Tom Wilson
December 1, 2002

Horse Sense:
Some guys want a cam with a lumpy idle but near-stock driveability. Well, forget it. Long duration and overlap are what give a cam that racy idle and blazing top-end horsepressure, along with lousy mileage, poor low-rpm power, and annoying driveability. You can't really have one without the other, especially on a computer-controlled EFI engine that does its best to smooth out the idle.

Got a hankering to power up your Pony? Been through all the bolt-ons and still looking for more? Ten pounds of boost not enough? A camshaft may be what you're looking for.

Camming 5.0 H.O. engines is more popular than ever, and there are some great choices available. In fact, there are so many camshafts for small-block Fords that we've polled the industry to see what the experts recommend for a few popular 5.0 combinations. Besides getting the shortcut to some promising 5.0 cams, the process has given us insight into the interesting and challenging world of cam operation and selection.

Opening Events
Truth is, the stock cam in your 5.0 is-if a bit tame by today's fire-breathing performance standards-a fairly nice piece already. Ford uses a steel camshaft with hydraulic roller lifters. The hydraulic part means the valve adjustment is automatically made with each valve event, saving us all from periodic valve-lash adjustments. Once a fair source of man/ machine bonding, lashing a V-8-especially when the upper intake manifold must be removed to access the driver-side valve cover-is definitely more chore than high-tech tinkering. We'll take the hydraulics, thank you.

Choosing a cam is all about knowing what you want from your car. Drag racing, for example, calls for a high and typically narrow rpm range to work with the short rear-axle gearing. This isn't exactly fun in a daily driver, so the trick is deciding just how racy to be. All cam makers report customers always ask for too much cam because they crave the high-rpm rush. Of course, two weeks later, most customers are ready for something a little more civilized on the street.

As for the roller part of the lifters, Ford put those there to reduce friction and thus increase gas mileage. By holding down your right foot, you can translate this mileage increase into more horsepower, so no one is arguing with the roller lifters. Roller lifters also allow more aggressive valve events. In other words, the valves can be opened and closed more quickly when using roller lifters. This increases power.

All 5.0 roller cams are steel, not cast iron. The combination of durable steel and roller lifters means cam and lifter break-in is a nonissue. Changing 5.0 cams means not having to bite your nails to see if a lobe went flat or a lifter collapsed during the critical break-in period, because with roller lifters, there isn't any break-in. All these things make the stock camshaft architecture a fairly good power producer while still offering a smooth idle. We've seen some impressive power from stock-cammed 5.0s, especially the supercharged variety.

The Specs
That said, an aftermarket cam-shaft could significantly boost engine output, more so than many of the simple bolt-ons. This is because the camshaft controls so much of what ultimately happens inside the combustion chamber.

Think of the camshaft as a mechanical computer for the intake and exhaust valves. The camshaft tells the valves when to open, how fast to open, how far to stay open, how long to stay open, when to close, and how fast to close. These are vital engine power-building parameters.

Open-tracking and other road-racing cars are easier to cam because the power that's fun on the track is just a hotted-up version of what's fun on the street. A broad torque band that pulls off the slower corners is a must, along with a little extra-high-rpm oomph on the straights.

To get started on specifics, the stock cam in 5.0 H.O. engines, while varying slightly in detail over the important '86-'93 period, is nominally the same. Its important specifications are listed below.

VALVE LIFT DURATION LOBE
CAM INT./EX. AT 0.050 IN SEPARATION
Stock 5.0 0.444/0.444 210/210 115

In other words, the stock camshaft opens both the intake and exhaust valves 0.444 inch at maximum valve lift. Both valves are open 210 degrees of crankshaft rotation when measured from 0.050 inch of valve lift (an industry standard), and the distance between the maximum lift of the intake cam lobe to the maximum lift on the exhaust lobe is 115 degrees.

While none of the cam specifications such as duration, lift, and so on can be seen in any precise way, this shot of an intake and exhaust lobe hints at what lobe separation angle is. It's the distance, in degrees, between the maximum opening point of the intake and exhaust lobes. Expect a 112 or possibly wider figure on cams for computer-controlled 5.0 engines. Any less and there isn't enough vacuum at idle to accurately signal the computer, and the idle control goes haywire.

