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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McAfee uses a rifle brush and drill, plus liberal doses of water and solvent under high pressure to get oil galleys clean. He does this with all passages.

Mr. Clean, Mr. Clean, Mr. Clean
Think your block and heads are clean? Guess again. When McAfee gets a block back from Motor Magic, which has already cleaned the block, he goes to work with the detail of Felix Unger of The Odd Couple. He uses a rifle-cleaning kit to clean deep into oil galleys with soap and water. He also uses a high-pressure mix of petroleum-based solvent, soap, and water to get passages hospital clean. His logic is grassroots-even the tiniest iron or steel particle can score a bearing or damage a piston, rendering a new engine useless in short order. McAfee's job as a builder is to ensure engine reliability, covering details most of us miss. Thorough cleaning prevents contaminates from doing engine damage.

Cleaning begins by completely disassembling the block-knocking out all cam bearings, removing freeze and oil galley plugs, and chemically dipping the block. Some machine shops employ a hot-cook process to bake off all the crud, followed by a shot-blast that makes the iron look new again. After that, a shake-out process removes all of the steel shot. A complete water/soap washing should always follow to remove hidden debris.

Power Heads
Because we wanted to establish a power baseline, we decided to begin with CNC-ported 351W heads from PowerHeads. Using 351W heads has been a low-buck 289/302 upgrade for ages. When you're huffing 347 ci through them, 351W heads make even more sense. PowerHeads does a nice CNC-ported head for less than $1,000-which also maintains a stock appearance, if that's important to you. Ports and bowls are CNC-machined, then hand-detailed to a nice finish. New stainless valve guides, valves, and hardened seats are also included. Valve sizing is also increased to 1.94/1.60-inch intake/exhaust. Stock 351W valve sizing is 1.84/1.54-inch intake/exhaust.

Powerheads 351W Flow Figures
ValveLift IntakeCFM ExhaustCFM
0.100 69.5 62.4
0.200 128.0 109.1
0.300 182.0 150.2
0.350 196.8 161.8
0.400 205.7 168.6
0.450 219.5 171.9
0.500 224.9 173.8
0.550 229.0 174.9

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Our Probe 4340-steel stroker crank gets a bath in dishwashing soap along with a gun-cleaning brush to dislodge any contaminates.

Over-The-Top Dynamic Balancing
Automotive Balancing in Southgate, California, does all of McAfee's balance work. Think of MCE Engines and Automotive Balancing as right and left-brained. McAfee and Rocky Bowen work together in order to achieve above-average engine-balancing technique. McAfee likes reciprocating parts within 1 gram or less of each other, which takes time and commitment. Bowen is committed. McAfee is quick to add there's no such thing as "perfect" balance. The best you can do is get it as accurate as possible. For him, that means a reciprocating weight within less than 1 gram, which is darn close considering current balancing technology. Call this splitting hairs, but the result is smooth operation.

A Balance Of Power
Vibration comes another way when static and working compression aren't cohesive. Static compression is what happens when you crank the engine and check compression. Working compression is what happens when you throw in fuel and air, and light it. Heat energy changes compression depending on cylinder and combustion chamber dynamics. To get all eight bores working in unison, each has to have uniform volume above the piston, which is known as compression height and deck height. What happens to the piston and rings at light-off also affects working compression. How well will the rings seat? This is an unknown until you whirl it around and light the mixture.

Automotive Balancing is one of the most committed balance shops we've ever seen in 25 years of automotive journalism. Bowen gets the information he needs from McAfee, then goes to work with precision balancing. Vibration is destructive, and these gentlemen know it. This is why the additional commitment of time is so important. It's also expensive.

How much volume is there above the piston at top dead center? The distance the piston travels from bottom dead center to TDC is live volume. What's left above the piston at TDC is called dead volume. The dead-volume area is called the combustion chamber. Chamber size affects compression. Valve-relief size, no matter how small, affects compression. Even the area above the top compression rings affects compression. Are the valve heads dished or flat? This also affects compression.

