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460 cubic inches is a pretty iconic displacement for the Blue Oval-faithful, as it was the largest factory displacement offered by the 385 big-block Ford engine family. Normally, the 460 gets its displacement from a 4.360-inch bore and a 3.850-inch stroke, with the drawback of being quite large — both in physical size and total weight.
Now, if you could get that displacement, in a significantly smaller, lighter package, that would be an all-around win, right? Prestige Motorsports thinks so, offering just a Windsor-based engine package that comes in right at the 461 cubic-inch mark (just a tad over, actually) with a little room to grow. Jeff Huneycutt of The Horsepower Monster headed down to Prestige’s facility to document the engine’s build.
Oversized Small-Block Short-Block
Obviously, getting 460 cubes out of a small-block Ford isn’t just a “slap-it-together” combination, and the block really is the foundation for such large displacement. So, they started off with a Dart 9.5-deck SHP block, which is an aftermarket version of the Ford 351 Windsor block. A factory block wouldn’t be able to accommodate the bore and stroke needed to reach this project’s displacement goals.
Squeezing 460 cubic-inches into a small-block can be pretty tricky. With the maximum 4.250-inch stroke, you can see how the rod bolt just clears the block (left), and that the piston comes out of the hole about as far as is safe (right).
With a 4.125-inch bore straight out of the crate, the Dart SHP block can handle up to a 4.185-inch bore while still maintaining a .200-inch cylinder wall thickness. Prestige decided to go with a 4.155-inch bore, to allow for some additional wall-thickness both for strength and for room to clean up the cylinders in a future rebuild.
The SHP block is also built to handle a 4.250-inch stroke out of the box, which is critical, since they will need to use all of that stroke to reach their target displacement. A forged 4340-steel crankshaft was used to achieve the maximum stroke possible.
Attached to the crankshaft are a set of forged 4340-steel H-beam rods from LPC. Measuring 6.200 inches long, they allow for a shorter compression height on the piston, which puts the wrist pins into the oil ring, necessitating the use of a support rail. The pistons are forged units from DSS Racing with their popular “X skirt.”
Even with a 22cc reverse dome, the 4.155-inch DSS piston had to have a second intake valve relief cut in order to accommodate the Twisted Wedge’s 15-degree intake valve angle. The 17-degree exhaust valve angle worked with the provided relief.
In order to keep the compression down, the pistons have a deep 22cc reverse dome which both adds volume as well as helps to concentrate the air/fuel into the center of the chamber. Between the small chambers in the cylinder head and the reverse dome, the compression ratio will be 10.65:1 on this combination. The pistons utilize a gas-nitrided top ring, Napier second ring, and 3.0mm oil ring.
A Melling 10833 oil pump is utilized, along with a semi-fabricated Canton road-race baffled oil pan to keep the engine fed with its lifeblood. An Innovator’s West SFI-approved balancer hangs off the end of the crankshaft and keeps everything settled down.
Prestige used a beefy solid roller camshaft from Comp Cams, which measures .394 inch of lobe lift on the intake and .367 inch on the exhaust. Duration at .050 inch numbers come in at 260 degrees on the intake side and 272 degrees on the exhaust, with a 110-degree lobe separation angle. Riding on those lobes are a set of BAM tie-bar solid-roller lifters.
As you can see in the photo on the left, the slight difference in intake and exhaust valve angles is visible. On the right, Jesel's 1.65:1 Shaft-mounted aluminum rockers not only provide additional stability, but the extra ratio also adds a little extra spice to the camshaft.
Big Displacement Means Big Heads
Topping off the combination is a set of Trick Flow Twisted Wedge Race 225 cylinder heads. These heads feature a 15-degree intake and 17-degree exhaust valve angles as opposed to the standard 20-degree inline valves typically found on a standard Windsor cylinder head. The 225cc intake and 100cc exhaust ports are fully CNC-machined for maximum flow right out of the box.
The combustion chambers are also CNC-machined right out of the box, with a total volume of 65cc. They are filled with a 2.08-inch intake and 1.600-inch stainless exhaust valves with a three-angle valve job and have had the exhaust ports raised .500 inches for improved exhaust flow out of the cylinder head. 1/2-inch-diameter ARP head studs hold the heads securely to the deck of the block.
In order to port-match the intake manifold to the huge intake ports, Prestige first laid Prussian blue on the cylinder head and red machinist's dye on the intake and bolted everything down. That resulted in a perfect image of both the size and location of the head's intake ports on the manifold flange. Then after scribing the locations, several hours of careful work with a grinder later resulted in perfectly matched ports.
To control the valves, the spring kit included with the heads is a dual valvespring setup rated at 235 pounds on the seat and 540 pounds of open pressure with a maximum of .720 inch of valve lift, along with lightweight titanium retainers and 10-degree valve locks. A shaft-mount rocker system from Jesel, designed specifically for the Twisted Wedge heads.
The Jesel system uses lightweight aluminum rocker arms with a 1.65:1 rocker ratio (instead of the OE 1.60:1 ratio) for peak lift at the valve of .650 inch on the intake and .605 inch on the exhaust. A set of 5/16-inch, .080 inch wall-thickness pushrods — 8.950 inches long on the intake, 8.900 inches on the exhaust — are used to connect the lifters and rocker arms.
A Holley Dual Sync distributor keeps the spark going where it’s supposed to, while the engine is fed by a set of 45 lb/hr fuel injectors mounted into the Holley billet fuel rails. A March Performance billet front-drive system was also used to spin the water pump, alternator, and power steering pump. And yes, all the accessories were run on the dyno.
While there are nitrous solenoids mounted on the lid, there was no nitrous used in this test. They are leftovers from a previous test. But both based on the CFM capability and the location of the dual-quad throttle bodies, this lid was expected to be the top performer.
To feed air into the combination, a Holley Hi-Ram base was selected and the intake runners port matched to the massive intake ports. The customer specified a forward-facing lid with a 105mm Holley throttle body. But, since Prestige had a dual 4150 lid on hand for the Hi-Ram, which happened to be outfitted with a pair of 1,000cfm throttle bodies, they decided to try that on the dyno first.
After some quick adjustments on the Holley Terminator ECU, the dual throttle body configuration yielded an impressive 642.7 horsepower at 6,500 rpm and 571.4 lb-ft of torque at 5,400, making more than 500 lb-ft between 4,100 rpm and 6,700 rpm. After swapping out the lids and making a few tweaks to the map, the 105mm forward-facing combination was fired up.
Surprising everyone in the dyno cell, the forward-facing combination made more power across the entire RPM range, with peak power of 668.2 horsepower at 6,900 and peak torque of 590.5 lb-ft at 5,200 for a little more than a 25 horsepower and 28 lb-ft gain at the peaks, as well as a much broader powerband. As Huneycutt says, those are impressive numbers for a naturally aspirated small-block on pump gas, with all of its accessories.
As you can see, there were zero losses when switching from the dual four-barrel throttle-body lid to the forward-facing single-105mm throttle-body lid. I think it's safe to say that everyone involved expected the results to be the other way around.
