Camshaft selection for the FE engine is similar to other cam-inblock pushrod engines. You need to decide exactly what you intend to do with the engine, what you are expecting out of it, what vehicle you are installing it in, and then have a “heart-to-heart” talk with your checkbook.
Among the crowd at the average car show or race track, cams are a topic of considerable debate and often the supposed experts have very little hard data to support their various claims. Reasons for this are numerous, but among professional builders and racers, a cam-andengine package that really performs better than the competition is a competitive advantage, and therefore it is a closely guarded secret. The enthusiast who only builds an engine every few years simply does not have the resources to make comparative tests, in which everything else is held equal, and won’t have the same level of knowledge as a professional engine builder.
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The main thing to learn from the following discussion is this: If the basic selection is reasonably close to the ideal cam specs, the differences between the cams in the plethora of appropriate choices will be modest. Hence, there is no “right or wrong” cam for a given application. Therefore, within a rational range, one cam will deliver one performance characteristic better than another, but on the flip side of the coin, certain other characteristics are not as good as with other camshafts. In other words, one camshaft can’t be everything to every engine. You need to decide which characteristic is most important to you before you choose. To help you make that choice, guidelines for selecting a camshaft are provided later in this chapter.
Camshaft selection is more about context within the build than about any one set of parameters. The combination of parts defines the outcome— not any single item. Getting the absolute right set of cam specs is critical in a race engine, but much less so in a street car because driving behavior is more important than finding the last 10 hp. Don’t become fixated on a particular specification or dimension. There is a reason that professional race teams have dozens of cams in stock; even with all their resources, they still need to try them out to find that elusive “perfect” part.
FE Camshaft Design Specifics
The Ford FE engine does have a few unique design features that need to be considered when selecting a camshaft. Most of these are well addressed by the various camshaft manufacturers and need only a cursory inspection when preparing to install your chosen piece. But they do need to be checked.
The FE uses a single dowel pin in the front of the cam as a locator and drive item. This pin has to be a snug-type (not press) fit, and it should lightly bottom out in the drilled hole in the cam. The original Ford assembly had the pin press fit into the timing sprocket, but the aftermarket timing sets have long since abandoned that practice. On one-piece fuel-pump eccentrics, the pin must be long enough to extend through the timing sprocket and come flush to the face of the eccentric. On two-piece pump eccentrics, a small tab extends rearward into the sprocket, and the pin must be recessed enough from the sprocket’s face to accommodate the tab.
You sometimes need to make a small spacer to slip in behind the pin when it’s not long enough. Other times you end up shortening the pin. This needs to be measured and corrected before installing the pin into the cam because it can be a real challenge to remove without damaging it.
The front cam bolt hole on an FE is a 7/16-14 thread from Ford. Most aftermarket cams are the same, but I have found some with a 7/16-20 fine thread tapping instead. The difference in thread pitch can damage threads if left unchecked. And I often find that the tapped hole is rough and full of debris. It seems that the production cleaning process misses that area regularly. The washer behind that cam bolt head needs to be very thick and strong. Hardware-store-quality parts do not work. On one-piece fuel pump eccentric assemblies, the washer must be large enough in diameter to overlap and retain the dowel pin. If you are running without a fuel pump eccentric, the washer bridges the opening in the sprocket and a thin washer bends and deforms.
The FE camshaft has all five bearing journals at the same nominal 2.124-inch shaft diameter. The number-2 and -4 journals need a groove in their centers for a 427 sideoiler block. These grooves route oil from the valvetrain transfers through to the deck. Enlarging that groove flows more oil to the heads, but that is rarely necessary. The grooves are not required with the common blocks such as a 390 or 428. Those blocks have annular grooves already machined into the bores where the cam bearings are pressed.
The distributor and oil-pump drive gear is behind the front journal. I invest some time checking the teeth for burrs and rough edges. A few minutes spent with a wire wheel, a small file and a knife sharpening stone help ensure longer gear life, especially useful when running a bronze gear on a roller cam application.
The front face of the cam runs against the thrust plate. The cam sprocket slips onto the small snout that extends out from the front. Both of these surfaces need to be clean, flat, and free of any burrs or raised spots.
Cam Thrust Plate and End Play
A cast-iron thrust plate that is surface ground on both sides retains the FE camshaft. A pair of 7/16-14 fasteners secures this plate to the block. On original engines, these fasteners are Phillips-head or a button-head, hex-drive-type screws. A normal hex-head fastener usually clears the aftermarket double-roller timing sets, but you should check to be certain.
