Photos by Moore Good Ink
McKeown Motorsports Custom Tailors the Induction Systems on These Beauties Like a Fine Suit
The world’s first aftermarket Cleveland crate engine was unveiled recently by McKeown Motorsport & Engineering (MME). They call it the 2K.
Though MME’s 2K crate engine distinguishes itself from its mighty predecessor of the ‘70s and ‘80s in many ways—internally balanced forged crankshaft, deck plate bored and honed, priority mains wet or dry sump lubrication systems and so on—it is the multiple choices of induction systems that set it apart from the conventional crate engine. MME offers five different cylinder heads, and the technicians at the company require specific information to select the correct cylinder heads and induction system for every engine.
The most important element in building a high performance engine—an engine that accelerates quickly—is to know the crucial rpm range in which it will operate. It’s also helpful to understand that high average power output always prevails over peak power, at least in a muscle car, if not a dynamometer.
In addition to stating the engine’s operating range, which influences the runner lengths of the induction system, MME needs to know the car’s weight. The induction system of a 2K engine powering a 2,000-pound Cobra is obviously different from that of a 3,800-pound vehicle. Gearing also has an effect on induction choice. For example, a 2K engine powering a gear ratio of 3.25:1, used to propel the car at 1,500 rpm on the street, dictates a different cam and induction system from that of one featuring 4.11:1 gearing operating at 3,000 rpm. Hood clearance is a further consideration, although the 2K’s 9.2-inch deck height usually provides adequate top and side margins, especially convenient for header fabrication.
Finally, before selecting the right cylinder heads and induction system, MME ponders two further factors. The first relates to the engine’s cubic inch displacement, paying particular attention to bore size and inlet valve size. These components often dictate how the chamber and bowl (the area adjacent to the valve seat) are shaped.
The second factor is the cross-sectional area of the induction tracts, together with valve size and valve angle, as well as port volume and port shape. These elements regulate port velocity. Port velocities, which are measured in feet per second on a flow bench, are affected by low and high pressures within the intake tracts. Low pressure cycles occur the moment the inlet valve cracks open, revealing a falling piston within the cylinder bore. “Without optimal velocity,” says airflow specialist Keith Wilson, “you cannot successfully fill the cylinder—your volumetric efficiency will be inadequate. Moreover, optimal velocity is imperative for maintaining the weight of the fuel while in suspension, as it’s heavier than air. If the fuel loses its fine particle properties and becomes ‘wet’ it cannot recover, and most of it will exit the tailpipe unburned. Without optimum velocity, fuel falls from suspension and power is lost.”
Beyond induction issues, the 2K has benefitted significantly from rapid advances in engine technology. For example, the advantages of modern electronics, both ignition timing management and fuel injection management, as well as CNC-machining, particularly in the forming of asymmetrical camshaft lobes, have had a profound influence on its personality. “But, even in its original form, I’ve always had great affection for the Cleveland,” intimated MME’s principal Mark McKeown, “I admired the efficiency of its cylinder heads, its combustion chambers, its 9-degree valve angle—the Cleveland had few vices. And even though I’ve been developing these engines for almost 30 years, I still get a thrill from working on them.”
Though engine displacements of 408 and 410-ci have traditionally been the MME staple, bigger 427 and 430-ci-plus displacements are now becoming available. Predictably, the power output most commonly chosen for street and street-strip use is between 450 and 750 hp.
With many different qualities to recommend the 2K, here are some of the essential stages captured during a typical pre-assembly process.
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- A broad power band is the essence of the 2K. Exploiting the dominant qualities of different cylinder heads enables it to succeed by taking vehicle weight, gearing, transmission type, low-end torque or high revving horsepower into consideration.
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- Carbide-tipped tooling is used to machine each 2K crankshaft, converting the engine from externally to internally balanced. To reduce crankcase windage, counterweights are profiled and balance holes are plugged and polished.
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- Each of these hand-built engines is supplied with a build sheet, disclosing all internal dimensions, including calculated oil clearances.
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- Every bearing shell is measured and recorded to ensure proper clearance.
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- With strong double rib bearing caps on forged alloy steel H-beam connecting rods, MME accompanies them with forged aluminum custom pistons, Pro Series bearings and rings, and an 8620 nickel chrome-moly camshaft.
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- Each bearing journal is measured and recorded. The 2K runs a forged 4340 alloy steel crank with a 4-inch stroke and 2.750-inch-diameter main journals and 2.100-inch crank pins.
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- Using an inside micrometer, the journal diameter and the bearing shell thickness is subtracted from the respective bore diameter of each connecting rod to reveal the oil clearance.
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- Piston ring end gaps are dictated not only by cylinder bore diameter but also by induction type: naturally aspirated, nitrous oxide, supercharged, or turbo—all require different end gaps.
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- Equipped with priority mains lubrication and offered with wet or dry sump oiling systems, each 2K engine is deck plate bored and honed. Compared with the Windsor, the 2K’s shorter 9.200-inch deck height is an easier fit within the confines of the average engine bay, alleviating the task of header fabrication.
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- Compression ratios can be altered slightly by using multi-layer steel head gaskets, which are available in thicknesses of .027-inch to around .050-inch.
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- The two popular displacements of the 2K engines are 408 and 427 ci. Its 4-inch stroke increases piston speed and improves drivability.
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- Shaft-mounted rockers are infinitely superior to their stud-mounted counterparts. Under high loads they maintain rocker stability, operate reliably at the center of the valve stem, reduce wear on the valve guides, and are less affected by valve train harmonics.
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- A temporary copper shim is placed under the rocker stand to determine its correct height. Once established, a full-size solid metal shim is fitted. Second, the push rod length is determined by using an adjustable pushrod checker. Finally, piston-to-valve clearance is ascertained by rotating the engine with modeling clay placed on top of the piston, removing the head, slicing the clay and measuring its thickness.
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- For those who desire optimum airflow and have no under-hood clearance issues, the powerful CHI heads with high-rise intake arrangement are always strong contenders.
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- Two solid roller race camshafts feature two journal sizes, operating on needle roller bearings. Note the different layout of the valve lobes. For smoother operation MME fires the outer cylinders then the inner cylinders instead of the original firing order, 13726548.
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- High performance 2K street engines are supplied with hydraulic roller tappets, which are maintenance-free. 2K race motors exceeding 6,500 rpm use solid rollers. All roller lifters are of tie bar style and are used in conjunction with standard-base circle camshafts.
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- MME focuses on the complete performance package, analyzing other components that contribute to the engine’s performance. Incorrect fuel pressure or a poor choice of converter, for example, will compromise the calibration of the entire engine.
Tags: McKeown Motorsport & Engineering (MME)
