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Ford Mustang 5.0L Engine Horsepower ModificationsModding Your 5.0 With Bolt-Ons And Beyond From the July, 2010 issue of Muscle Mustangs & Fast Fords By Richard Holdener Photography by Richard Holdener
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From basic bolt-ons to turbos,... From basic bolt-ons to turbos, everything it takes to build serious 5.0L firepower is right here on the cart. Modern modular motors have a lot going for them, especially with the recent introduction of the new 412hp 5.0L variant. Sharp-eyed readers will no doubt recognize that the Blue Oval marketing department took a retro step back because the original 5.0L had, and still has, such a strong following. In fact, 5.0L guys are diehard, often dismissing the modern mod motor for its lack of torque and the inherent limitations on displacement thanks to the diminutive bore centers. Meanwhile, the trusty pushrod 5.0L has no such deficiencies, and can be taken to the high side of 370 ci with the proper combination of block, bore, and stroke. The limiting factor is actually the deck height. What the original 5.0L has over the modern machinery is also cost, as a 5.0L Mustang can be had for about the price of a decent value meal at your local fast food joint. Knowing boost and juice were... Knowing boost and juice were on the to-do list, we stepped up to a 4340 forged-steel crank from RPM. Working with the forged crank was a set of 4340 forged-steel rods (5.4 inches) supplied by ProComp. To illustrate just how receptive the original 5.0L is to modifications, we put one through the ringer on the engine dyno, running it with a myriad of modifications. We did eliminate a few tried and true mods, however, like the air silencer removal, mass air meters (we ran with a FAST management system), and underdrive pulleys. But it did allow us to run the full gamut of performance upgrades starting with a simple throttle body and ending with a complete turbo kit. Along the way we tried a pair of intake manifolds, performance aluminum heads and even nitrous. In short, it was a full day of dyno testing and part swapping, but what better way to spend the afternoon than watching the power needle climb and climb and climb? Not wanting to limit ourselves with a stock (junkyard) 5.0L, we built a 302 capable of withstanding our eventual boosted output. To that end, we assembled a 302 using a factory 5.0L roller block machined by L&R and assembled by Demon Engines. The short-block consisted of a forged-steel crank from RPM, combined with a set of forged rods from ProComp and matching pistons from Probe Racing. The flat-top pistons yielded a static compression ratio of 9.35:1 with the 61cc chambers in the stock heads. Probe Racing supplied a set... Probe Racing supplied a set of forged-aluminum flat-top pistons. The 0.040-over pistons, along with the remainder of the reciprocating assembly, were installed into a production 5.0L block. The pistons featured generous valve reliefs to allow for our high-lift Xtreme Energy cam. In addition to the stock heads, cam, and intake, the build up also featured new hydraulic roller lifters, a double-roller timing chain, and hardened pushrods (6.25-inch), all from Comp Cams. The stock E7TE heads had been previously modified to accept screw-in rocker studs, which we used with self-aligning roller rockers. We hoped to test stock rockers versus the roller rockers, but the modified heads would no longer accept bolt-down rockers. Other than the screw-in studs and a spring upgrade (to work with the Xtreme Energy cam installed later), the head ports, chambers, and valve job remained completely stock, meaning they performed just like a stock set would in terms of flow and power.  The short-block featured Fel...  The short-block featured Fel Pro PN 1011-2 head gaskets and ARP 7/16-inch-head studs. Note the use of a Meziere electric water pump, MSD distributor, and ProComp 28-ounce damper.  Stock 5.0L: 252 hp at 5,100...  Stock 5.0L: 252 hp at 5,100 rpm, 306 lb-ft at 3,300 rpm
First we established a baseline. We installed 36-pound injectors since we knew the power output would eventually exceed the flow of the stock 19-pounders. The motor was run with Lucas 30W (non-synthetic) oil, an MSD distributor, and a FAST XFI management system. Also present was a set of plug wires and fabricated valve covers from ProComp. Though we hoped to run the stock exhaust manifolds, a snafu resulted in us starting our baseline testing with shorty headers. The shorty headers make an interesting comparison to the long-tube Super Comp headers we eventually installed. Run with the air/fuel and timing dialed in for maximum power (13.0:1 and 36 degrees of total timing), the 5.0L produced 252 hp at 5,100 rpm and 306 lb-ft of torque at 3,300 rpm.  Hooker 13/4-inch Headers:...  Hooker 13/4-inch Headers: 261 hp at 5,100 rpm, 321 lb-ft at 3,400 rpm
