Ford FE engines (with the notable exception of the SOHC) use a single shaft-mounted rocker assembly per cylinder head. This shaft is attached to the head with four pedestals and 3/8-16 fasteners. Factory-style rockers, whether original equipment or aftermarket replacements, are steel or ductile iron with either a ball or cup pushrod end and a radiused contact for the valve.
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Factory rockers come in adjustable and non-adjustable designs. The latter is far more common and is used in most OEM hydraulic lifter FE engines. Adjustable-style factory FE rockers have an interference threadadjuster screw on the pushrod end and use a cup-type pushrod, as compared to the ball end used with the non-adjustable rockers. The interference thread is designed to remain in position when adjusted but often loosens in service after many adjustments have been made.
The ratio for adjustable rockers is normally quoted as being 1.76:1, while the non-adjustables are referenced as having a 1.73:1 ratio. The rockers ride directly on the shafts with no bushings. If you see a set with bronze bushings, they have been reconditioned. While bronze is likely a better wear surface than steel alloy, the cross section and strength of the rocker itself has been reduced and it is more prone to break.
Factory rocker assemblies use springs between each rocker to keep them located on the shaft. The end rockers each have a spring washer, flat washer, and cotter pin for retention.
The shaft-mounting pedestals on most FE engines are cast aluminum with a round passage for the shaft to slide through. On certain 427 performance applications, the pedestals are steel with a horizontal split in the shaft passage, allowing the pedestal to clamp onto the shaft. The additional clamping and support is important. The factory shaft setup has a tendency to fracture at the head-mounting hole because the end exhaust rocker is unsupported. The mounting hole on the factory pedestals is often larger or oblong in the section below the shaft to allow more oil to reach the shaft. The pedestals used in high-riser and tunnel-port applications are considerably shorter than the more common parts and cannot be interchanged.
Shafts are gun-drilled steel and have holes for the mounting fasteners as well as for oiling. Oil runs up through the second pedestal on each head, through the center of the shaft, and out the oil holes to the rocker. If there are oil holes on only one side of the shaft, they must face down, toward the cylinders during installation. Factory shafts have holes for cotter pins and cup plugs at each end. The cotter pins serve double duty—retaining the end exhaust rockers, and adding insurance that the cup plugs stay in position.
Upgrades to the Factory System
The original FE rocker system is considered a weak point, and should be upgraded to match the specific high-performance build. Installing adjustable rockers is the most common initial upgrade so the engine is compatible with an aftermarket cam, modified or milled block, or heads.
Replacement or reproduction adjustable rockers are still available from multiple suppliers, and are a simple slide-on replacement for the factory non-adjustable parts. The other change is required for the conversion is the use of different pushrods. Non-adjustable rockers use a common pushrod with a “ball” shape at each end; the adjustable ones use pushrods with an upper cup and lower ball at the lifter end.
Improved versions of the factory adjustable units were available from Crane (now out of business) and Iskendarian. These have flats machined into the rocker body, a longer adjusting screw, and a locknut—as opposed to the problematic interference threads found in factory parts. Aluminum roller tip rockers are a viable option as well, with costs being fairly similar and the advantage of reduced valve guide wear. Horsepower differences are nominal. We recommend upgrading to the aluminum rollers at the 500-hp or 6,500-rpm levels.
Replacing the factory rocker spacer springs with aluminum bushings is an easy and inexpensive upgrade. If you over-rev the engine, the valves can “float” and the pushrods may bounce right out of the cup on the rockers, resulting in considerable damage. Keeping the pieces together with the spacers reduces the amount of carnage in the event of a problem. It’s cheap insurance.
The next upgrade should be in material and end supports for the rocker shafts. The factory setup has four 3/8-inch-clearance holes in each shaft for the mounting fasteners to go through. The end exhaust rocker arm is unsupported, and therefore it’s fairly common for the shaft to fail at the mounting hole under severe use. Heavier-duty shafts, made from better material with a reduced inside diameter, offer some measure of increased durability.
Multiple suppliers offer systems to provide enough end support. These range from a basic set of stands with end support added, to a sophisticated system using the outer/upper head bolts as an added rocker mounting point. The most common and least expensive is a U-shaped pedestal at each end of the assembly, which serves to capture the shaft and reduce flex. These work quite well in milder applications, and are a good option for budget-oriented builds. I’ve frequently run end-stand-equipped standard valvetrain systems at 6,500 rpm as long as open spring pressures are below 600 psi.
