Ford Coyote Engines. Jim Smart
alt="Ford learned a lot about ...."/>
Ford learned a lot about durability with the Modular engines. It found you don’t always need a forged piston; a well-thought-out hypereutectic piston works just as well. Hypereutectic offers strength without the challenges of forged. Forged pistons yield greater expansion properties and can be noisy when cold.
The Coyote engine shares the same connecting rod dimensions with the 4.6L engine at 5.933 inches center to center; yet it is not the same rod. It is a stronger rod with 12-point bolt heads. Rod ratio is 1.62:1 for excellent dwell time at each end of the bore. The Coyote’s 5.933-inch cracked rod is a sintered metal I-beam piece engineered for extreme street and weekend race duty. However, it is not a rod that stands up to the severe punishment of supercharging and nitrous. If you’re planning a supercharger or nitrous induction, Manley H-beam rods are mandatory over the stock 5.933-inch rod. The stock rod takes a lot of punishment. However, you’re pushing your luck if you use anything less than a heavy-duty forged-steel I-beam or H-beam rod if you plan to push it above 600 hp.
The Coyote piston, shown from another angle, demonstrates how different this slug is from those in the 4.6L/5.4L Modular. It is a lighter piston sporting a protective coating, enabling it to survive higher-combustion temperatures.
The Coyote is fitted with lightweight hypereutectic pistons with coated skirts for reduced friction and wear. Ford engineers weighed the benefits of forged versus hypereutectic and hypereutectic won for its weight and expansion properties. Forged pistons are noisy when they are cold due to excessive piston to cylinder wall clearances, which generate plenty of complaints with 4.6L and 5.4L engines. Hypereutectic pistons run quieter because you can run tighter tolerances without noise when they are cold. The Coyote piston tolerates the extremes of street and weekend race duty and offers durability. However, if you intend to supercharge or use nitrous you’re better off with a forged and coated piston for best results.
Another reason Ford opted for a hypereutectic piston is the oil cooling jets that keep the pistons cooler, which improves piston life. This approach also allows for faster warm up because oil is in direct contact with one of the hottest parts of the engine right from the start. Ford engineers proved that the crankshaft runs roughly 25 degrees F cooler with the oil jets, which enables this engine to operate on 87-octane fuel and survive (although 91-octane is optimum).
Coyote four-valve cylinder heads are left and right specific as well as being a fresh design from Ford. These DOHC heads are downsized for a more compact Modular design with less restriction and improved flow. Cam journal support is more “Windsor” in nature: void of girdles with the simplicity of standalone cam journals. This is a CNC-ported 2011–2014 cylinder head. The stock ports are roughcast.
Most important to remember is clearance issues. Heavy-duty I-beam and H-beam connecting rods don’t always clear the tight confines of the Coyote block. You must first do a mock-up and make sure everything clears by at least .060 to .100 inch throughout 360 degrees of crank rotation with all rods and pistons (without rings) installed. Pay close attention to piston skirt to crank counterweight clearances, which can become very tight and prohibit the Coyote from accepting any more than a 3.649-inch (92.5-mm) stroke. Another area of consideration should be connecting rod interference issues with the piston cooling jets, which has happened in some builds.
Ford’s Ti-VCT Coyote has a new cylinder head design that makes the engine less bulky while providing extraordinary high-RPM breathing. The Ti-VCT’s intake ports are free from restrictive tendencies, outflowing even some of the most legendary racing cylinder heads in the industry. Intake flow numbers are in excess of 300 cfm. Because the Coyote’s top end was designed more as a package than just individual heads, cams, and induction, it produces numbers never seen before in a factory Mustang engine. These heads flow very well without specialized port work, which leaves the door wide open for even more power if you decide to do port work.
The Coyote head is clearly different from the 4.6L/5.4L 4V and is not interchangeable. In front are provisions for the chain tensioner and Ti-VCT feature, which are oil-pressure controlled. As you can see, the cam journals are generously lubricated and the oil galleys are easily accessed. It also has a water jacket freeze plug.
With the left-hand cylinder head in place, identified with an “L,” it’s challenging to see where the head ends and the block begins. The Coyote is a well-thought-out package, where block and head become one. The objective was to come up with a lighter, smaller cylinder head to get unnecessary weight out of the Mustang while conceiving a more swappable engine that can fit more applications. This is how you design and produce a factory high-performance engine.
This is the right-hand (passenger) head, with an “R” (for “right”) and the Ford casting number. At least four cylinder-head castings are available at press time: 2011–2014 standard head, 2012–2013 BOSS 302, 2015–2016 CMCV, and the GT350 head.
Closer inspection shows the great advances of the Coyote’s valvetrain system. The valve angle has been modified for improved flow, and valvesprings and retainers are smaller and lighter. In fact, you may opt for lightweight springs and titanium retainers for even greater freedom. The oil drainback is greatly improved.
The Coyote’s 57-cc four-valve hemispherical chambers demonstrate how different these heads are from previous Modular castings. Four valves per cylinder were surely a given with a performance engine such as this. However, in order to move the intake ports away from the crankshaft centerline and decrease cylinder head width, the valve angle and distance between valves were revised significantly. This revised geometry allows for more valve lift without the risk of valve to piston contact. The intake valves are 1.460 inches in size; exhaust valves are 1.220 inches. The spark plug firing tip is in the middle of the chamber.
Ford’s Ti-VCT design team, specifically Todd Brewer and John Reigger, understood it would have to spend a lot of time to come up with a cylinder head that could do everything. First, they had to perform basic hotrodding tricks to achieve greater flow; then, these seasoned engineers had to jump into areas that they had never ventured into before. Although the Coyote cylinder head appears to be a derivative of the GT500 head, it isn’t. A lot was learned from the GT500 head, yet none of it was carried over.
Engineers had to focus on aspects of port design that had never been considered, such as the distance between the four valves, valve angle, valveseat revisions, and more. Valve angle had to change to improve valve to piston clearances and air flow. Thanks to advanced computer technology, engineers were able to come up with a new cylinder head quickly. It took extensive development work for six months at seven days a week to create a new, more innovative head.
When Team Coyote was finished with basic cylinder head casting development, it had to go back and look at cam profile along with valvetrain size and weight. Think of high-revving motorcycle engines; this is what Ford was faced with in developing the Coyote. Rocker arms and valvesprings had to be much smaller to improve both