For a hydraulic-roller camshaft, these specifications are relatively mild-the valve events are not severe so there is room for more lift and duration. Note the lift and duration are identical on both the intake and exhaust lobes. This is called a single-pattern camshaft. A dual-pattern cam, as often specified for Ford heads, has more lift, more duration, or more of both for the exhaust than the intake. This helps compensate for the so-so exhaust-port flow characteristics of most Ford cylinder heads.

Finally, the lobe-separation angle of 115 degrees is toward the mild side of the 108- to 116-degree range in which Ford cams often run. This reduces valve overlap-the time when both the intake valve and exhaust valve are open-which promotes a smooth idle, lower emissions, and lower-rpm power. It also works relatively well with forced induction because less of the intake charge is blown out the exhaust during the overlap period. This is one reason why the stock 5.0 short-block does so well with the typical street supercharger kit. On the downside, the relatively wide lobe separation is a natural limiter to high-rpm power. It's one reason why stock 5.0s become lazy past 5,500 rpm.

More Lift for the Duration
To get the latest on 5.0 H.O. cams, we talked to the big cam companies, along with some well-respected tuners who offer their own Mustang grinds. To corral the discussion into a workable size and format, we approached each outfit with four hypothetical engines to cam. See the Our Engines sidebar for the engine specifics before checking out what our experts have to say. While we could have gone on and "built" one with nitrous, turbo, positive-displacement blower, and ultra-rpm, naturally aspirated versions of the 5.0, we figured our four variations on the theme cover most of the market, and thus give a strong indication on what your particular engine might need.

Anderson Ford Motorsport
We're always happy to talk with Rick Anderson about Mustang engines, thanks to his nonstop dyno'ing and seemingly endless real-world tuning experience. In this instance, however, we sort of wish we could pick Rick's brain a little more in depth, as he's not keen on detailing his camshaft specifications. So, no lift and duration figures from Rick, but plenty of good recommendations on combinations.

Many 5.0 enthusiasts cam a nearly stock engine, and that's fine. But the 5.0 engine is also seriously in need of improved intake and especially exhaust ports, so aftermarket cylinder heads are a big help too. If your budget can handle somewhere under $500 for some power mods, go ahead and cam up. If you're working yourself up through a couple thousand dollars worth of power mods over a year or so, you could add heads, such as this inexpensive GT-40P, intake, throttle body, etc., then finish off with a cam specific to the combination you build.

Rick has packaged his tuning experience into a series of camshafts sold through Anderson Ford Motorsport. For Mustangs, he says, "I've got 17 naturally aspirated cams, and I've got 12 supercharger applications. Those are our basic numbers. Our hottest sellers are the N-41, N-31, and B-31."

Rick is a fan of high rpm in 5.0 engines, and he says his customers have relearned what their fathers already knew with their 289 Hi Po Mustangs-revving small-block Fords to 6,800 rpm is addictive fun. To that end, Rick is running steep rear axle gears-his own street machine 5.0 has 4.88s-and says that aside from reduced fuel mileage, he's found no other downsides to revving 2,600 rpm in Fifth with 28-inch tall tires at a 70-mph freeway cruise. Clearly his aim is not a mildly warmed-over daily driver, but rather a more serious Saturday night special that gets the job done at the strip and looks wickedly mean on cruise night.

For the Bolt-On engine, Rick suggests 3.73 gears and his N-41 cam. "That will pull real hard to 6,000, and drive real nice at 1,800-1,900 rpm. It works great with 4.10s... That's about the wildest you can do with stock pistons." For cylinder heads on such an engine, he figured on an Edelbrock Performer with 1.900-inch valves, Twisted Wedge or equivalent.

"If we went to 3.55 gears... go with the N-412. It has a broader powerband, and drives nicer down lower, but it won't make as much power in the 5,000-6,000-rpm range." Rick notes both his recommendations are for stick cars: "They'll work in automatics, but I'd like to see 2,800-rpm stall on the converter and 4.10 gears."

