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A worn-out full-size Bronco EFI 302 gets a new lease on life

Posted in How To: Engine on December 27, 2016
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Photographers: Bruce Smith

It looked like a sweet deal: A ’91 Eddie Bauer Bronco for $1,500. Ford’s full-size SUVs of that era were cool, with a lot of elbow room up front, a ton of space in back when the second-row bench is flipped up, they can tow 7,700 pounds, and have a very comfortable ride on and off-road. We had to check it out.

The owner said unforeseen financial burdens had forced him to part with the 25-year-old Bronco he’d bought a year earlier in hopes of making it a reliable and presentable daily driver. The truck looked decent from 50-feet, but up close you could see it’d been neglected over the years. Still, the engine ran, the body was straight, the interior intact but dirty, and it was a driver. A deal was made.

As with most budget-minded off-roaders who buy a “classic” 4x4, our initial end goal was to fix it up enough over time to be a reliable get-around work truck and dependable weekend backwoods exploration rig. This one looked like it’d fill those very goals once we addressed the typical mechanical and aesthetic pitfalls of a rig that wasn’t very well taken care of in the last decade.

Our classic SUV’s odometer showed 4,754 miles, which we were told was more than likely on the third lap around the counter. So we knew the engine and automatic were close to being on their last legs. But our hope was they’d hold together until next summer, at which time we’d address rebuild or replacement options.

Days after our 130-mile drive home we changed the engine oil and pried off the oil filter. Neither looked like they’d been touched in years, which went right along with how the filthy engine compartment looked. The brakes were overhauled and the 5.0L given a quick backyard plug-and-timing tune-up.

Then we installed a Pro Comp four-inch long-travel lift and Pro Comp A/T Sport 33s, along with adding a JB Custom Fabrication winch bumper with a Warn VR-10S winch so we could enjoy some winter wheeling. We were ready to roll. Our bargain buy was panning out better than we’d planned.

Eddie-The-Bronco on the trail just prior to the engine and transmission going south.

Decision time

But our joy was short-lived. A month and about 500 highway miles after the suspension was installed a persistent little oil drip from the front of the engine suddenly turned into a full-blown dribble. Two weeks after we’d replaced the timing chain and cracked timing cover, a messy, testy job in itself, Eddie-The-Bronco’s transmission started to slip between Second and Third while we were out exploring. Not good. Not good at all.

It was around that same time we started hearing a little rattle deep in the engine when it was cold, followed soon after by lack of oil pressure anytime the rpm dropped below 1,500. (Maybe changing the oil wasn’t a good idea afterall?) Neither engine nor transmission were going to make it to summer let alone through the winter. It was decision-making time.

We contemplated walking away from Eddie as fast as we could. But then had a change of heart and decided to bite the monetary bullet sooner than anticipated and invest in making it the dependable, respectable work/trail rig we originally envisioned. The time table of our anticipated year-long backyard refurbish 4x4 project truck just got moved to the front burner.

Our goal remained the same as it was the day we bought Eddie: Minimize the expenses as much as we can while bringing our old horse back to being a respectable, clean looking daily driver and weekend off-roader. Over the next few months we’ll give Eddie a new lease on life. First we’ll address the engine issue, then the transmission, followed by taking care of the cancer eating away along the wheel well lips, and then give the interior a makeover.

A driveway is the start of a new beginning for this ’91 Ford Bronco we affectionelty call Eddie-The-Bronco.

A helping hand

Unlike many magazine project rigs, Eddie-The-Bronco isn’t headed to a fancy shop with hoists and plenty of working space. Its home for most of this work is going to be done in and around the typical two-car residential garage. A cherry picker, air compressor, good selection of hand tools, fair weather, and at least one good friend with mechanical skills will become invaluable to the success of our goal.

Eric Sampayo is one such friend. The owner of Monroe Auto Repair (Eugene, OR), Eric offered his expertise and the driveway of his house to undertake the engine and transmission work. We did most of the work outdoors, using his garage as our temporary parts storage area and workshop when the Pacific Northwest rains rolled through. It was fun and brought a lot of fond memories from back in the day when we were teenagers just starting out working on our first 4x4s.

Pulling out the 5.0L EFI V-8, which was the standard engine in the Eddie Bauer Broncos of the time, was easy once we dug through, labeled and set aside the mass of ‘90’s smog equipment piled on the Ford small-block. We also dropped out the T-case and E4OD automatic.

The nice thing about Ford trucks of that era is they have a lot of room in the engine bay, so it’s easy to pile all the smog-related hoses, electrical wiring and tubes to the sides and lift out our oil-and-dirt-encrusted 302 without touching the radiator.

One of the nice aspects of rebuilding the engines of older 4x4s such as the full-size Broncos is they had a lot of room under the hood, making it easy to pull out the V8 without removing the radiator or grille.

Little 302 warm-up

With the old 302 Windsor sitting on the garage floor, we considered replacing it with a 351W from the same era. Then we regained our senses. We didn’t want to deal with changing the computer or worrying about all the smog-related hoops required by our state’s smog laws if we made such a change. We wanted to keep this part of the Bronco’s upgrade relatively simple.

In addition, neither of Ford’s early truck EFI V8s were powerhouses. The 5.0L 302 eked out 185 hp at 3,800 and 270 lb-ft at 2,400 rpm. The 351 wasn’t that much stouter, making 210 hp at 3,800 rpm and 315 at 2,800 rpm. With a mild cam, better intake, headers and freer-flowing exhaust, a warmed-up long-block 302 would make more power than its bigger brother.

