Modified Mustangs & FordsHow To Engine
HOT ROD RESCUE: Solving Driveability Issues on a Blown Ford 5.0L EFI
Chris Travers has been into F-100 pickups a long time. Since purchasing his bright-orange 1956 model 20 years ago, it's been in what he says is a state of never-ending evolution: "I've upgraded everything except the paint." An Industrial Chassis Dodge Dakotabased independent front suspension with rack-and-pinion steering is used up front. Out back, a 3.55:1-geared C4 Corvette IRS from Flat Out Engineering gets the power to the ground.
For the last 10 years, that power has come from a Kenne Bell (KB) supercharged, 0.030-over 302 Ford Windsor with 8.5:1 pistons, a Ford Performance Parts (FPP) E303 hydraulic roller cam, rebuilt stock heads with a three-angle valve job, electronic fuel injection (EFI) managed by the versatile 1989 Mustang factory A9L electronic control unit (ECU), and BBK 19861993 Mustang headers (1-inch primaries into 2-inch collectors). Gear changes are via a Performance Automatic Ford 4R70W electronic automatic overdrive managed by a PCS Simple Shift standalone controller.
"At the time I built the motor," Travers says, "I tried to get the best advice from professionals and my fellow hot rodders. I wanted decent performance but also be able to cruise in town and on long-distance highway trips. I wanted a full set of creature comforts like air conditioning. What I ended up with was good full-throttle, top-end performance but not great driveability."
At best, that's an understatement: Travers explains that since the combo went together, "At idle and off-idle—especially when the engine is cold—there's been a constant surging cycle. I couldn't give it gas when it was cold; it would die out. After warm-up, it belched, misfired, and used gas. I had to break the tires loose to get it going. It didn't like to run under 1,800 to 2,000 rpm. It wasn't too happy in traffic. Once on the freeway, it was fine. With the overdrive and mild gears at 75 mph, it cruises at 2,200 rpm. If it was a carb with no supercharger, I could have fixed it!"
Alas, it wasn't. Travers just lived with the problem. He tried several dyno-tuning shops, different spark-plug heat ranges, messed with the ignition timing, had the ECU reprogrammed—all of which yielded only a mild improvement. "No one could really get the truck to idle." Then Travers read about other HOT ROD rescues undertaken by Ford expert Mark Sanchez at Advanced Engineering West (AEW). "He seemed really dialed in to solving problems with these EFI Ford engines, so I took the truck over to him. Mark is delightful! He's so anal about stuff, so into the little details needed to get things right."
Sanchez reports, "The vehicle drove in under its own power. In the driveway, the truck was already misbehaving. The idle was surging, going up and down; eventually, it would stall. When I put it in gear, it definitely stalled if you didn't give it some throttle while foot-braking it. It would stall when coming to a stop sign. The truck was a two-foot driver. From my experience, this indicated the motor was rich. I confirmed this by pulling the spark plugs. They were fuel-fouled.
"I examined the [fuel] injectors and saw they were 42-lb/hr units. There's no need to have an injector this size on a mostly stock, street-driven 302, even with a supercharger. I like to see the injector's duty cycle—the time it's open—in the 70- to 80-percent range. If it's less, at idle the injectors may open only 0.51 millisecond, too short for accurate ECU control. A too-small injector (more than 80-percent duty cycle) also introduces control issues and may not be capable of delivering sufficient top-end fuel.
"I could have made the injectors work with a properly calibrated MAF [mass airflow sensor], but from the way the truck was running, I could tell the existing MAF was not properly matched to the injectors. Additionally, the MAF was poorly mounted between a corrugated duct on one side and a right-angle elbow approaching the throttle-body on the other."
A] New air intake duct
B] New Pro-M MAF sensor and air filter
C] New 75mm Accufab throttle-body
D] 30-lb/hr fuel injectors, new intake gaskets
E] MSD 6-BTM boast/retard ignition box
F] Optional MSD HVC E-core 42,000-volt coil
G] Optional MSD Ford 5.0L EFI billet distributor
H] Replace fouled spark plugs
I] Check and fix rocker-arm/lifter preload
J] Change engine oil and filter
K] Replace engine coolant
The Fix: Fuel, Air, Spark
Travers' A9L ECU is very tolerant of engine mods. The "trick" for getting everything to play together is the MAF sensor. "It needs to be properly calibrated for the engine size, the fuel-injector size, the model year of the ECU, the throttle-body size, and even its relationship to the ducting and air cleaner," Sanchez explains. "MAF calibration involves changing the voltage the meter puts out in relationship to the amount of air flowing through it. If this is right for the combo, there's no need to recalibrate the Ford ECU. In my opinion, only Pro-M gets this right."
Pro-M MAFs are individually custom-calibrated for the specific combo, so before ordering the MAF, Sanchez had to decide on fuel-injector and throttle-body sizes. From experience, Sanchez knew street-driven, KB-supercharged 302 engines making moderate boost perform best with 30-pound injectors.
Unlike a carburetor, a properly designed EFI throttle-body is insensitive to a vacuum signal. "You can't go too big on a throttle-body," he insists, so although not mandatory for fixing Travers' immediate issue, Sanchez replaced the original 65mm throttle-body with Accufab's 75mm billet unit to fully realize the supercharger's potential.
After settling on throttle-body and injector sizing, and with the other engine parameters known, the custom Pro-M MAF could be ordered. The Pro-M sensor comes bolted to the air filter and must be mounted as a unit. As Sanchez deemed Travers' original duct layout inefficient anyway, he fabbed a new duct from aluminum tubing and hose connectors. The MAF and air filter now mount in the wheelwell, where they receive cold outside air. The configuration is not only more efficient but polished up it looks great, too!