For the Well-Developed engine, Rick wanted to know which specific intake and gears the combination would be running. Given his N-71 cam, he says, "4.30 gears and shift at 6,500 rpm. If you want 4.56 gears, go to the N-91 cam."

To explain the steep final drive gears, Rick says, "We run 28-inch-tall street tires, which knock the gearing down a little more than one size. Most of these cars run 26-inch slicks (at the track) so the gearing is nice on the strip and not so bad on street gearing... This is with the Holley or Track Heat intakes with these cams. If you ran the Victor with the N-91, it's another 15 hp better.

"I have one gentleman with what we just described, and he runs 10.90s, a really beautiful '93 Cobra. These are all for street cars..." To run an automatic you "would have to have a 4,000-rpm converter, but for a stick it's not really too crazy."

Moving on to the blower engines, Rick points to his "B-31 cam for the bolt-on, short-block guy. It works great up to 6,500 rpm and has good piston-to-valve clearance. You can run that with 3.55 gears and it still runs real nice."

When putting the centrifugal on the Well Developed engine, Rick reaches for his B-41 cam.

In general, Rick says he looks mainly at the camshaft, head/intake, and rear-axle gear combination when making a cam selection. "Those three have to work together," he says.

Comp Cams
At Comp Cams, we had the good fortune to hook up with Billy Godbold, who, besides having a wicked sense of Southern-fried humor, is Comp's chief cam designer. Even better, Billy and one of his compatriots at Comp owned 5.0 Mustangs back when they were developing the camshafts for these cars, so he had plenty of firsthand experience to relay.

Billy made one especially pertinent observation: Selecting cams for street engines such as our examples is "75 percent about fitting it to the engine and 25 percent about fitting it to the person. A vehicle like this is a guy's passion. He should have a picture in his mind about what he's trying to do, and we should try to mold the cam into what the person is expecting out of it."

To meet expectations from our Bolt-On engine combination, Billy figured on an XE 266 HR grind, as sold on cam PN 35-514-8. This Xtreme Energy cam measures 216/224 degrees of duration at 0.050 inch of valve lift, 0.544/ 0.555 inch of valve lift, and uses a 112-lobe separation angle. This was the cam Billy had in his 5.0, and he rates it as "the perfect cam for the car the way it was made. It's the cam they should have come from the factory with."

If anything, Billy found the cam strong on torque at low rpm. This is especially the case if stock-size tires and a bit of gear are in play, as tire smoke easily follows. But this willing low-end pull illustrates how this cam will have no holes or flat spots when the throttle is suddenly dropped at 2,000 rpm in Fourth gear. It's quite driveable.

Still for the same Bolt-On engine, but pedaled by a more aggressive driver-someone who maybe goes to the strip six times a year-Billy says the next larger cam, the 35-518-8, is the way to go. This cam trades some of the 514 cam's extra torque for extra top end. "It didn't lose torque to the stock cam," Billy says. "It just picked up on top. It's for the guy who wants more e.t. and for it to have a little more sound. You might get a little bog out of it, if you're real low in the rpm range, below 2,000 rpm. But it will pull strong right up to the rev limiter."

For the record, the 35-518-8 cam uses the XE 274 HR grind, which measures 224/232 degrees of duration, 0.555/0.565 inch of lift, with 112 degrees of lobe separation. Billy pointed out that the ramps on this and the 514 cam are identical, so it's just a larger lobe, really.

Stock and mildly improved 5.0s-and that covers the vast majority of street-driven Mustangs-do fine with an off-the-shelf camshaft. But when you reach this level-with tons of internal engine mods, a blower, and oddball intake manifold-it's time to consider a custom-ground cam. A redline of 6,500 rpm or higher is an excellent clue to investigate custom camming.

For the Well-Developed engine, the first thing Billy wanted to know was if the computer had a chip or had been reflashed for a higher rev limiter. "If he hasn't upgraded the computer, if it's stock, I'd look a lot at the 35-518-8 again. But if with a chip or carburetor, then I'd go with the next larger cam, or consider going to a flat-tappet or solid-roller lifter.