Aftermarket Valvetrain Systems
Buying each rocker system part individually costs about as much as buying a complete rocker system. Therefore, buying a complete system is often simpler and more cost effective. Because all the parts are designed to work together, the systems offer better performance and compatibility than separate parts assembled as a complete system. On the good ones, the geometry is right, the spacers and shims (if required) are in the correct positions, and the package has been proven to install and function with a minimum of added effort.
Popular systems follow one of two strategies. They are either an upgraded package that shares the factory-design architecture and features a single shaft with spacers and stands or they are a complete design departure from the factory stuff, with multiple shafts and an adapter mounting plate.
For example, the kits from Dove, Harland Sharp, and Erson follow the first approach. They use the four factory 3/8-inch fasteners to attach the rocker assembly to the heads and require no modification to the cylinder heads for installation. The Erson rocker system is my personal favorite. Erson combined two of the pedestals, an end support, and a spacer into a single aluminum block, simplifying the system considerably while adding rigidity and strength.
In comparison, the system by TD Machine Products uses a mounting plate and four individual shafts, with two rockers per shaft. Five long upper-cylinder-head bolts (included in the kit) fasten the mounting plate to the head for a much more robust assembly than stock. However, if you use the TD setup on a factory or Edelbrock cylinder head, you must machine down the factory-style rocker mountings level with the upper row of head bolts. Note: This renders the heads unusable with any other rocker system—a significant commitment. The T&D rocker system used on Blue Thunder heads is a different story because it uses the additional eight mounting provisions included in the cylinder head—it’s quite possibly the most durable FE package available.
Installation, Alignment and Geometry
The FE is unique because of the pushrod arrangement. Pushrods install through tubes cast or machined into the intake manifold. It is far easier to measure for pushrod length and check for geometry issues before installing the intake because the rocker system still needs to be removed before the intake is mounted.
The key items covered here are: rocker-shaft height relative to the heads, adjuster settings, and rockerarm position on the valve tip—both lateral and in contact pattern.
There are multiple schools of thought on the optimum rocker geometry. One philosophy focuses on minimizing the width of the contact pattern on the valve tip, another concentrates on getting the rocker parallel to the valve at the mid-lift point, and yet another targets maximum possible lift. The TD rocker system provides a gauge to measure the preferred pivot position, but you’ll need to test fit and measure the other systems before making a trial run on geometry. The process of measurement and inspection is equally, if not more, important than the chosen methodology or theory because all methods yield similar results on street or moderate strip use engines.
For this part of the discussion, let’s assume that valve length and spring installed heights have already been pre-determined because it’s a key aspect of the cam selection process. On an FE, the pivot point of the rocker is somewhat “fixed” in comparison to those engines using ball pivot rockers. The only way to change the pivot geometry is to alter shaft height relative to the head or to move the mounting holes, either of which is a major job. The factory-installed spring height is 1.82 inches. If you are increasing this to accommodate larger cam lifts, you need to make a commensurate increase in rocker-shaft stand height with shims or custom stands, so the correct position in the rocker’s arc of travel is maintained.
Minimizing the width of the contact pattern probably produces the best reward on a factory-style rocker system where scrubbing occurs as the rocker travels across the valve tip. Reducing the travel intuitively reduces side loads and improves guide life. But on an FE the valve contact pattern cannot be easily altered, assuming that the shaft pivot height has been corrected as necessary. If the contact pattern is off-center from the valve, try a different set of rockers. A rocker that is too short or too long, as measured from the shaft centerline to the contact tip or roller tip, cannot be compensated for. This problem was evident with the Crane rocker system–where the rocker arms were not dimensionally correct. Unfortunately Crane went out of business before the issue could be addressed.
Given the difficulty of altering the contact pattern on an FE, I consider it something to check. But I put a greater focus on centering the arc of travel and avoiding component interference.
In comparison, side-to-side alignment of the rocker tip relative to the valve can be easily altered on an FE engine. A quick visual inspection will show you whether a problem exists. The rocker tip should be centered on the valve tip when viewed from the side. In most cases, you can make an alignment correction by simply adding and relocating the shims that are alongside the rocker in question.
It is very common to find valvetrain-component interference on these engines. The pushrod upper cups hit the underside of the rockers if the pushrods are too long. In addition, factory rocker arms hit oversize valvespring retainers on the underside of the rocker. Factory rockers can also have the shaft surround come into contact with the pushrods on high-lift cams. And it is very common to have the pushrods hit on their “tubes,” which are cast or drilled through the intake manifold. All these areas need to be carefully checked and any contact eliminated before final assembly.
When installing the traditional FE rocker assembly, be very careful not to excessively bend or distort the shafts. The single-unit structure of the rocker assembly means that, no matter what, you will be compressing some of the valvesprings while putting things together.