We replaced the shorty headers with Hooker 13/4-inch Super Comps. Long-tube headers provide a tuning effect based on the primary length. Just like runner length in the intake manifold, the headers help scavenge the exhaust and therefore help draw in the induction charge. These pipes increased the power output throughout the rev range. The peak numbers jumped from 252 hp and 306 lb-ft to 262 hp and 321 lb-ft. The Hooker headers improved torque production by as much as 25 lb-ft at 3,000 rpm.  GT-40/AccuFab 65mm TB: 280...  GT-40/AccuFab 65mm TB: 280 hp at 5,300 rpm, 326 lb-ft at 3,400 rpm
The GT-40 intake offers a revised runner length and cross section. The tuning effect works on the induction side as the runner length and cross section combine to provide a minor supercharging effect. This ram effect greatly improves cylinder filling over the air drawn in by the simple downward stroke of the piston alone. Like the headers (only in reverse), this tuning effect is a function of the variables in the manifold, which must be optimized in the proper rpm range. On our mild 5.0L, the GT-40 intake increased output from 261 hp and 321 lb-ft of torque to 278 hp and 323 lb-ft of torque. These numbers were increased slightly to 280 hp and 326 ft-lb with the addition of a 65mm throttle body from AccuFab. The tuning effect is obvious in the power curves, as the stock (small and long-runner) H.O. intake produced more torque than the GT-40 up to 3,330 rpm...  Comp XE274HR Cam: 312 hp at...  Comp XE274HR Cam: 312 hp at 5,400 rpm, 349 lb-ft at 4,000 rpm
Next up was one of the author's all-time favorite 5.0L cam profiles, the XE274HR hydraulic roller cam offered by Comp Cams. The XE274HR cam (PN 35-518-8) featured a 0.555/0.565-lift split, a 224/232-duration split and an EFI-friendly (as well as blower and turbo) 112-degree lobe-separation angle. The author ran Crane's version of this cam in his personal 5.0L LX back in the day, and it works equally well in normally aspirated, turbo, and supercharged street combinations. The cam was chosen not for its maximum power potential, as the newer XFI cams certainly offer more power, but the XE274HR offers a near-ideal combination of drivability and power that is difficult to match. With sufficient valvespring pressure, head flow, and intake design, the XE274HR will rev cleanly past 6,500 but still provide sufficient idle vacuum, throttle response and even fuel mileage.  The 5.0L was first run with...  The 5.0L was first run with a stock five-speed H.O. cam. Hardly a performance piece, it was necessary to establish our bone-stock baseline. Comp Cams supplied a new set of hydraulic roller lifters, which we used with the production retainer assembly.  The stock E7TE heads had been...  The stock E7TE heads had been previously modified to accept screw-in rocker studs. The heads were run with 1.6-ratio, guided roller rockers.  We dusted off a production...  We dusted off a production 5.0L H.O. intake and stock throttle body. The ProM MAF was used as a simple radiused air entry since the motors were tuned using a FAST XFI management system. With boost in the cards, we replaced the stock 19-lb/hr injectors with a set flowing 36-lb/hr units from FAST. The stock fuel rail was used for all testing, including with the turbo motor.  Run in stock trim, the 5.0L...  Run in stock trim, the 5.0L produced 252 hp at 5,100 rpm and 306 lb-ft at 3,330 rpm. The first performance modification was to replace the shorty headers with a set of long-tube Super Comp headers from Hooker. The long-tubes improved output from 252 hp and 306 lb-ft of torque to 261 hp and 321 lb-ft. Gains offered by the Hooker Super Comp headers were as great as 25 lb-ft.  RHS CNC Ford Heads: 354 hp...  RHS CNC Ford Heads: 354 hp at 5,500 rpm, 378 lb-ft at 4,300 rpm
Having already replaced the upper and lower intake and camshaft, the next item on the to-do list was a head swap. We chose a set from Racing Head Service. The Elite CNC heads offered everything the stock heads couldn't, including aluminum construction to reduce weight and massive flow numbers that (according to RHS literature) exceeded 300 cfm at 0.700 lift. Basically the flow rate of these RHS heads was nearly double that of the stockers. The RHS heads were outfitted with valvesprings suitable for our XE274HR cam, meaning they had both sufficient seat and open pressure, not to mention clearance for coil bind. We also took the liberty of checking retainer-to-seal clearance, but we had over 0.150 before contact. The one possible downside to the ported RHS heads was that the combustion chambers were slightly larger than the stock heads (65 cc vs 61 cc)  Holley Systemax Intake: 395...  Holley Systemax Intake: 395 hp at 6,200 rpm, 380 lb-ft at 5,000 rpm
While we had previously replaced the factory H.O. intake with the performance-oriented GT-40, we suspected the GT-40 was now limiting our combination. Leafing through the list of available upper and lower intakes for the 5.0L, we selected the Holley SysteMax combo. Though impressive in as-cast trim, we sent ours out to the good folks at Extrude Hone in Paramount, California, for some magic putty porting. The results were impressive, as the ported SysteMax intake and matching 75mm Holley throttle body improved the power output of the 302 combination dramatically. Where the previous combo with the GT-40 intake produced 354 hp and 378 lb-ft, the Holley manifold upped the peak numbers to 394 hp and 380 lb-ft of torque. The majority of the power gains came past 4,700 rpm, as the GT-40 offered more torque below that point.  Zex Wet EFI Kit (100 hp):...  Zex Wet EFI Kit (100 hp): 506 hp at 5,600 rpm, 547 lb-ft at 4,700 rpm