"The next larger [cam] is the 35-522-8 with the XE 282 HR grind." That gives 232/240 degrees of duration at 0.050 inch, 0.565/0.574 inch of lift, on 112 degrees of lobe separation. Billy says this cam is a bit faster than the 518, but it's less well-mannered. It's a better choice for the guy wanting a "big, old snotty idle." The 518 is for the guy who wants excellent power but also demands some sophistication from his engine.

"The reason we don't like it [the 522] with the stock computer," Billy says, "is when you pull up to a light with the headlights and air conditioning on, it's liable to die on you. It will do some weird things. Plus, the big cam makes big power right near the stock fuel cutoff. But if you can extend it out to 6,500 rpm, you can help your power average with it."

Stock Ford rockers are bad from a performance point of view. When stepping up the cam, moving to roller rockers such as these is an excellent addition. You'll gain power from reduced friction and cool the oil temp some as well.

It's at this state of tune-when the engine is needing to turn around 6,500 rpm-that Billy wants the customer to consider a custom grind camshaft to best extract what each engine combination has to offer.

Moving on to the supercharged versions of the Bolt-On and Well-Developed engines, Billy had two quick recommendations. For 8 pounds of boost and easy bolt-ons, he spec'd a Nitrous HP cam with the NX 274 HR grind. The part number is 35-556-8 and the specs are 224/236 degrees of duration; 0.555/0.570 inch of lift; on a slightly wide, 114-lobe separation angle.

For 10 pounds of boost on the Well-Developed engine, Billy moved up a notch to the 35-560-8 part number cam. It uses the NX 282 HR grind, which gives 232/244 degrees of duration, 0.565/ 0.580 inch lift, and again uses a 114-lobe separation angle.

Changing the camshaft is a moderate-size job, but one the average enthusiast can do at home with the usual hand tools. Most of the cam companies have excellent how-to videos and instruction manuals covering the job.

Both of these cams employ the identical strategy of using about the same overlap as the naturally aspirated cams, but they do open the exhaust sooner to help scavenge the exhaust more efficiently. As Billy puts it, "Some people put more exhaust [lift and duration] on a blower to get the exhaust out, but the exhaust is going to get out anyway. The piston will push the exhaust out, but that takes horsepower. Now, the exhaust you get out before the piston reaches bottom dead center, you get that out for free. With the blower, there's more pressure in the chamber, so there's a faster burn rate, and theoretically the combustion is finished sooner. So you can open the exhaust sooner, and free up some horsepower by getting some of the exhaust out before the piston starts coming up."

Crane Cams
Chase Knight is the cam and valvetrain manager at Crane Cams. With Crane's huge experience in the entire spectrum of automotive performance, he was a great one to talk to about selecting camshafts. Generally, Chase says he looks mainly at an engine's displacement, compression ratio, whether the cylinder head is iron or aluminum (both for material properties and how aggressive the cylinder head might be on airflow), induction system type, to some degree what the exhaust system is like, and, of course, the intended application. If the engine is force-inducted, then how much boost is available, and for high-altitude applications (5,000 feet and higher as typified by Denver), then at what altitude will the vehicle normally run.

Crane's recommendation for our hypothetical engines is limited to just three cams. This is not unexpected from a cam giant such as Crane. For relatively mild engines such as the ones we've specified, Crane knows splitting lift and duration hairs has limited value in a mass market. With so many customers, there are just too many variables. If a custom cam is what you'd like, Crane definitely has that option covered too.

Mild to wild, nearly all cam-shafts cost the same. That means cost is not the deter-mining factor in cam selection; choosing the right cam for your tastes and power requirements is the main task.

Chase says for the Bolt-On engine, "You could use either a 444221 cam-shaft with 1.6 rockers, or a 444225 camshaft with 1.7 rockers." These are the old Compucam 2030 and 2031 part numbers. The 444221 offers 216/220 degrees of duration, 0.533/0.544 inch of lift, and is built with 112 degrees of lobe separation.

