5.0 Mustang & Super Fords
Building A 600hp Street Mustang
From the engine and transmission to the chassis and rearend, we give you all the tips to help you build one
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Twenty years ago, if you were to tell someone that in the year 2000 there would be 600hp Mustangs roaming the streets, they would have deposited you into the nearest loony bin.
But here it is, the year 2000--and 600hp, daily-driven Mustangs not only exist, they are becoming almost commonplace. Thanks to advances in electronic fuel injection, centrifugal supercharger systems, and aftermarket engine management, building a 600hp street machine is relatively simple--if you select the right parts and use them in a well-conceived combination. That's why we're sitting behind the keyboard this time. If you've been thinking (even dreaming) of piecing together a street/ strip Mustang that will make you a legend in your neighborhood, this story is for you.
The stock block is sufficiently strong for 600hp use. Have it checked for cracks, and fit it with some high-quality main studs or bolts, like the one shown here. Deburring the block before machining is recommended, but not absolutely necessary.
The 5.0 platform is amazingly flexible. As such, there is almost no limit to the various combinations that will attain your 600hp goal--but there are really only two schools of thought: Build on the stock short-block and drive it/race it until it blows and then build something new, or start from scratch with an all-new engine. Lidio Iacobelli, owner of Alternative Auto Performance [(810) 463-0010] in Mt. Clemens, Michigan, says most of his customers prefer the former method, because it allows them to race/drive what they've got until they save for something better. "Then they'll usually want to build a stroker or a 351W-based engine," he adds.
Though not necessary to build 600 hp, strokers are a good way to build power, because most blockless kits are available for what it would cost to rebuild the stock short-block with quality components, plus you get the added benefit of extra cubes (and therefore more torque) to boot. Regardless of whether or not you decide to build a stroker, if you plan on using a stock block (as opposed to the bulletproof, but pricey R302), take it to a reputable machinist in your area, and have it Magnafluxed for stress cracks, bored, and torque-plate honed.
While you're at it, have the crank bore checked for correct alignment, and get it align-bored if necessary. You may also choose to completely deburr the block, using a high-speed grinder to remove all of the casting flash. This not only prevents junk from breaking off and falling into your engine, it prevents stress risers (and therefore cracks) from forming. This should be done before you have the machine work completed, however.
The next critical component to consider is the crankshaft. Lots of guys run the stock crank with amazing success (luck?) and many stroker kits are offered with an offset-ground stock crank. These are fine for lower-horsepower levels, but as power levels approach 600 or more, a better crank is advised. Aim for a kit that uses a steel crank, or at least an early-style, cast-iron 302 crank. The early 302 cranks have more beef in critical areas, and, as such, require that you have the flywheel and harmonic damper rebalanced to match the early 28 inch-ounce imbalance, as opposed to the 50 inch-ounce imbalance used in stock 5.0 engines.
Most stroker kits use aftermarket steel rods, but if you plan to build your own engine using the stock rods, you should still be OK. The stock rods are strong, and are widely believed to be safe for use in a 600-plus-horsepower engine. Have them shot-peened, Magnafluxed, fitted with ARP rod bolts, and resized. Don't bother having them polished, however, because for the money you spend here, you could almost afford a set of aftermarket steel rods. Forged pistons are a must, and unless you plan to build a high-compression (11:1 or higher), normally aspirated or nitrous'd engine, choose a flat-top, as these are what most aftermarket cylinder heads are designed around.
It's been said the camshaft is the brain of your car's engine, and is the one component that can make or break your combo. While this would be true of a naturally aspirated 600-horse 5.0, the camshaft really doesn't play such an important role in a supercharged/turbocharged application. A good cam will contribute to your 600hp goal, however, so choose one that has lift/duration figures that complement the heads you're running. With a supercharger/turbocharger at 10-14 psi of boost, you're only going to need a hydraulic-roller cam in the .510-.550 lift range with approximately 212-240 degrees duration at .050.
Finally, protect your investment with a quality aftermarket pan with extra capacity. Both Canton and Moroso offer excellent pieces that will clear the stock K-member and are available with dipstick tube kits. Not only will these pans keep your engine supplied with adequate lube under hard acceleration/braking, they can also provide "free" horsepower by preventing excess oil from roping on the crank. This is a cheap investment many enthusiasts overlook.