The thrust plate, sandwiched between the cam sprocket and the camshaft, allows about .005 inch in cam end play, which should be measured and verified. The plate can be polished to gain some clearance or the sprocket altered to reduce it. Original thrust plates can often be reused, but they do get damaged and worn from debris.
Blue Thunder typically offers replacement thrust plates in bronze, and these are an optional upgrade for enhanced compatibility with the steel alloys found in roller cams. Roller-bearing thrust assemblies are also available, and are included with the Danny Bee timing belt drive system. I’ve had good luck simply running the factory parts in most applications.
Cam bearings for FE engines are babbit lined and are manufactured by either Durabond or Federal- Mogul.
Standard center-oiler FE blocks all use the same cam bearing set. The inside diameters are identical, but outside diameters get smaller as you go farther back into the block. This allows automated installation in the factory, so that one mandrel can be loaded with all five bearings and pressed into place. Side oiler blocks use a different drilling to feed oil to the rocker arm assemblies, but share the same dimensions with their more common center-oiler brethren.
Aftermarket blocks use a variation on the side-oiler cam-bearing design. As with the factory parts, all the journals have identical internal dimensions. But, in aftermarket blocks, the outside diameters are the same for all five bearings. The Genesis blocks use the same diameter as the factory number-1 bearing for all positions, but have Fordstyle side-oiler drillings. The Pond block uses the same strategy, but with slightly wider cam bearings throughout for greater load capacity. These require trimming the front cam bearing for distributor clearance after installation.
Federal-Mogul part number 1268M is the bearing set designated for Genesis blocks, and I have used it as a repair part for servicing damaged factory blocks when a cam bearing has been spun in its bore.
Roller cam bearings have been occasionally used in Super Stock level engine builds. The aftermarket blocks have additional material in the cam tunnel, making installation easier. The parts designed for 460-style engines can be made to work. The benefits of the roller bearing conversion are small, difficult to quantify, and often disputed, but it is a viable repair to a damaged block that may otherwise be discarded.
Selection Criteria: Lifter Type
First you need to decide on the lifter style for the engine. There are four basic options: hydraulic flat tappet, solid flat tappet (also termed “mechanical”), hydraulic roller, and solid roller. Each variation has advantages in certain types of use.
Keep in mind the fact that flattappet lifters rotate against the cam by spinning in their respective bores; it is not a sliding contact. The bottom of a so-called flat lifter actually has a crowned profile that works in concert with a taper ground onto the cam lobe to promote the spin. You can see and check that radius by holding a pair of lifters against each other “foot to foot” in front of a light background. The profile will be readily visible. Important note: Lifters that are truly “flat” are worn out and should be replaced.
Roller lifters do not rotate in their bores—they actually have a bar linking two lifters together to prevent rotation. They use roller bearings that ride against the cam. The cam lobe is thus ground flat without a taper. The lifter’s roller has a small radius ground into it to accommodate any minor variance in lifter-bore geometry.
Hydraulic Flat-Tappet Lifters
These lifters are the original equipment in the vast majority of FE engines. These inexpensive, quiet, and reliable lifters perform perfectly well in most street-oriented applications in which strong low- and midrange performance with minimal maintenance is desired. The FE pieces share the same .874-inch diameter as other popular Ford lifters, but common Ford lifters do not have an oil hole in the pushrod seat. This is because the traditional FE does not oil through the pushrods (the routing path is covered in detail in Chapter 5).
Hydraulic lifters operate with an inner plunger that floats on a cushion of oil within the outer shell. Oil is fed under pressure into the cavity separating the two sections and exits through the clearance between the inner and outer parts (or through the pushrod feed hole if so equipped). A check valve prevents oil from exiting through the feed orifice. The controlled leakage allows the lifter to run with a small amount of preload, which takes up any clearance in the valvetrain, and to compensate for wear. Most lifters will have roughly .100 inch of plunger travel between the upper retaining clip and the bottom of the cavity, with the desired operating position centered in that range.
Hydraulic lifters for the FE fall into two groups: the stock replacement parts or the so-called “anti-pump-up” race styles. In reality, the only major difference between lifters is the use of a heavier-duty retaining clip on the performance parts. This clip allows the performance parts to operate at or near zero preload without the risk of the lifter coming apart. While these are stronger and safer than standard parts, they do not offer a dramatic performance advantage. Perhaps a couple hundred RPM can be gained from running at zero lash, but any wear or temperature-induced dimensional change results in noisy operation and the need for adjustment. Hydraulic lifters were installed to avoid those issues in the first place.