This is where the power gains started really getting serious. Nothing adds power as easily and inexpensively as nitrous oxide. Literally at the push of a button, it's possible to add 100 hp or more to just about any combination. For our test motor, we ran 100hp jetting in the Zex Wet EFI kit. The wet kit combined the nitrous and fuel into a single fogger, which we mounted in our air intake in front of the Holley throttle body. The Zex kit included everything needed to add as much as 125 hp to our injected 5.0L (more with optional jetting). The kit is unique in that it features an optional controller that is capable of learning the TPS voltage to ensure the system can't be activated unless the motor is running at wide open throttle. This is a nice safety feature, although it doesn't prevent the user from engaging the nitrous too early in the rpm range (something that will create havoc).  HP Performance Turbo Kit:...  HP Performance Turbo Kit: 622 hp at 5,800 rpm, 637 lb-ft at 4,700 rpm
The final modification applied to the 5.0L was a single-turbo kit from HP Performance in Roswell, New Mexico. The kit featured a 67mm turbo, an air-to-air intercooler, and 44mm wastegate. All of the exhaust tubing featured Jet Hot-coated to maximize heat energy to the turbo, while the intercooler was sized for maximum heat rejection. Look for this kit combined with a larger turbo on a 400-plus-inch stroker in the near future, but we have successfully run the system at over 1,000 hp, so it was more than sufficient for our mildly modified 302. Use of the nitrous and turbo kit is why we installed the forged crank, rods and pistons. The kit taxed the 36-lb/hr injectors on this application, so we manually raised the fuel pressure on the boost-referenced regulator to 60 psi (from 43 psi in NA trim). This provided plenty of fuel to keep the air/fuel mixture safely at 11.5:1.  Next we replaced the factory...  Next we replaced the factory intake with a FRPP GT-40. The GT-40 was run with an AccuFab 65mm throttle body, which was worth a few extra horsepower.  The GT-40 induction improved...  The GT-40 induction improved the power output from 261 hp and 321 lb-ft to 280 hp and 326 lb-ft. The gains were significant above 3,700 rpm, though the GT-40 lost out to the stock intake below 3,200 rpm.  Knowing the stock heads are...  Knowing the stock heads are restrictive, we replaced them with a set of RHP Pro Elite heads. The RHS heads offer aluminum construction, CNC-porting, and a host of other features.  We selected the smaller 205cc...  We selected the smaller 205cc Pro Elite heads. According to RHS, the 205cc intake ports flowed nearly 300 cfm-roughly double that of the stock heads....  ....The RHS Pro Elite heads...  ....The RHS Pro Elite heads featured a 2.05/1.60 valve package and 65cc (measured) combustion chambers. Compared to the stock heads (61cc), this dropped the static compression by roughly 0.4 points.  The Pro Elite heads were run...  The Pro Elite heads were run with 1.6-ratio, aluminum roller rockers from Comp. After re-installing the GT-40 intake on the RHS heads, we were rewarded with peak numbers of 354 hp and 378 lb-ft of torque, gains of 40 hp and 30 lb-ft over the stock heads (measured peak to peak).  Thinking the GT-40 was holding...  Thinking the GT-40 was holding back our combination, we replaced it with a Holley SysteMax. Run with the SysteMax upper and lower, and matching 75mm Holley throttle body (shown with turbo combination),....  ....the normally aspirated...  ....the normally aspirated 302 produced 394 hp and 380 lb-ft of torque. The ported Holley SysteMax lost out to the GT-40 below 4,700 rpm, but offered over 50 hp past 6,000 rpm.  The Zex Wet EFI nitrous kit...  The Zex Wet EFI nitrous kit features a single fogger nozzle to combine fuel and nitrous. We mounted the nozzle in a radiused air horn in front of the throttle body.  Engaging the nitrous all but...  Engaging the nitrous all but transformed our 302 into a stroker 408, as the chemical warfare upped the peak power numbers to 506 hp and 547 lb-ft.  The final modification involved...  The final modification involved the installation of a single-turbo kit from HP Performance. The kit featured an air-to-air intercooler, Tial wastegate, and this 67mm turbo capable of easily exceeding the power limitations of our production 302 block.  The final modification involved...  The final modification involved the installation of a single-turbo kit from HP Performance. The kit featured an air-to-air intercooler, Tial wastegate, and this 67mm turbo capable of easily exceeding the power limitations of our production 302 block.
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