For all the other engines, meaning the Well-Developed and the two supercharged versions, Chase recommends the 449811 camshaft with 1.6 rockers. He says this cam would be "excellent" in all these engines.

Specifications on the 449811 cam are 236/244 degrees of duration, 0.574/ 0.595 inch of lift, on a lobe separation of 114 degrees. This is a deep-breathing set of specifications, and we don't doubt it will make power. With big numbers such as these, you really want to make sure the valvesprings are healthy. Ford's 5.0 H.O. valvesprings are not known for their longevity-or lift capacity for that matter-and once they've gone past 40,000-50,000 miles, replace-ment is required. Otherwise, you'll simply be floating the valves when trying to rev up to where a cam such as this does its thing.

Lunati
There seemed to be some good understanding of the 5.0 Mustang engine at Lunati, where we talked with Kirk Millner. Interestingly, the company's 51014 cam for the 5.0 is Lunati's best-selling hydraulic-roller-lifter cam in the catalog, "by far," according to Kirk, so you know it's doing some small-block Ford business.

For our hypothetical Bolt-On engine, Kirk began by noting, "You're pretty restricted on the piston-to-valve on that motor. I try to keep them to the 0.525-lift range, which of course includes the 1.6 rocker ratio. And you'll need wide lobe separations to maintain manifold vacuum for the electronic fuel injection system.

"For that engine, I'd specify our 51023. That's 0.522 inch lift, 215 degrees at 0.050-inch valve lift on the intake and 224 degrees on the exhaust, with a 112 lobe separation. That is going to work right up to the 6,000-rpm range. At 6,200 you're probably getting past where that cam wants to work anyway.

"I have another cam-the 51014-that sells really well in that range. It's 0.500 inch on the intake and 0.510 on the exhaust, duration at 0.050 inch of valve lift is 218 on the intake and 226 on the exhaust, with a lobe separation of 112 degrees. If you had a touch more gear, I'd be throwing that cam at you."

Kirk pointed out that the 51014 is "the hottest thing in my book. It's so versatile. The only applications I don't like it in are an automatic, or speed density." For those cars, the quite mild 51013 works with the factory valve springs, has a "noticeable tone in the pipe," and works off idle up to 4,500-4,800 rpm. If the customer wants more than that in a speed-density car, Kirk tries to "sell them a four-barrel," as they won't be happier with a larger camshaft and speed density. The idle simply turns into a hunting disaster that would drive a saint mad with it's stumbling, hesitating shaking.

Moving on to the Well-Developed engine, we mentioned our specifications, which include 4.10 gears and a 7,000-rpm redline, something Kirk noticed right away.

"The first thing there that struck me as odd is the seven grand. It's hard to get a lifter that will stay on the cam at that rpm." Kirk went on to explain that current off-the-shelf lifters can't handle the combination of a light valvespring required for the hydraulic plunger in the lifter along with the juice lifter's necessarily high weight. As he puts it, "There's not a lifter built out there that will go over 6,800 rpm... You have to spring them very lightly, only 120 pounds on the seat-and from Ford, they're not even over 300 wide open. They just don't like rpm. They're a big, heavy lifter, and you have to spring it lightly because of that plunger. A lot of [pro racers] go in and modify the tappet, but you can't buy it yourself off the shelf."

While the stock cam has done well for tens of thousands of bolt-on Mustangs, a performance cam can really put the edge in your car's performance.

With that admonition in mind, we returned to the Well-Developed engine in detail. "Mid- to high-sixes, let's go with the 51025. That's 0.535 inch lift on the intake and 0.544 inch on the exhaust, duration is 224 degrees at 0.050-inch valve lift and 232 degrees on the exhaust. Again, a 112 lobe separation. I'll be consistent on my lobe separation angle on all fuel-injected camshafts."

For the Bolt-On with 8 pounds of blower boost, Kirk says, "We can still use the 51014, if not over 8 pounds... run it straight as it is, then let me put a little more lobe separation in to keep the blow-through down," if more boost was being used.

