From 1991 to 1995, one basic nodular iron crankshaft was produced for Romeo 4.6 SOHC engines--numbered F1AE. It is a five-main-bearing crank with narrow, knife-edged counterweights. During the same period, there was a steel-forged F2LE-AG crank conceived for the 32-valve DOHC 4.6 Cobra engines. This crank is not designed for the SOHC engine, so don't even go there if you're building a SOHC. Beginning in 1996, a new crank was used in the 4.6 SOHC Romeo engines: the F65E steel crank.
When the Windsor engine plant came on line in 1996, it produced its own array of crankshafts, primarily for trucks. This is also an F65E steel crank designed for the Windsor block. Where this gets confusing is the crankshaft flange. Some were six-bolt and others were eight-bolt. Rule of thumb: most Windsor F65E steel cranks have eight bolt holes, only some have been spotted with six.
Like the 4.6 SOHC engine, the DOHC engine is fitted with a lightweight, knife-blade counterweight crankshaft with wide main journals and smaller rod journals. Architecturally, it is virtually the same as the SOHC. The Lincoln 4.6 DOHC engines were factory-fitted with nodular iron crankshafts that could spin happily to 6,500 rpm. Mustang Cobras got the steel crankshaft for greater durability in a high-performance application. The steel crank is configured differently, with additional counterweights at the No. 3 main journal. The steel crank has eight flywheel bolt holes instead of the six we generally see in the SOHC.
The 5.4 started out in 1996-'97 with a forged steel crankshaft for truck use. This pattern continued until 1999, when Ford went to a nodular iron crank in the 5.4 SOHC. The nodular iron crankshafts in both the 4.6 and 5.4 SOHC engines can take up to 500 hp. If your goal is higher, plan on a steel crank.
Here's the powdered-metal...
Here's the powdered-metal connecting rod from a DOHC engine. Note its long, lean design with a cracked cap. Powdered-metal rods are cheaper to make and weigh less than their forged ancestors. These rods are good for up to 400 hp. We suggest aftermarket rods for anything higher.
What makes the 4.6 SOHC rod different than those we find in the older pushrod V-8s is its powdered-metal design with cracked caps. Powdered metal is formed in a mold, then the rod is scored, and the rod end separated (cracked). The cracked cap design makes each connecting rod as unique as a fingerprint. The 4.6 SOHC rod is also longer and leaner than we are used to with older Ford powerplants. Rod bearings are smaller and wider for better load distribution. Romeo rods differ from Windsor rods because they employ pressed-in pins. Windsor rods are all full-floating pins. Powdered-metal connecting rods work quite well in street applications, but they get shaky when we start hammering on them with nitrous or supercharging.
The 4.6 DOHC is fitted with the same powdered-metal connecting rods we find in the SOHC. The one exception to this rule is the '03-'04 SVT Mustang Cobra that has Manley forged steel rods for use in this factory supercharged application. If you're going to really spin your 4.6 or 5.4 engine, powdered-metal rods are a bad idea above 400 hp. if you plan on racing, aftermarket forged steel I-beam and H-beams rods are available for the Modular V-8s.
Word in the industry is, there were three basic pistons used in the SOHC engines from 1991 to 1999: one type for the Romeo SOHCs and two in the Windsors. The Romeo piston is a press-fit-type hypereutectic with a dished crown. Because Ford was aiming for reduced friction, the rings aren't what we're used to with the older Ford engines. The rings are much thinner at 1.5 mm (both compression rings) and 3.0 mm (oil ring pack). Because the Windsor rods sport floating pins, they are bushed and call for a different hypereutectic piston than we find in the Romeo SOHC engines. Windsor pistons, like Windsor engines, came along first in 1996 and remained the same until 1999.
This is a SOHC piston with...
This is a SOHC piston with narrow ring grooves for reduced internal friction. Note the absence of a piston skirt with these guys, again for reduced friction and weight. They are dished to control compression at just under 10:1. DOHC pistons are domed for the four-valve chambers.
Beginning in 1999, Ford fitted the 4.6 SOHC with a better cylinder head called the Power Improved (PI) heads. With those PI heads came a new piston with a deeper dish to allow for a smaller heart-shaped chamber size. Another dynamic common with 4.6 and 5.4 engines is coated piston skirts for reduced friction at the thrust faces. Ford opted for hypereutectic pistons in order to run tighter piston-to-cylinder wall clearances. Running tighter clearances reduces emissions. It also enables these engines to make more power through better cylinder sealing.
The 4.6 and 5.4 DOHC engines run domed forged pistons for increased compression in the four-valve chamber. Ford opted for forged pistons to withstand the pressure extremes associated with this high-performance engine. Like the hypereutectic pistons in the SOHC, these pistons also employ Teflon-coated skirts for reduced friction and heat protection. The ring package is virtually the same.
The '99-'03 Ford Lightning 5.4 SOHC supercharged V-8s were fitted with forged pistons for obvious reasons--supercharging. Higher cylinder pressures make forged pistons mandatory.
The aftermarket offers enthusiasts a wealth of piston types for the Modular V-8s. Manley, for example, offers us forged pistons for the SOHC in .020- and .030-inch oversizes. Federal-Mogul has them in .010-, .020-, .030-, and .040-inch oversize hypereutectic and forged.
This is a primer to get you acquainted with Ford's SOHC and DOHC Modular V-8s. We're going to touch on these engines more in the months ahead, showing you how to make the most of Ford's new-generation overhead cam V-8 engines. We're hopefully going to build them, and we'll look into swapping them into a vintage Ford. Shortly, we will introduce you to Ford's new three-valve Modular V-8 in the new Mustang GT, F-150, and Expedition.