Hydraulic Roller Lifters
These lifters combine the lowmaintenance features of the traditional hydraulic lifter with the rollerwheel design. These offer reduced wear, reduced frictional losses, and access to some enhanced cam profiles— plus break-in is not required. With the reduction in extremepressure additives in modern oils, notably less zinc and phosphates, the break-in period on flat-tappet cams has become a much larger issue than it was in the past. While successful break-in is certainly achievable without a lot of drama, the hydraulic roller retro-fit is an inexpensive way to completely bypass the issue.
Hydraulic rollers were never installed in any factory FE applications. The engine was discontinued long before these came into production. But the aftermarket has responded to the current demand by offering new parts that drop right into a normal FE block. The lifters use a link-bar design to prevent rotation, which is similar to solid-roller applications. All that is required are the lifters, cam, and custom-length (shorter) pushrods. Since FE hydraulic rollers are newer parts, they have the ability to oil through the pushrods if desired. A true FE roller lifter has the oil-feed hole perpendicular to the roller axle. A lifter intended for a 460 engine has the oil hole in-line with the axle, and puts way too much oil up to the rockers if used with the TD system.
The hydraulic roller lifters are large and heavy, and the only downside is an effective limit on RPM. Combined with the hydraulic design, they are best suited for moderate-RPM street engines with cams intended for a peak RPM at or below 6,200. In dyno testing, I’ve seen a pretty dramatic power drop off once the valvetrain control is lost on hydraulic-roller installations. Adding more spring pressure helps, but the hydraulic design can only accommodate so much pressure before becoming noisy and inconsistent in operation. There are ways to work around the limitations but unless race rules mandate the use of a hydraulic lifter, other types are better suited for those needs.
Solid Flat-Tappet Lifters
These lifters are the best choice when you are trying to make horsepower on a budget. They allow the 7,000-and-up-rpm levels that fall within the capability of the traditional FE block architecture. They are simple, inexpensive, and easy to install.
The solid flat tappets used in original FE engines have a “dumbbell”- shaped design, with a reduced diameter through the center of the lifter. There is no real advantage to these, but they’re still considered the “normal” FE solid. If you are intending to oil the rockers through the pushrods for the TD- or Jesel-style rockers, you need to use common small-block Ford solid lifters.
The downsides to a solid lifter include the need for careful break-in and proper high-zinc oil, along with the requirement for periodic lash inspection and adjustment. In addition, a solid lifter accelerates the valve off the seat very quickly because of edge contact against the cam. However, the shape of the lobe limits its opening rate once in motion.
Solid Roller Lifters
These are the preferred choice for serious high-horsepower applications. The basic design allows virtually unlimited RPM potential, and it tolerates (and requires) very high valvespring pressures. The cam profiles for solid rollers can be extremely aggressive with very high valve lifts—the roller can accommodate radical lobe designs. As the diameter of the lifter’s roller increases, the cam can become even more radical with improvements in both cam-to-lifter geometry and durability due to the larger parts.
The standard FE lifter diameter is the same as other Ford engines at .874 inch, but I have gone to .904- inch diameters in serious race applications. Larger-diameter lifters offer advantages in terms of strength, and on flat-tappet cams they allow more aggressive lobe profiles. You can use bronze lifter bore bushings to correct for any variances in lifter-bore geometry, although I’ve had good success just running against the block’s castiron bores. I see far more lifter-borerelated issues in older blocks from wear, moisture, and rust than I do in new replacement blocks.
The link bar is the most common roller-lifter design used in FE applications although other options do exist for high-end race engines. In order to send oil through the pushrods, you need to use appropriate FE lifters. The oil-feed hole on the FE lifter is at a 90-degree angle to the roller axle. Lifters from a 460 do physically fit, but the oil-feed hole is parallel to the roller axle, and sends far too much oil to the valvetrain when using pushrod oiling.
Cam Specs: Lift, Duration and Lobe Separation Angle
Cam specifications are given in valve movement increments. The various camshaft manufacturers provide the lift as well as duration specs, and most builders select a camshaft based on those numbers. The manufacturers provide gross valve lift, an advertised duration number, durations at .050-inch lift, and the lobe separation angle. This is good and useful information, but only a small part of camshaft lobe design. Professional cam designers work with lobe acceleration rates and opening/ closing events to arrive at the desired valve motion. The duration data and lobe separation points are thus an output from the effort, rather than an input. Therefore, while directional information can be derived from those specifications, you cannot assume that they are the entire story. Context is the key in comparing similar cams.