On the Well-Developed with 10 pounds of boost, Kirk was reaching for his 51012. This grind offers a fairly stout 0.544/0.560 inch of lift, 232/242 degrees of duration, and a lobe separation angle of 114 degrees. This is the first cam from Lunati with more than 112 degrees of lobe separation, the result of the higher boost. As Kirk says, "The more boost, the more lobe separation you'll need. Under 400 ci, keep it at 112-114. The blower is going to make the horsepower, we're just trying to get the cam close on."

As Kirk was clearly focused on the lobe separation angle, we queried him about its importance. The answer was the lobe separation angle played a large role in building manifold vacuum, and, "Manifold vacuum is everything [on computer-controlled EFI engines]." Without sufficient vacuum, "the computer is hunting the idle, going rich-lean, rich-lean, and the computer will never figure it out." Anyone who's suffered through a hunting idle on a 5.0 will readily agree with Kirk that a 112-degree lobe center or greater is a wonderful thing. That will keep the manifold vacuum high and the computer happy.

Panhandle Performance
While the big cam companies and mail-order houses like to sell off-the-shelf cams, most engine builders are much more comfortable working with custom camshafts. Some engine shops will sell you an off-the-shelf cam, but as specialists they know the secret to unlocking the most power from any combination is getting all the details as close as possible.

That's exactly what Mark Biddle at Panhandle Performance believes in, to the point where he does not sell ready-made cams, but rather deals strictly with custom cams. Understand that all but dedicated cam manufacturers do not grind their own camshafts. Instead, these builders work with a cam maker, who provides them with a cookbook of available cam lobes. The engine builder chooses the lobe, or grind, from the book. He can select what lobe separation angle he wants, as this is easy enough when the cam grinder sets up the grinding machine.

Given the pure custom nature of his cam business, Mark was ready to talk about what he looks for while selecting a camshaft rather than specific values for our hypothetical engines.

"Normally, I don't spec a cam without flowcharts on the cylinder heads," he says. "I want to know the intake-to-exhaust flow ratio on the cylinder head." Mark also needs to know "the weight of the vehicle, tire size and type, cubic inch, compression, any type of power adders, any type of idle characteristics they want, and where they want their power. Also, the lengths of the intake runners have a huge effect on the cam-shaft and where we put the lobe separation." Other factors are "the cylinder flow numbers, and how well the head flows depending on the cubic inches of the engine."

What it really boils down to for Mark is matching the cylinder head, intake manifold, and camshaft flow characteristics. If these three critical items are matched to each other, the power has to be at least close. In fact, Mark believes these airflow parts are so critical, he says he'd rather "match the cam to the rest of those two pieces than the rest of the combination. If those other two pieces are not right for what he's wanting to do, then his camshaft selection is going to be wrong as well."

Mark repeated what many cam experts had already told us, only more so. Much of cam selection comes down to what the customer wants and then giving it to him. "I get guys who call all the time. 'I have these parts, and do I get the B, E, or X cam?' And I say, 'Well, none of them.' I start to explain it to them, and usually they think I'm blowing smoke, and they say I'll call you if I want to do that [get a custom grind]."

Once the customer is ready to work on a custom-grind cam, then Mark has to take a fair amount of time to talk to the customer to find out what he wants and explain how he's going to get there.

"It's like a doctor [asking questions]. Once I had a doctor who talked with me for 45 minutes. He sat and listened." This surprised Mark, who had found most doctors spend their time running from examination room to examination room, rarely in the mood for listening. But as Mark's doctor told him, "90 percent of the time the patient will tell you what's wrong with him."

"So when the customer asks for a camshaft," Mark says, "I really try to listen to him to see what he wants out of the vehicle, rather than what I think he should have." After all, Mark figures, "What is not much to me is maybe a lot to someone else. It's really important to listen to what they want."

The time spent interviewing the customer is tough on the engine-builder's bottom line, though. "You're paying for the experience as well as the part [when buying a custom cam]. It's a tough deal on camshafts."

