Jim Smart
November 30, 2010
Photos By: Benton Jackson

In every engine builder's life, there comes a moment when it's time to prove something to themselves and to others. This is one such moment for veteran engine builder Marvin McAfee. He's out to prove how much power can be made with the 385-series Ford big-block, while dialing in an appropriate amount of durability.

McAfee has been building engines for more than 50 years. He's an FAA-certified airframe and powerplant technician with abundant gas turbine and radial piston engine experience. He was also a crew chief in SCCA/Trans-Am competition, competing against great racing legends we're all familiar with-Parnelli Jones, George Follmer, Jerry Titus, Carroll Shelby, Dan Gurney, and a host of other history-making notables.

When McAfee began planning to build this 598ci Ford big-block, he intended to go with a stock 460 truck block with standard bores, or perhaps the Ford Racing Super Cobra Jet block. However, he wouldn't have been able to pump 598 ci into a stock block. At the time, we knew that a new 385-series competition block was coming from Ford Racing Performance Parts, and when Ford Racing called us with exciting information about the new competition M-6010-A460 block, McAfee suggested they have Yellow drop one off at his Los Angeles shop.

While the 385-series 460 was factory rated at 365 hp, it could only be opened up so much with regard to displacement. With the M-6010-A460 block, McAfee would be able to take out the bore to a whopping 4.600-inches, and the stroke could be lengthened to 4.500-inches. The A460 block yields an 18-bolt deck on each side instead of the normal factory 10-bolt decks. This means different head, intake, and exhaust gaskets because this isn't an ordinary 385-series engine. The new A460 utilizes a 10.322-inch deck height (plus or minus 0.005-inch), and has a suggested retail price of $2,295.

To keep costs down, McAfee planned to use off the shelf parts that would enable him to break through the traditional horsepower ceiling, along with appropriate spine decalcifying torque numbers. He set a target of 800 hp and 700 lb-ft of torque. To achieve these goals, McAfee expected the powerband to span 2,500 rpm, with a redline of no more than 7,000 rpm.

McAfee looked to Eagle Specialty Products and Mahle Pistons for the enormous displacement he wanted for the T-Rex project. The decision to go with Eagle and Mahle came after consulting with a number of stroker kit manufacturers to determine the best pick. McAfee examined the numbers, electing to go with an Eagle 4340 steel crankshaft that uses 3-inch mains and 2.20-inch rod journals.

The connecting rods are 4340 forged H-beam pieces that measure 6.80 inches from center to center (PN CRS68003D2000). Mahle's best forged pistons were chosen, which started life as a big-block Chevy design with a wristpin location adjustment to make them work with the 460 Ford. This makes them off the shelf pieces you can easily get by filling out an order sheet (PN 99-8402-1). This is the first time Mahle has ever made this particular piston for a 385-series Ford big-block.

When we started talking with McAfee about this project back in 2005, his goal was maximum torque rather than horsepower. Thus he ordered a specific mechanical roller camshaft. As time passed and we waited for the A460 block, McAfee started thinking about why horsepower was more important to this project than torque. Torque is a byproduct to an engine this size. Torque is there no matter what you do with horsepower. With that, he had a change of heart with camshaft selection, opting instead for a different mechanical roller camshaft from Comp Cams (PN 34-850-9).

The bumpstick features an optimum rpm range of 4,400 to 7,200 rpm, and uses 112-degree lobe centers. Valve lift checks in at 0.727-inch for both the intake and exhaust valves, and the duration measures 275/281 degrees at 0.050-inch.

With these specifications, peak torque should happen somewhere around 5,000 rpm, handing off to peak horsepower around 6,500 rpm. While retaining the same lobe centers (112), Marvin has chosen to increase both lift and duration to maximize breathing efficiency at high rpm. It is important to remember horsepower is a product of not only torque, but also rpm. When we increase lift and duration, we enable the engine to ingest a bigger intake charge at high rpm.

McAfee considered stud-mounted rocker arms and guideplates in the original build plan, but after talking with the techs at Jesel Valvetrain, he ordered a complete shaft-mounted rocker arm system. Jesel came up with its best top-of-the-line Mohawk Beam Pro Series shaft assembly (PN KPS-11057). At 195 grams each, this is Jesel's stiffest, lightest rocker arm with the lowest moment of inertia while producing precise valve control with minimum frictional losses.

So these are the basics that will provide the foundation for this 800-plus-hp monster mash engine build. Next month, we'll bring you the induction system and assembly, which will be followed by a third and final installment where we flog it on the dyno for all it's worth.