Jim Smart
September 15, 2007

Marvin McAfee of Marvin's Custom Engines (MCE Engines) is a dyed-in-the wool engine-building professional. He's outspoken, to be sure, but there's no bull going on here, just hard facts. He's been studying and building internal-combustion engines since before the Korean War.

McAfee cut his teeth learning as much as he could about heat energy at the dawning of the jet age, digesting all he could about gas turbine engines. He has wrenched on everything from first-generation post-war jets to more mainstream Boeing 727s. If you're fond of old warbirds with big radial-piston engines (affectionately known as "round motors"), McAfee's been there, too. He's pulled more than his share of jugs and mag-checked hundreds of magnetos amid the roar of spinning propellers and screaming turbo compressors.

It hasn't always been about flying for McAfee. He has a passion for racing, having rubbed elbows with the likes of Dan Gurney, Carroll Shelby, Jack Roush, Jerry Titus, Parnelli Jones, and a host of other Ford racing legends in SCCA Trans Am competition long ago. At the time, '69-'70 Mustang SportsRoofs were tearing up the asphalt (and Chevrolets) from sea to shining sea. McAfee was crew chief on the independently raced Jefferson Enterprises Boss 302 Mustang 37 years ago. In his chest beats a heart still ready to race at the age of 73.

Are you ready to learn about McAfee's winning strategy? We enjoyed sitting down with him, jawing about the science of internal combustion-the simple physics of how power is made. He will never kid you or bench race with a load of cattle droppings in his pocket. For him, making power is simple physics and nothing more. There's no magic here, he stresses. For an engine to make power, there must be proper building techniques and the right combination of parts that work together in perfect harmony or you're just wasting time and money. McAfee has the unique quality of being able to mentally get inside an engine to see what happens under given circumstances. He applies this talent to his engine building technique, and his discipline never wavers.

The MCE 347 Hammer we're about to build is all about real-world physics- making power and understanding how heat energy becomes mechanical motion. The engines make power from heat energy and how much of it is kept and used. When fuel and air ignite in the combustion chambers, a tremendous amount of heat energy is created with the light off.

This is FRPP's M-6010-B50 Sportsman block right out of the crate. It's a high-strength budget block ($1,050) you can take racing or cruising. Although it's finish-honed, you can take it to 4.030 inches. It weighs just 10 pounds more than your 302 block and is a direct replacement.

So what's heat energy anyway? With fire and the resulting heat comes thermal expansion. When thermal expansion acts on a piston crown, it drives the piston downward in a cylinder bore. Heat energy acts on the connecting rod and crankshaft, turning linear motion into rotary motion.

Did you know most heat energy is lost out the exhaust, into the coolant, and past the piston rings? A huge percentage of the fuel we burn is lost. Only 33 percent or less is actually used to do an engine's work. McAfee believes in keeping as much of that heat energy as possible. The 347 Hammer is a dyno experiment in how to put heat energy to work.

In the months ahead, we'll take MCE's 347 Hammer to the dyno and experiment with different types of cylinder heads and intake manifolds to determine how to make the most of the engine McAfee has built. We may even swap a carburetor or camshaft along the way. But whatever happens, we'll teach you how to make power, and how heads, manifolds, camshafts, and compression ratios alter power output.

See, it isn't always about horsepower, which car magazines and Madison Avenue like to hype. It's also about torque-where the real power is, the grunt that gets us going in the first place. Horsepower gets all the headlines, but torque is what you want most and in the rpm range you use most.

Hammer Down A Foundation
Because we're building an engine that will produce approximately 500 hp, we could have used a factory 302 block. Since we'll be thrashing on this engine at the limits of a 289/302 block's architecture, McAfee wanted a solid foundation on which to build. We're going with Ford Racing Performance Parts' Sportsman block with two-bolt mains. [Recently replaced by FRPP with the more improved Boss 302 casting.-Ed.]

McAfee's disciplined policy about engine building is this: trust, but verify. When {{{Summit}}} Racing shipped MCE Engines this Sportsman block, he gave it a close inspection, then sent it off to Motor Magic in Lake Havasu City, Arizona, for further inspection and machine work. Rare is the block or head casting that doesn't need massaging when it arrives.

Never assume a block or head is ready for assembly right out of the crate. Every FRPP block we have used for engine-building projects in Mustang & Fords has required a certain amount of machine work. The same can be said for preassembled heads. Every block that comes through MCE Engines receives a close inspection and machine work. New blocks are bored 0.030 inch oversize to ensure cylinder trueness. Decks are milled to guarantee a perfect marriage between heads, manifold, and block. The line bore is also checked and honed as necessary. McAfee stresses you should avoid line-boring unless you're absolutely forced to do so because it will adversely alter crank-shaft and camshaft centerline spacing. This will force you to find an undersize timing set. Honing cleans it up and crosshatches the bearing saddles for added security.

All oil-galley passages are massaged smooth to reduce fluid turbulence and increase flow.

Block Prep Pointers
Before McAfee sends the B50 block to Motor Magic, he goes over all the details. Oil galleys and coolant passages are massaged smooth to reduce fluid turbulence. Bolt holes are chased with a thread chaser. Stress risers (ragged edges) are surfaced to prevent cracking.

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