Mark gave us some of the specifics and how they affect his cam decisions. "The first application (our Bolt-On engine), and whether it's a five speed or an automatic, will affect the lobe separation. A five-speed will use a wider lobe separation, generally 2 degrees wider, all other things being equal.

"Generally, a slightly narrower lobe separation will help it come on the torque curve earlier, but a bit peakier. The same thing with a heavier car... [if] the car weighs 3,750 pounds, then the same thing; a slightly narrower LS will get the car moving faster. A wide lobe separation gives a wider torque curve. The narrower lobe separation will fall off a little earlier."

In the end, Mark says, "A camshaft, at best, is only a compromise. You have to compromise somewhere to pick up somewhere else."

Probe Industries
Mark O'Neil at Probe gave us the West Coast engine-builder's opinion on camming 5.0s. For starters, as an engine builder who gets constant business from guys rebuilding and stepping up their 5.0s, he sees nothing but 347s when it comes to camming, so we heard a lot about 347ci displacements. That's important, as a larger engine breathes more air, all other things being equal, so a 347 can use a notch more cam than a 302/306.

In general, Mark begins by asking a customer what he's doing with the engine. As it's been since the invention of the cam lobe, customers are always asking for too large a cam, so Mark sees a large part of his job as steering the enthusiast to at least "something he can live with."

When sizing a cam, Mark looks toward airflow, not rpm, as his guide. "How much air can he suck in?" he asks. "How big are the throttle body, intake, heads?" He wants to size the cam to his customer's components.

Mark doesn't want to base the cam on the car's rear-axle gearing. He's looking to size the cam to work with the torque curve the heads, intake, and other airflow parts are delivering, then gear the car to the rpm range at which the engine will necessarily run, given those components.

"The idea behind building an engine is simple," Mark says. "You have about 40 torque curves inside the engine, and you're trying to have them fall in the same plane. You can't do this, so you compromise until you get to something that will fit your design parameters. Then gear it to run your torque curve." In other words, Mark is pointing out the combustion chamber wants to make power at one rpm range, the intake manifold runners at another, the throttle body at another, the headers at another, the intake valve and seat at yet another, ditto the exhaust valve, and on and on. As always, it's the combination of parts that really counts.

For the Bolt-On engine, Mark says, "Our hydraulic roller 4017 grind-that's a 0.499/0.510, 212/225 on 112 centers. I'd use that on a mild 347." It might finally be time to point out that engine men talk cam lift and duration numbers like chassis shops speak in tongues about tires: just numbers, skipping such niceties as "lift" and "duration" for speed's sake. So, for the newer Mustangers in the audience, the Probe 4017 grind has an intake lift of 0.499 inch, an exhaust valve lift of 0.510 inch, duration figures of 212 and 225 degrees for the intake and exhaust, respectively, with 112 degrees between the intake and exhaust lobe centers.

Mark went on to say this cam would make "350-375 hp with 9:1 compression."

With a blower (on the Bolt-On engine), Mark says, "I'd go, on a daily driver, 0.510/0.534, 222/232 on 112 centers, which is a 4018 cam." Note that for the typical street blower Mustang engine, Probe increases the valve lift substantially, but increases the duration only modestly. This combination of lift and duration provides more airflow without leaving the door open so long the intake charge is blown out the exhaust port. This does mean the valves are banged on and off their seats a bit more violently, but as Mark is telling us here, a half inch of lift and 225 degrees of duration will work without valvetrain mayhem.

Mark says, "Our number-one seller-we use it in a broad range of engines-is 0.544/0.573, 228/238 on 112 centers... on a 347 with a Victor Jr... in the 7,000-rpm range, it makes a tick over 450-460 hp. In a bigger engine, it makes even bigger power. If there'd be any change there, it would be 1.7 rockers and leave everything else the same. Oh, you could futz around with lobe separation, but on an average range you don't have to mess with it.

"Fords have to have more lift and more duration, around 8-10 degrees of duration at 0.050 inch on the exhaust. This is a must. Typically we stack the lift on the exhaust about 0.020 inch on the Ford as well."