Lift is the maximum distance that the valve is moved from its seat, measured in thousandths of an inch. Gross valve lift, in increments of 1 inch, is determined by multiplying the cam lobe lift by the rocker ratio. This definition includes a lot of assumptions. First, the rocker ratio must be accurate, which is rarely the case. Next, this does not reflect the impact of valve lash. Last, the valvetrain always has some flex or deflection. It is not unusual to see considerably less actual lift when it is measured at the valve. Checking lift at each spot in the valvetrain tells you where the loss occurs by comparing your actual measurements to the mathematical ideals. Reducing deflection through use of stronger rockers, heavier-duty pushrods, and better mountings yields a significant improvement in both performance and durability.
If your valve lift is beyond the best flow range of your heads in a race engine, that is acceptable; but the port should not become turbulent or “back up” at the higher lift. This is because of the next variable, which is the amount of time that the valve can be held open at that peak level for maximum flow through the port.
Duration is the amount of time that the valve is open, as measured in crankshaft degrees. Since the crankshaft turns twice as fast as the camshaft, the number of degrees quoted is comparatively large, as 720 crankshaft degrees occur per one full turn of the cam. Advertised duration numbers are of nominal value because there is no real standard for the measurement—some cam companies use .002-inch lift for this measurement, others use .006- inch, others a “zero” base. The “duration at .050 lift” specification came about as a method of industry standardization—a way to compare cams from different suppliers. In the crudest of simplifications, the duration determines the operating RPM range of a camshaft.
Duration numbers (both advertised and at .050-inch lift) are useful for guidance but not definitive when comparing cam profiles. Various software programs can get you “close” on basic cam selection using these values, but plotting the full range of valve motion throughout the lift curve is the only accurate way to compare cam lobes. You can easily find two cam lobes with comparable lift, advertised, and “at .050” numbers, but they are significantly different at every other point in the range of motion. Comparing cams would be better done with a graphed curve showing durations at, for example, .100- .200-, .300-, .400-inch, etc. None of the large cam companies currently provide that level of detail for consumers.
This refers to the difference between the intake- and exhaustlobe centerlines as expressed in degrees. The basic assumption is that cams having a wide angle of 112 or more degrees are street oriented for a broad powerband and smoother idle, and that separation angles of 106 to 108 are race-car material with stronger peaks and a narrower power band. These ideas contain a grain of truth because a cam designer may use the same lobes and just move them around to change the tuning behavior. But they may also use completely different lobes to get the performance characteristics they desire, changing the angle values dramatically without changing the tuning behavior.
This is expressed as a number of degrees before crankshaft top dead center. This specification is used to install the cam at the proper position relative to the crankshaft, as desired by the cam designer. Cam lobes are not symmetrical, so the centerline is not going to be at the point of maximum lift. Instead, you find the centerline by locating a point .050 inch lower than peak lift on the approach and descending sides of the lobe, and splitting the difference. Installing the cam at the centerline position specified by the manufacturer should result in the opening and closing events occurring per specification. When cross-checking the opening and closing events, you must use the proper lifter. A solid lifter gives bad data if used for checking on a roller cam. The lobe’s flanks are completely different, even though the event specs may appear to be similar.
Advancing or retarding the cam changes the opening and closing events relative to the crankshaft, and alters the installed intake lobe centerline. It does not change the lobe-separation angle, lift, or duration values because those are ground into the cam itself. Altering the installed position by a few degrees can have either a very modest or a very significant impact on the way the engine runs. This is a tuning change with results that cannot be easily predicted, and therefore, you have to try it.
So How Do I Pick a Cam?
There are a few ways to go about the cam selection process. You can open a catalog and find the one that most closely matches your desires based on the manufacturer’s descriptive information. You can call the cam company’s tech lines and get more detailed recommendations. You can consult your friends, engine builder, or machinist to benefit from their experiences. Or you can recruit a professional cam designer to create a cam profile matched to your specific needs.
None of these are wrong, but some methods are going to have a better chance of success. The engine builder, cam designer, and tech department are all likely to have considerable experience with the kind of questions that arise. In the case of the designer, he or she works from your combination to generate a profile, while the tech group tries to match a pre-existing catalog profile to your application. Professional racing efforts almost exclusively use designer-specified solid-roller cams. The designer likely ends up with the stronger combination, but that increment of power comes with a cost that is potentially out of context for a more modest street-type build.
I’ll provide some general guidance as to what has worked for me in various FE engine builds. As noted earlier, this is not to be taken as definitive/prescriptive—but as general guidelines. Your results will certainly vary depending on the engine characteristics, including displacement and compression, as well as car variables, such as transmission, rearend gearing, and your own perceptions and expectations regarding drivability, sound, and power.