Dynamic (working) compression is when an air/fuel mixture (which decreases volume because fuel drop-lets are considered mass) is moved through the chamber. When you ignite the air/fuel mixture, the chamber temperature rises to approximately 2,200 degrees F, depending on humidity, ambient temperature, and atmospheric pressure.

McAfee says all eight cylinders must have identical compression for the power-and load-exerted on the crank to have any chance of being uniform. When you have a loafing cylinder due to compression variations, the engine runs rough and costs power. McAfee begins his compression insurance policy by cc'ing every chamber and piston to get them all spot on.

During assembly, it's important to take things slow and go step by step. Set the crank; then carefully set each of the caps. Each one should be snugged first; then check the endplay, which should be 0.0004-0.0008 inch, with a maximum of 0.0012 inch. If you're going to rev it high, aim for 0.0008 inch. Torque main caps beginning with No. 3, followed by 1, 5, 2, and 4. Torque them in third values, and check crankshaft freedom with each one. You should be able to move the crank by hand at the snout. If it binds and won't turn, bearing clearances are too tight. Once all caps are torqued, check the endplay again.

It's important to note all pistons must be bore-matched, meaning each bore is honed to match the piston. Ring-end gaps must be checked on all eight bores. This is what real blueprinting is-a precision fit of all components.

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Should You Do A Mock-Up?
We learned the mock-up drill from McAfee. A mock-up is designed to make sure everything fits together properly while there's still time to make corrections. Long after machine work and during final assembly isn't the time to discover things don't fit. Do it early in the going before all machine work is completed. A mock-up:

  • Ensures piston skirts clear crank counterweights
  • Verifies piston/connecting rod to camshaft clearance
  • Ascertains rods clear cylinder skirts
  • Makes sure crankshaft counterweights won't hit the oil pump
  • Confirms piston-deck and compression height
  • Determines crankshaft endplay and bearing clearances
  • Confirms piston-to-valve clearances
  • Determines valve-to-valve clearances
  • Confirms valvetrain clearances (pushrod to cylinder head, rocker arm to valvespring retainer, spring coil bind, and more)

Dry Wit
When McAfee starts his day, he checks his inventory for everything, including a good sense of humor. He brings the latter to work with him because things don't always go well in the engine-building business. There are parts that don't fit, parts that don't show up, and times when there are miscommunications with machinists and suppliers. That's when McAfee looks to a can of Dow Corning 321 dry lubricant to reduce daily friction.

All kidding aside, McAfee coats all moving parts (except piston-ring package) with Dow Corning 321 dry lubricant. Dry lubricant is nothing more than a spray-on graphite lubricant designed to protect moving parts during initial startup. Bearings, lifters, rocker arms, camshafts, and other moving parts get a coating of this stuff for one reason-to eliminate any chance of metal-to-metal contact during startup before oil has a chance to flow under pressure. You can find 321 at almost any professional auto parts store or at Dow Corning's Web site (www.dowcorning.com).

Smooth Fit
Whenever you build an engine, it's important to understand proper fit.The first rule of fitment: If you have to force it, something's wrong. Never beat something to death with a hammer to make it fit. If a cam gear won't slide on the crank or cam, the fit is incorrect. If a distributor gear wobbles on the shaft, it's too loose and unacceptable for use. If any part exhibits sloppy fit, it's not suitable.

McAfee University teaches us that fit is pretty fundamental. Cam sprockets should slide on and off cranks and cams without wobble. If you have to beat them, the fit is too tight. Dress the crank and clean up the snout; then check fit. Ditto for a stubborn camshaft drive gear. There's one exception to this rule: The crank damper must be an interference fit (pinch fit: 0.0005-0.0008 inch). Other items, such as cylinder-head dowel pins, rod caps, main caps, timing cover, and the like should also exhibit smooth fit. When-ever you force something, you're creating unnecessary stress and the potential for failure.

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Oil-Pump Blueprinting
Never install an oil pump right out of the box. Instead, blueprint and sleep easier. McAfee has a routine he follows, and you're free to follow all or some of it. Whatever you do, verify the condition. Check rotor side clearances, properly index the rotors, and check the relief valve for proper operation. Or order yours from MCE Engines for a precision blueprint.