Cylinder Heads and Intake
It sounds like a cop-out, but almost all of the aftermarket aluminum cylinder heads are good enough to support 600 hp, especially in a supercharged/ turbocharged application. Most street-legal models flow 230-plus cfm or more on the intake side as delivered, and can flow more than that with a little port work. These include (but are not limited to) Edelbrock Performer, Trick Flow Twisted Wedge,Holley SysteMAX II, and World Castings Windsor. If you want a cylinder head that will support more than 600 hp, the Canfield, Edelbrock Victor Jr., Trick Flow Twisted Wedge R, and Brodix Track-1 are all good choices and don't require fabricated intakes or headers. However, keep in mind that these quasi-race heads don't come assembled, so you're going to have to spec out the valvesprings and so on, and do the assembly yourself, or have someone experienced do it for you.
Though the old standby GT-40 and Cobra intakes will work on a 600-horse engine in ported form, they are still not designed for this power level. A better choice would be the new generation of 5.0 intakes. The Edelbrock Victor, Holley SysteMAX II, and Trick Flow Track Heat manifolds will flow enough air for 600 hp and beyond, but keep in mind that most of these manifolds are not emissions-legal in all states, and may require a cowl-hood to provide adequate clearance.
There has always been debate over how big your throttle body should be. From our own experience, a 65mm throttle body is all you need for a stock or mildly modified engine, but we have seen for ourselves that a 70 mm will indeed make more power on a highly-modified 5.0, stroker, or 351 engine. Throttle bodies sized 75 mm and up are generally recommended for highly modified 347ci engines, which are beyond the scope of this article.
Mass air meters are another area where you're likely to get a different opinion from every tuner you talk to. Suffice it to say, most of the guys we've talked to over the last several months still like the 77mm Pro-M unit, although recommendations have ranged from a 73mm C&L all the way up to an 83mm Pro-M. If you go with a Pro-M, have it calibrated for the injector size you're running, and have it fitted with the company's Optimizer, another tuning aid.
The stock fuel system with a high-performance, in-tank pump can support an amazing amount of power, but when you approach 600 hp, a new fuel system is in order--and that means pump, lines (feed and return), and rails. Most of the tuners we've talked to recommend an Aeromotive, Paxton, or Bosch pump, coupled with a -8 line and 1/2-inch fuel rails and a -6 return line. Others, like Iacobelli, and Tim Matherly at MV Performance [(770) 725-7862] recommend even bigger stuff: Matherly likes a -10 line, and Iacobelli likes a -10 from the tank to the pump, then -8 from the pump to the rails and a -6 return.
At this power level on pump gasoline, a fuel-management unit isn't typically recommended, because a perfect air/fuel ratio throughout the engine's operating range cannot be assured. For this reason, most tuners recommend 42-pound injectors minimum (some recommend as high as 55 pounds) and some sort of programmable engine-management system. Yes, there are guys out there that make this kind of power using the stock computer--but unless you know one of them, or have vast experience tuning with the stock electronics, we wouldn't recommend it. Damaging an engine at this power level is easy if everything isn't just right.
The stock ignition system is also pretty impressive, and many believe it's good enough for 600hp just the way it is. However, most of the tuners we've spoken to recommend you upgrade with a better ignition box (the MSD 6A, 6AL, 6BTM, and Crane HI-6/HI-6TR seem to be the favorites) along with a hotter coil, like the MSD Blaster TFI or Crane PS-92. Many ignition manufacturers offer an aftermarket distributor as well, but it seems to be universally agreed that the stock unit will do the job. Low-resistance wires are a must (MSD, Jacobs, and Taylor all make good examples) and the spark plug heat range/gap should also be changed. Most tuners/racers recommend a plug that is two heat ranges lower than stock with a .030-.035-inch plug gap (supercharged/turbocharged). Some specific examples include Motorcraft ASF 22C, Autolite 3923, and NGK 8.