One statement that always holds true is that a larger-displacement engine can use a longer-duration cam with good results. Since most FE cam catalog recommendations are based on standard displacements, the now-popular stroker engines can comfortably go a step up in cam sizing without ill effect.
On 390-based 445-ci stroker engines, I often use the Comp Cams 282S solid flat-tappet cam.
With 236 degrees of duration at .050-inch lift, it delivers a noticeable but not too choppy idle at around 750 rpm. Gross valve lift is noted as .571-inch; subtract .022 lash to get a net lift of .549 inch. This is low enough to use the springs included with the popular Edelbrock heads, although I usually change them out for a double spring. Power peaks at about 475 hp at 5,500 rpm, with 503 ft-lbs of torque.
You will get more power and a higher RPM peak of around 6,000 by going to the Comp Cams 294S grind, with 248 degrees of duration at .050-inch lift and .605-inch gross lift. With about 20 more horsepower and more torque throughout the power range, this seems like a winning package, and it is. But it has a much choppier idle at 850 to 900 rpm and reduced low-RPM throttle response.
Putting a .668 gross lift, 248/252 duration at .050 solid-roller cam into a similar 445-inch engine got beyond the normal working range of the rest of the budget-oriented combination and only netted an extra 20 peak horsepower, while costing hundreds of dollars more. Of course the idle sound would stop you in your tracks from across a crowded parking lot, if that is one of your desired outcomes.
Now go to a 482-inch 427-based stroker and the situation changes dramatically. That same 236 at .050 282S cam we started with now delivered 537 hp at a similar 5,700 rpm. The torque also moves up to 574 ft-lbs at 4,200 rpm and idle is nearly smooth at 700 rpm. It also delivers excellent driving characteristics in a much tamer-sounding package until you hit the throttle and the torque takes over. But it runs out of steam pretty early for such a racy short block, making this a great engine for a Galaxie cruiser or a truck.
More common with large displacement engines are solid rollers. I’ve run the same .696-inch lift, 258/264 duration at .050 solid roller in multiple combinations with interesting and dramatically different results. With an 11:1-compression 482 and ported Edelbrock heads, this cam is good for a bit over 610 hp at 5,800 rpm, along with 620 ft-lbs of torque. Put that same cam into a 520-inch, 12.5:1, dual-quad, CNCported high-riser-head combination and you get up to 771 hp at 6,900 rpm, along with torque of 653 on the same dyno.
It seems counter-intuitive that the same exact cam would peak at a much higher RPM in the larger engine. What these results teach us is that the combination is the important item—not the individual components. The cam was not the limiting factor in the 610-hp engine; the heads were.
Working with the common catalog cam profiles, I can make some basic recommendations. These are dramatic simplifications, but provide a starting point. On a 390 engine, keep the duration at .050 down to a range between 215 and 225 degrees for a mild idle, and 230 to 240 degrees for a choppy one. As you go up in displacement, you can also go up a similar amount in duration and retain comparable driving and idle characteristics. An increase of 10+ percent in displacement to a 445 can easily handle a cam with 235 degrees of duration at .050 lift with very good street manners. It’s something of a non-linear sliding scale, though, and a 482-ci engine only wants around 250 degrees for a comparable performance range. A cam with durations of 260 degrees at .050-inch can support a 482-ci engine beyond 6,500 rpm, assuming the rest of the parts are strong enough for that operating RPM.
For lift, I try to keep the milder street combinations at or below the .600-inch-lift range. The reasons for this are twofold. First, the Edelbrock heads are delivered with a spring and retainer package oriented around a .600-inch peak lift. Second, keeping the lift within this window reduces likelihood for geometry issues or pushrod-tointake interference.
On more serious street/race engines, I push this to about .700- inch lift. This gets into an area where the manifold and valvetrain must be checked and corrected, but still delivers good durability once everything is properly set up. I use an oval-track-oriented valvespring and a tighter lash setting on roller-cam builds in an effort to get good component life. My feeling is that excessive loose lash and inadequate spring pressures are what really “kill” roller lifters in street use.
Going back to our original discussion on selection, there are no perfect, right answers. Engines cannot read. Use the information in this book and the most experience you can acquire and afford, and then make an educated camshaft choice. Then you’re going to have to go and try it in your car. Only then will you know whether it works to your satisfaction.
Written by Barry Robotnik and Republished with Permission of CarTech Inc
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