On the spark side Sanchez installed an MSD 6-BTM ignition box, an HVC coil, and a Pro-Billet 5.0L EFI distributor. Sanchez considers the 6-BTM with its adjustable boost-retard a must for blown motors. While not strictly required at Travers' performance level, the MSD coil and distributor provide plenty of insurance if Travers ever decides to turn up the boost. New Motorcraft spark plugs one step colder than stock replaced Travers' fouled plugs. The gap was tightened from the stock 0.048 inch down to 0.032 so the spark won't blow out under boost.
Sanchez removed Travers' previous piggybacked "chip," reverting the ECU to the original Ford calibration. As predicted, there was no need for ECU mods. Sanchez even left the base timing at the stock 10 degrees. Running on 91 octane, at 5 psi, the engine was happiest with 1-degree ignition retard per pound of boost (for a total of 5 degrees retard).
The Fix: Lifter Preload
At this point, Sanchez says, "The car would sit there and idle. But the engine still didn't sound right to me. The idle wasn't as smooth as other cars running the same cam and supercharger. Now that I at least got the engine running more or less OK, I decided to fix an oil leak coming out of the lower intake manifold that Travers complained about.
"To replace the lower intake gaskets, I first had to remove the blower, the valve covers, and the upper intake. I then noticed Travers still was running factory nonadjustable rockers. After I finished replacing the lower gaskets, I figured I may as well check the rocker-arm preload. If it's wrong, that could be the reason the engine still wasn't idling as smoothly as it should."
Since the mid-1970s, small-block Fords have used nonadjustable valvetrains with bolt-down rocker arms that are simply tightened to a set 25 lb-ft torque value. But the lifter preload still needs to be right so all the valves open and close the same amount at the same time. You can get away with slightly different valve-stem lengths and valve-seat margin distances on independently adjustable, stud-mounted valvetrains like a small-block Chevy, but not on a Ford. Sadly, this is all too often overlooked by the average corner machine shop.
Milling the block and heads, installing different-thickness head gaskets, or camshaft base circle diameter differences can also throw off the preload, but (assuming the valve margins and stem heights are correct) the amount of change would be consistent for all the valves. In this case, when Sanchez checked the valve heights using a straight edge, they varied individually, indicating the problem was the valve job.
But were the valves too long or too short? Sanchez determines proper preload by checking each valve in turn on the cam's base circle using a two-step tightening procedure as shown in the photos. Common solutions to incorrect preload are custom pushrods with different individual lengths, using adjustable (but heavy and bulky) pushrods, or converting to an expensive fully adjustable valvetrain. Sanchez's expedient solution is to shim the rocker-arm pedestals on the too-long valves and mill the pedestals if the valves are too short. Both were required.
Cold start and cold idle are now fine. After warm-up, hot-idle quality is good and the truck no longer stalls in Drive or when coming to a complete stop. "You no longer have to use two feet to drive the car," Sanchez reports. On Westech Performance's chassis dyno, with 5 psi of boost, the 8.5:1 motor's output rose from 170 to 210 hp at the rear wheels.
Sanchez sums up, "Bigger is not necessarily better. With throttle-bodies, yes; with injectors, no. MAF calibration is a critical component that all too often is overlooked." On engines with nonadjustable valvetrains, all the valve-stem lengths must be the same height, meaning your machinist must carefully pay attention when grinding the valve stems and reconditioning the valve heads and seats.
Need Junk Fixed?
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Accel, a Holley Performance Brand; Bowling Green, KY; 866.464.6553; Holley.com/brands/accel/
Accufab Inc.; Ontario, CA; 909.930.1751; AccufabRacing.com
Advanced Engineering West (AEW); Mira Loma, CA; 626.222.4648; AEWperformance@aol.com
Amazon.com Inc.; Seattle, WA; 866.216.1072; Amazon.com
AutoZone Inc.; Memphis, TN; 800.AUTOZONE; AutoZone.com
Breeze (Norma Americas Distribution Services); Lake Orion, MI; 855.NORMA.2U; NormaAmericasDS.com/brand/breeze
Castrol (BP Lubricants USA Inc.); Lewiston, KY; 800.462.0835; Castrol.com
Flat Out Engineering; Orange, CA; 714.639.2623; FlatOut-Engineering.com
Ford Performance Parts (FPP); Dearborn, MI; tech: 800.367.3788 or 313.621.0771; PeformanceParts.Ford.com
Industrial Chassis Inc.; Phoenix, AZ; 866.553.8996 or 602.278.6800; IndustrialChassisInc.com
Kenne Bell (KB); Rancho Cucamonga, CA; 909.941.6646 (orders) or 909.941.0985 (tech); KenneBell.net
Motorcraft Parts; Dearborn, MI; 800.392.3673; Motorcraft.com
MSD Performance; El Paso, TX; 888.258.3835 (toll-free), 915.857.5200 (general), or 915.855.7123 (tech); MSDperformance.com
Performance Automatic; Frederick, MD; 240.439.4650; PerformanceAutomatic.com
Pickups Limited Orange County Chapter; Anaheim, CA; PickupsLimited.com
Powertrain Control Solutions LLC (PCS); Ashland, VA; 804.227.3023; PowertrainControlSolutions.com
Prestone Products Corp.; Danbury, CT; 888.269.0750; Prestone.com
RockAuto LLC; Madison, WI; RockAuto.com
Summit Racing Equipment; Akron, OH; 800.230.3030 (orders) or 330.630.0240 (tech); SummitRacing.com
Vibrant Performance; Mississauga, ON, Canada; 905.564.2808; VibrantPerformance.com
Westech Performance Group; Mira Loma, CA; 951.685.4767; WestechPerformance.com