Header size/configuration is also a subject of debate. At this power level, most tuners recommend a 13/4-inch long-tube header, especially on stroker or 351-based engines. However, long-tube headers are not legal for use in California or states adopting its emissions guidelines, because they eliminate the pre-cats. Job Spetter of Turbo People always recommends 15/8-inch short-tube headers on street cars, even at 600 hp. "There's probably 8-12 hp difference between long- and short-tube headers," he says, "but the short-tubes make for a nicer-driving car, because the O2 sensors stay hotter and function better." So, if California emissions laws aren't a concern, and you want to extract every last pony, go with the 13/4-inch long-tubes--particularly if you're running a stroker or 351W-based engine. If you want better driveability and ease of installation, go with the 15/8-inch short-tubes.
Virtually every exhaust system manufacturer offers some sort of H- or X-pipe, and 21/2 inches is thought to be plenty for 600 hp. However, one of these pipes, coupled with a high-performance after-cat exhaust system (21/2-inch to 3-inch exhaust systems are preferred), will make for an exhaust note that is virtually unbearable for extended periods, and will get you noticed by your local police department in a big hurry. Contrary to popular belief, catalytic converters don't rob a lot of power--so if your stock H-pipe is in good condition and you want to save some money, keep it and bolt on a good after-cat system. Otherwise, a 21/2-inch cat H-pipe is a good upgrade, and will keep the exhaust note at an acceptable level.
What you plan to do with your 600hp street car will dictate the drivetrain components you need to run. If you plan to drag race it, you're going to need the best of everything if you want the car to last. If you plan mainly to drive the streets and occasionally go to the dragstrip on street tires, then you can get by largely on the stock trans and rearend, provided they're in good condition. Component failure has a lot to do with traction; if you don't have any, your chances of drivetrain breakage drop significantly.
If you want to upgrade your T5, the Tremec TKO is a good bet. It's strong, inexpensive, and bolts into your stock chassis without any fuss. Fit it with a steel bellhousing (like the FRPP M-6392-C) while you're at it, and you'll be in pretty good shape for street and occasional strip duty.
If, on the other hand, you plan to drag race a lot, the word we've received over the years is to go with an automatic, either an AOD or a C4. The Tremec, while certainly a tough trans, isn't designed for drag racing, and one too many missed Second-Third shifts will put an end to its faithful service. Sturdier, drag-oriented manual transmissions like the Jerico are up to the task, but they require modification and a working knowledge of clutch setups to function properly.
In most instances, a properly set up automatic with the right converter and a shift-improvement kit will not only be faster than a stick, it will be a lot cheaper and easier to maintain as well. If you plan to do a lot of street/highway driving, then the AOD will appeal to you, and there are a lot of shops out there that can make them last. If, on the other hand, your car will be relegated to dragstrip duty, then the lighter, less expensive C4 with a good converter and a transbrake is the way to go.
Opinions on driveshafts seem to vary; some of the guys we've talked to still run the stock driveshaft all the way into the 10-second zone, while others go with an aftermarket aluminum unit. We think the latter is the best way to go--an aluminum driveshaft like those offered by FRPP and Inland Empire Driveline Service [(909) 390-3030] are not only lighter than the stock unit, but much stronger as well. After all, when you consider the damage a broken driveshaft can cause, the extra cost of a race-oriented unit is certainly worthwhile.
Like all the other components we've talked about so far, the stock 8.8 rear can handle power levels that far exceed that of the stock engine, and needs only a few minor mods to make it stand up to the rigors of 600hp street duty. The first thing to go will probably be the stock Traction-Lok limited-slip rearend. Most of the tuners we've talked to across the nation like either the Auburn or the FRPP 31-spline truck carrier (M-4204-F318) as its replacement.
Next up are the axles. Without question, the most popular choice are the 31-spline axles offered by Moser Engineering. If you want the car to be legal (and safe) for racing, you should also fit the rearend with C-clip eliminators, which will eventually leak when subjected to street duty. Better yet, remove the whole unit and have 9-inch housing ends welded onto your 8.8. This allows you to use 9-inch axles with a higher spline count (31- or 35-spline) and bigger bearings/seals, which carry with them a locking collar that eliminates the need for C-clips.
What gearing you run is totally dependent on what you plan to do. If you're building a Ferrari killer or a Silver State Classic contender, then the stock 3.08s will be just fine. If you plan on street/strip duty, consider 3.55 or 3.73. Most of the Mustang mavens we've talked to prefer anything from a 3.73 to a 4.10 for an artificially-aspirated drag car with 28-inch-tall slicks.