Carefully and slowly install components to reduce the possibility of damaging the shafts or the mounting fasteners. Get all four bolts started, then move from one to the other and tighten them about a half turn each time. The idea is to keep the shafts as straight as possible and to minimize excessive loads against any single fastener. Be absolutely certain that the bolts have enough threads to tighten without binding against the head or being too long. Fasteners that are too long bottom out and reach the torque value without clamping the pedestals and breakage results. I highly recommend using studs instead of bolts. It makes installation far easier and virtually eliminates any chance of broken or stripped-out mounting holes in the heads.
Note: If you are using the Erson setup, you must use the smalldiameter AN washers supplied with the rocker kit. Normal washers, including the original factory parts interfere with the rocker arms. Second, if you are using cylinder-head studs, add a clearance notch at the bottom of each Erson end-stand pedestal. Otherwise, the extra threaded portion of the end head studs hits the pedestal.
When mounting a TD setup to common FE heads—original iron or Edelbrock—you first must have made the machining alterations to the head castings as described in the rocker’s instructions. The rocker mounting cradles are then assembled to the heads with the longer head bolts that are included in the rocker kit. Head studs cannot be used with this system. Mounting a TD system to Blue Thunder heads is a straightforward, bolt-on affair using the provided fasteners. It’s important to verify the correct orientation of the shaft recess in its cradle; it is slightly offset with the narrower “ledge” facing the intake side of the head.
Measuring for Pushrod Length
The first part of measurement for pushrod length on an FE requires that you set up the lash adjuster. Try to keep only a few threads exposed below the body of the rocker arm. You should never put a side load against a sharp-edged item, due to the risk of breakage. A rocker with the adjuster turned way down positions the cup far away from its oil supply, and also puts the pushrod through a greater arc of travel relative to the intake manifold, thus increasing the likelihood of interference.
You do not want to get the pushrod too close to the rocker though, especially with the FE-specific cup-style pushrods. A pushrod cup hitting on the rocker body at peak lift will cause eventual valvetrain failure.
All of these things may be sacrificed when necessary to correct for other more critical interference issues, but at least then it is done with knowledge of the risks involved.
With the rockers torqued in place, the adjuster in proper position, and the cam on the lowest point in its profile (the base circle), use an adjustable checking pushrod to determine length. The checking pushrod can either be purchased or made from an old pushrod and some threaded rod. On an FE using cupstyle pushrods, it is important to verify the proper cup diameter is used during measurement. FE engines use a 3/8-inch-diameter cup while many other engines use a 5/16-inchdiameter cup. Even without a cupstyle checker, you can still make an accurate measurement using a ballend checking pushrod by measuring from the bottom of the adjuster ball. When doing this, you need to specify that you are using “bottom of cup” dimensions; the pushrod company will know exactly what you are saying. With all the clearance between the lifter and the rocker adjuster lightly taken up, remove the checking pushrod and measure it with a 12-inch dial caliper.
If you are running a hydraulic cam, add the desired lifter preload to the measured length. If you are running a solid cam, theoretically, you subtract the desired lash. While preload is measured directly at the lifter, lash is measured at the valve; a .020-inch lash is only .011-inch on the pushrod side due to the 1.76:1 rocker ratio. Because valve lash is even less when cold, the dimensional difference is often very small. A common value is .009 inch cold and thus only .005 inch at the pushrod—approaching the point of being insignificant because the adjusters go .040 inch in a single turn.
Checking the Intake Clearance
With the rockers, stands, and proper-length pushrods chosen it is time to test fit the intake. (Intake installation is covered in Chapter 10.)
The FE is unique among V-8 engines with the pushrods running through cast or drilled passages in the intake manifold. With mild valvetrain combinations, there are normally no problems. But as the cam gets larger and the package gets more aggressive, it is really common to have contact between the pushrod and the manifold. Usually this is a “rub” on the carburetor side of the passage due to the increased arc of rocker travel. The use of offset rockers to permit larger, straighter intake ports also creates side-to-side interference potential.
Test fitting the intake and checking with a flashlight and machinist’s dye are the only ways to verify that all interference has been eliminated. It is common to grind on a few passages, and not unusual to find numerous ones needing attention. In addition, it is a fairly common procedure to redrill the openings to accommodate larger-diameter thinwall- tubing inserts for race engines. On an FE, I strongly recommend test fitting the intake and pushrods before “glueing” components together with any kind of sealant. Therefore, multiple test intake installations are the norm rather than the exception on these engines.
Written by Barry Robotnik and Republished with Permission of CarTech Inc
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