Addressing the blower versions of the Bolt-On and Well-Developed engines, Mark says of the Bolt-On engine, "We use the 0.544/0.573, 228/238 with 112 centers; this with 10 pounds of boost and hang onto your seat. Try to get a cylinder head that matches. If you don't care about smog, an Edelbrock Victor Jr. is the all-around best head to run. And if you do care, our Stage III-ported Performer flows the same as Victor Jr. It's technically not [smog] legal, but it [EGR, Thermactor] all hooks up.

"The part number on this cam is 4022. We put that in everything. The most notable one was a 508-inch engine in a '67 Mustang convertible with a five-speed. It has a smooth idle, and when a Honda kid pulled up alongside, the owner said he 'won't even waste the downshift.' It's just a wonderful camshaft."

While general camshaft practice has proven many times that selecting just when to close the intake valve is a critical point, Mark made the point that much of selecting a camshaft on Fords is getting the exhaust-valve timing correct. This is the reason why the lobe centers are sometimes adjusted. "Typical values for the lobe separation angle," he says, "are as low as 108 degrees and as high as 116 degrees; 112 are the most common. It's all about making the exhaust side work well."

In Closing
So there you have it, a sample of the cam industry's thoughts on improving typical Mustang 5.0 engines. We'll take this opportunity to remind readers that, in our experience, sticking with the stock camshaft is not a bad thing, at least for a while. The 5.0 H.O. engine responds well to upgraded cylinder heads, intake manifolds, throttle bodies, and so on. Even a blower coupled with a stock cam is an entertaining combination, and the driveability, quiet, and ease of passing emissions tests with the stock cam is unquestioned.

But there does come a time, when you have the bolt-on situation covered, that a camshaft is definitely an important step. Mild to wild good fun, there's a bumpstick just right for you and your combination.

Our Engines
We presented our cam experts with four hypothetical, but typical, 5.0 engines for them to select a cam.

1) Engine number one we'll call the Bolt-On engine. There are plenty of these running around, you'll agree. This engine uses a stone-stock short-block, so the crankshaft, rods, pistons, oil pump, block, and all that have never been touched. We decided to use mild, unported aftermarket heads, such as iron GT-40s or even aluminum Edelbrock Performers. A matching intake manifold, also unported, was specified, along with a 70mm throttle body, an aftermarket mass air meter, short-tube headers, and aftermarket high-flow cats and after-cat system. While these engines may have an electronic chip in them, their powerband is still below the stock, 6,250-rpm fuel cutoff, so we specified that, along with 3.55 or 3.73 gears, a five-speed manual gearbox, and daily driver status.

2) We'll call our next engine the Well-Developed engine. Here the short-block has been rebuilt and the top-end prepped for sporting use. That means a stock block, 0.030 inch overbore, good rods, after-market forged pistons, high-volume oiling, better aluminum cylinder heads with some porting, a prepped high-flow Trick Flow or such intake manifold, a 70mm throttle body, a large mass air meter, long-tube headers, an after-cat system, and an engine redline of 7,000 rpm. That means the power peak could reach as high as 6,500-6,800 rpm. This sort of engine typically still has to be streetable, but it's aimed at drag racing, slaloms, and open tracks. Thus, we counted on 3.73 or 4.10 gears and a five-speed.

3) Engine number three is the Bolt-On engine with 8 pounds of centrifugal blower boost.

4) Engine number four is the Well-Developed engine with 10 pounds of centrifugal boost.

Phone Lobes
Recognizing how involved it can be to select a camshaft, the major cam companies often provide various cam selection services via e-mail or telephone.

The typical drill is to answer a rather extensive questionnaire about your engine and vehicle-seemingly down to how much air is in the spare-then have the computers at cam central spin out the optimum number. The pros at these big companies work with cams 24-7, and we'll wager their guess at how fat your lobes should be is going to be better than your best buddy's choice, so give 'em a whirl.

Comp Cams offers CAM HELP at (800) 999-0853.

Crane Cams' Technical Service line is (386) 258-6174

Lunati's camshaft tech line is (901) 365-0950.