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Stop Leak!
Never has there been a better solution to driveway oil spots than the one-piece rear main seal Ford began using in the early '80s. Did you know you can retrofit an older two-piece-seal small-block Ford with a one-piece? Talk with your machine shop about it. All you need is a boring bar and a smart machinist with a nose for Ford part numbers. The savvy machinist uses the boring bar to remove the seal grooves. With the grooves removed, there's room for the one-piece seal.

One-piece seals are not foolproof, however. To be leakproof, they need a thin film of high-temp RTV (gray) around the circumference, then a spot of RTV on each side of the No. 5 main cap mating surfaces, as shown here.

Effective Communication
For a successful engine build, there must be concise communication between everyone concerned. When McAfee sends his machine work off to Motor Magic, he attaches a tag with detailed information specifiying what's to be done, right down to dimensions and tolerances. Include a tag with your castings, be sure to get it all in writing on the work order, and keep a copy.

Why Blueprint?
If you haven't figured it out already, McAfee is obsessive about blueprinting. Why? Because true blueprinting leaves nothing left to chance. It closely inspects and treats everything to ensure uniformity and proper function. Blueprinting means never losing sleep wondering if you missed anything. So what is blueprinting?

  • Close inspection of every part, right down to fasteners and bolt holes
  • Doing an engine mock-up-preassembly of all parts prior to machine work to ensure proper clearances and fit. No one wants to learn during final assembly that something crucial doesn't fit.
  • Getting compression height and deck height uniform across all bores
  • CC'ing piston crowns and combustion chambers to ascertain volumes; then, making the necessary corrections to get all of them uniform
  • Pinpoint machine work that includes uniform
  • machining of both decks and block ends for proper head and manifold fitment
  • Boring and match-honing all eight bores for precision piston fit
  • Uniform piston-ring end gap
  • Thermal-coat piston crowns for heat protection
  • Low-friction piston-skirt coating
  • Micropolish crankshaft journals and radiuses
  • Chamfer crankshaf-journal oil holes for improved lubrication
  • Relieve all stress risers (imperfections and parting lines) in all castings and forgings to prevent cracking and failure
  • Remove all rough edges
  • Dynamic balancing right down to less than 1-gram weight difference
  • Conversion of two-piece rear main seal to one-piece
  • Use of a one-piece oil pan gasket
  • Coating all moving parts (except piston ring package) with Dow Corning 321 dry lubricant for friction-free startup
  • Use of a roller camshaft and full roller rocker arms for reduced friction
  • One-piece pushrods for durability
  • Precision adjustment of pushrod guide plates for minimal contact
  • Deburr and chase all threaded parts
  • Chase threads in all bolt holes
  • Bevel all oil-galley passages to prevent fluid turbulence
  • Open up oil-galley passages at main bearing saddles
  • Install oil restrictor plugs between main and cam bearings at all journals except No. 1
  • Drill a 0.020-inch oil hole in the passenger-side oil-galley plug for timing-chain spray lubrication
  • Dress crankshaft and camshaft mating surfaces for smooth sprocket fit
  • Micro-hone all lifter bores
  • Port-match intake manifold and cylinder-head ports
  • Precise installed valvespring height
  • Check for valvespring coil bind at maximum lift: 0.050-inch minimum clearance
  • Lap all valves and seats to ascertain full contact

Cylinder Heads
Blueprinting isn't just a bottom-end dynamic. It applies to every aspect of an engine build from top to bottom. What's more, no matter why you're building an engine, including a oncours-original restoration, blue-printing is good common sense. McAfee's blueprinting regiment includes taking the ragged edges off everything, even valvesprings. Each valvespring is massaged to remove rough edges that cause internal friction and power loss. Internal friction is one of the leading causes of excessive heat and power loss. Each source of friction, no matter how small, makes heat and robs power. Add up these sources and the losses mount.

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Cam Selection Help From Comp Cams
Did you know cam selection is easier than ever with Cam Quest 6 software from Comp Cams? Cam Quest 6 is the fastest path to power because it's never further away than your computer. It enables you to dial in both horsepower and torque, as well as when each happens. For more informa- tion, visit www.compcams.com.