in order to move the center of gravity rearward.

8,500rpm Valvetrain and Top End

In order to properly seal the cylinder heads to the block, sixteen head studs of various sizes are utilized to generate the required clamping force on the cylinder heads. Cometic MLS gaskets, which have been custom-designed with help from Wilkins, provide the actual seal between the head and block.

The RY45 cylinder heads are a no-compromise aluminum cylinder head design. The 37cc chambers combine with the flat-top pistons to create a near 15.0:1 compression ratio. The tiny chambers house large 2.170-inch titanium intake valves and 1.650-inch titanium exhaust valves, both with a lightweight 7mm valve stem. Intake and exhaust port volumes are confidential, but are quite large and the same as the FR9 Cup engine ports.

In order to not just survive at such high engine speeds, but to thrive in them, the components used have to be extremely well matched. As such, some of the specs — like all of the cam-lobe specs — are kept as proprietary information. However, what was shared is that the camshaft is a billet solid-roller design, with a 60mm base circle. As part of the RY45 block design, the cam tunnel is completely closed off, with only the lifter bores and a single oil feed port having access, meaning the cam and lifters are constantly bathed in oil.

Like the block, the cylinder head’s profile is designed to carry an absolute minimum of weight. The 37cc chambers allow for almost 15:1 compression with the flat-top pistons.

The lifter bores .937-inch in diameter with keyway bushings installed. Jesel solid keyway roller lifters are utilized in order to keep valvetrain mass down, and provide extra pushrod clearance, without link bars. The lifters are coated in a Diamond-Like Carbon coating to increase wear resistance in the lifter bore.

The valvesprings are a dual nested arrangement, with titanium locks and retainers with a 2.165-inch intake installed height and a 2.085-inch installed height on the exhaust. Additionally, the cylinder heads feature integrated valvespring oiling towers, which douse the spring in engine oil to help keep them cool and dampen harmonics.

A shaft rocker system from Jesel with a massive 2.15:1 rocker ratio translates motion from the camshaft to the valves. While the rocker system is available both with and without the adjuster mechanism (to save weight), since the team will be performing maintenance at the track, the team opted for the adjusters.

Since the RY45 was originally intended to be run with a carb and a distributor, and this one will be utilizing port fuel injection, the distributor hole is blocked off and a crank trigger and cam position sensor had to be fitted to feed the Motec M140 ECU the data it needs. A billet single-plane intake manifold is outfitted with the series-specified fuel injectors in the runners, while the 1,000cfm Braswell series-spec throttle body sits atop a four-hole tapered spacer.

The results for all of this work and effort are quite impressive. 958.4 horsepower at 8,500rpm and 657.8 lb-ft of torque at 6,600 rpm, makes for a stout 2.19 horsepower per cube, and a stout 1.50 lb-ft of torque per cube. Additionally, that’s an extra 33 horsepower over last season’s engine, which the team was already incredibly happy with.

Visually, this is a pretty boring dyno graph. But once you read the numbers — 958 horsepower at 8,500rpm and 657 lb-ft of torque at 6,600rpm — the awesomeness really starts to sink in.