It’s been a decade since Ford introduced the Coyote engine, which was the evolutionary successor to the 4.6 and 5.4L “Modular” motor. Needless to say, the Coyote’s robust architecture and impressive performance has boosted Mustang popularity, and the potent 5.0L mill has also become a popular swap for classic trucks, hot rods and kit cars.
In stock form, the engines have proven to be quite reliable. But given the performance enthusiasts’ penchant to increase power, in many cases the factory fasteners are simply not up to the task. All modern engines are assembled using torque-to-yield (TTY) bolts. They are technically yielded by design, and not intended to handle significant increases in combustion pressure and loads. What’s more, as they are yielded they should NEVER be re-used.
The engineering team at ARP has literally “dissected” the Coyote and rigorously tested every key fastener used to assemble the engine. It should be pointed out that ARP’s sizeable in-house lab contains a plethora of equipment that can evaluate the strength, load capability and fatigue life of any fastener and perform computer-controlled cyclical testing. Subsequently, ARP has developed improved fasteners for all important tasks and listed them all in a handy Coyote Product Guide.
Critical Engine Fasteners
As you would suspect, increasing combustion pressure through power-adders or higher compression pistons dictates replacing the stock TTY (torque-to-yield) head bolts with high strength studs to ensure proper sealing and prevent head gasket failures. ARP’s Coyote replacement head studs are manufactured from the proprietary ARP2000® material that’s nominally rated at 220,000 psi tensile strength. They are available for both M11 and M12 applications.
It should be noted that it’s not simply the fact that ARP uses a superior material, but special manufacturing operations like heat-treating the studs in-house in special racks for balanced penetration and rolling threads after heat-treat that contribute to improved durability —like 10-times better fatigue life.
The Coyote’s bottom-end is easily strengthened through use of ARP’s heat-treated 8740 chrome moly main studs, which are nominally rated at 190,000 psi and far superior to factory TTY bolts. The main cap kit includes four studs –as well as two side bolts– per cap to provide rock-solid support. Parallel-ground flat washers and 12-point nuts are also included.
An often overlooked fastener in builds is the critical bolt that secures the harmonic damper. ARP has developed a special heat-treated 8740 chrome moly bolt with a large 12-point head that makes it easy to rotate the engine by hand to set timing without the fear of rounding the head off as often the case with OEM hex bolts. It comes with a big ¼-inch thick wide area washer to better distribute the clamping force.
Lesser Known Fastener Upgrades
One of the Coyote’s strong suits is its DOHC configuration, and ARP engineers have paid particular attention to developing superior alternatives to factory cam phaser, cam sprocket, and cam tower bolts that help maintain accurate cam timing.
ARP does not list a separate exhaust kit for the Coyote in its catalog. No problem. Use an accessory stud kit (P/N 400-8036) that contains 16 polished stainless steel M10 studs (1.25/1.25 thread pitch) plus 12-point nuts and M10 washers. They are 1.900-inch long and work well with most header flanges, while other length stud (and metric bolt) kits are also available. It is worth noting that ARP employs a proprietary alloy that is nominally rated at 180,000 psi tensile strength —a full 20% stronger than Grade 8 hardware.
These polished stainless steel and similarly rated black oxide finished 8740 chrome moly fasteners are available in a wide range of sizes and lengths (SAE fine and coarse thread from #10-32 x ½-in. to ½-in. x 6 inches) plus Metric M6 to M12 with a choice of 12-point or hex heads. They come in handy 5-packs. Add in a series of “bulk” studs in a variety of sizes and you can secure most anything in the engine compartment.
And when you’ve amped up the Coyote’s power it makes good sense to make sure your driveline benefits from the extra security of ARP’s special 8740 chrome moly flywheel bolts. They feature large diameter (3/4-in. wrenching) 12-point heads that distribute the clamping load better than ordinary bolts and have a larger-than-stock shank diameter for increased strength and improved flywheel register.
The bottom line is that building an engine with premium quality ARP fasteners provides you with increased clamping force over OEM hardware, with an extra margin of safety, and the ability to re-use them (unlike factory TTY bolts). It’s clearly a long-term investment in reliability.