Chassis and Suspension
It's been a while since we talked to anyone about specific chassis/suspension modifications and setup, so we called David Wolfe of Wolfe Race Craft (WRC) in Arlington, TX [(817) 275-8899; www.wolferacecraft.com]. Whether or not you've heard of Wolfe, you're already familiar with his work; it was his chassis that enabled Doug Mangrum to be the first Pro 5.0 in the 7s. A variety of other racers including Jon Yates, Job Spetter Jr., Jimmy LaRocca, and Lou Proto use Wolfe's components. A chassis-tuning prodigy of sorts, Wolfe is self-taught, and started building his first car when he was only 14. Six years later, he sold that first car to open Wolfe Race Craft in 1991, and he hasn't looked back since. Today, many still can't believe Wolfe knows what he does, but his products and tuning techniques speak for themselves.
If you plan on going drag racing, the first thing Wolfe recommends is weld-ing the torque boxes completely. "The unibody is the strongest thing in the world," he says. "Indy cars use unibody construction, and so do airplanes. The only weakness the Mustang has is that it's spot welded. Take the rearend out, and weld up every crack and seam. Once everything is welded properly, the stock torque boxes are more than adequate." He even sells a prefabbed plate that welds to the bottom of the box for added strength.
By Wolfe's own admission, the upper and lower control arms he sells may be overkill for a street/strip car. But as he points out, you're only going to step things up later on--so you might as well do it right the first time. WRC upper control arms are double adjustable, while the lowers are single adjustable. Both are fabricated from chrome-moly steel, and feature Heim joints rather than bushings to eliminate any deflection.
These control arms are used in conjunction with Wolfe's anti-sway bar, which he says is what really makes Fox- chassis cars quick. "You know how you see all these cars leave with one wheel in the air, and they look like they're going for the guardrail? The anti-sway bar eliminates that. Our customers typically drop between 3- and 7-tenths of a second [in the quarter-mile] with this bar in place in high-horsepower applications."
To round out the rear suspension, Wolfe recommends a set of good adjustable shocks (he won't specify a brand) and the stock springs. "Running the same spring rate from side to side is crucial," he stresses. "Some kits have a biased spring rate in the rear that places more weight on the right rear tire. It works well on the launch, but it makes a mess at the top end. As the car gathers speed and starts to settle down, it becomes sensitive to the spring bias, and can handle erratically. Everyone wants their car to leave straight, but in this case, the cure is worse than the disease."
Like so many other Mustang specialty shops, WRC offers weld-in subframe connectors, but they have two flavors--standard (what you're used to seeing) and through-the-floor. The through-the-floor models require that a slot be cut in the floorpan so the top portion of the large connector can pass up through it. The floor can then be welded to the connector as well, once again taking advantage of the unibody's strength. These alone are enough to stiffen up most street/strip 'Stangs, but if you're going racing, then you'll need one of Wolfe's rollbar or rollcage kits. If the idea of fabricating or notching your own rollcage intimidates you, you're going to love this: WRC rollbars/cages are available pre-bent and pre-notched. "All you do is assemble it inside the car like a jigsaw puzzle, and weld it in," Wolfe says.
Finally, Wolfe offers a few tips for the front suspension setup. "The front of the car is actually where the run starts, not the rear like most people think," he says. "The first thing to remember is the less power you have, the looser you want the front end to be. With a lot of power--1,000 hp and more--we limit the front-end travel and make it tight with adjustable struts. This stops the car from wheel-standing and leads to a quicker 60-foot time. For a 600hp car, I wouldn't limit the travel, but I would put some adjust-able struts up there. Also keep in mind that the car will always go faster on a good track with the front end tight; it will go faster on a bad track with it loose." A tubular K-member, Wolfe says, is optional. "The benefit (of a tubular K-member) is that they save you 75 pounds or more, and they usually relocate the lower ball joint forward about an inch, which increases positive caster and improves high-speed stability."
When it comes to the wheel/tire combo, Wolfe recommends sticking with the tried and true. A 10.5x28.5-inch slick mounted on a 10-inch-wide, lightweight racing wheel is all you should ever need.