Finding a rebuilt Ford truck Vin “N” EFI 302 is easy. They are plentiful, which means rebuilt ones can sometimes be picked up for a bargain depending on where you live. We bought our .020”-over rebuilt long-block from a local engine machine shop for $1,400, which included the cost to swap out the stock flat-tappet hydraulic cam and rail-type rockers for a mild-lift hydraulic roller-cam valvetrain we’d sourced from Comp Cams. The swap necessitated drilling out the stock Ford SBF rocker pedestals and the installation of Chevy-style screw-in studs to accept Comp Cam’s 1.6-ratio roller-tip rockers with adjustable locking nuts. Then they swapped out the stock valve springs for the higher-rate Comp Cams valve springs that came with the roller-style cam and roller lifters, installed the “dog bones,” valley retainer, and adjusted everything to spec using new stock Ford OEM pushrods.

We could have stayed with the 5.0’s flat-tappet hydraulic cam, but opted instead to change it out for an Xtreme Energy roller-style cam, lifters, springs and timing gear set from Comp Cams for better all around performance and efficiency.

Cam considerations

The roller-type Xtreme Energy (PN 31-000-8) cam we choose was a custom ground version of Comp Cam’s popular 35-512-8 run in 351s, a recommendation of Comp Cam’s Jeff Peritore.

Our goal was to spend a little extra for a roller cam setup that would give us the best performance gains within the constrictions of the speed-density (SD) EFI system used on the ’93-older EFI truck 302s. (The later F-150/250/Bronco 5.0s with Mass-Air can run much more aggressive cam profiles.)

“Our 31-000-8 Xtreme Enegry cam with the duration at .050 of 206/212 and .481 intake/exhaust lift and grind of the 351 35-512-8 will provide more air and a wider torque curve down in the lower RPM where 4x4s like yours need it,” Jeff said. “The only difference between the two cams is we grind the 351 version to fit the 302 firing order to work those older Ford 302 ECUs.

He also told us this particular Extreme Energy cam pairs nicely with a E4OD equipped with an 1,800-2,200rpm torque converter such a TCI’s Saturday Night Special. “The torque converter’s 400-500rpm bump above the stock version would help maximize your engine’s power curve for off-road use and towing applications,” Jeff said.

We followed Jeff’s recommendations during the engine re-assembly. We nixed the stock EFI intake for an Edelbrock truck EFI intake and plenum, and bolted on a BBK 61mm Power Plus throttle body to replace the stock 56mm TTB. Edelbrock and BBK techs we consulted with say that combination should add close to 40hp to our engine, and significantly improve low- to mid-range throttle response.

During disassembly we found that both of Eddie’s cast iron exhaust manifolds were cracked, which is a common malady of the early truck 5.0s. We also surmised the “Y”-pipe/catalytic converter hadn’t been touched since our old horse rolled off the assembly line at Ford Truck’s plant in Wayne, Michigan. So we replaced the upper exhaust with a set of JBA stainless “shorty” headers and a Magnaflow Y-pipe with built-in, performance-style catalytic converter.

Upgrading to a roller-type cam in the Ford truck 302 requires replacing the 5/16” bolts that hold the rail-type rockers to the pedestals with 7/16” Chevy-style screw-in studs. An engine machine shop will have to do that work, drilling and tapping the heads accordingly.

Screamin’-hot spark

While getting our rebuilt long-block ready for its transplant into Eddie we also dumped the stock distributor, coil and and cheap plug wires for Performance Distributors’ Hot-Forged 5.0L distributor, LiveWire plug wires and Screamin’ Demon coil. You can’t have too much juice heading to the plugs!

Our truck’s distributor was worn out, so replacing it was a must. Performance Distributors’ Hot Forged distributor is machined using computerized CNC mills and lathes to create exact tolerances, which plays a big role in how the juice is delivered to the plugs. It also contains PD’s high-dwell Dyna-Module for increased spark duration, which provides better throttle response and more low-end power over the stock Ford ignition system.

PD claims the 45,000-volt Screamin Demon coil and LiveWire plug wires provide the ultimate in delivering the hottest spark possible to the plugs without interference to any electronics or sound system that we might run in the future. Using these ignition enhancers allows us to now gap the plugs to .060” to further maximize our little 302’s fuel burn, which we hope leads to more power and better fuel economy.

The next phase

A half-hour with a pressure washer sipping Purple Power cleaner and the engine bay was ready to accept our shiny new rebuilt-and-warmed-up SBF. Our 5.0L isn’t a race engine by any means, nor is it meant to be.

The upgrades we did to the remanufacturerd long-block – intake, valvetrain, ignition and exhaust – were done to make it a more reliable, efficient, stronger performing replacement for what was under the hood a month ago.

Our next focus on getting Eddie-The-Bronco back on the road will be tearing down the smelly E4OD automatic and warming it up to Super Duty level so all of those new ponies are pulling their hardest when reaching the tires. We’d already dropped the trans for the engine rebuild, so now it’s laying on the garage floor waiting its turn to begin a new life under our old Bronco. Stay tuned!

We used BG’s Pre-Lube during engine re-assembly to make sure the cam, lifters, and roller-tip rockers would be well-lubricated on first start-up. Note: During oil changes Comp Cams requires a special zinc oil additive be used with their roller cams.
Comp Cams’ roller-type Xtreme Energy (#31-000-8) cam we choose was a custom ground version of Comp Cam’s popular 35-512-8 run in 351s. The new cam has a .481” lift, giving our truck’s 5.0L a wider, stronger torque curve at lower rpm than the factory flat-tappet cam.
Our engine’s 1.6-ratio roller-tip Comp Cams rockers are the budget upgrade are more efficienctthan the rail-type rockers found in the late ‘80s through late ‘90s Ford truck V8s. Upgrade requires installing studs with adjustable rocker nuts to achieve proper pushrod adjustment.
Hydraulic roller lifters are taller than their stock flat-tappet counterparts, so they require “dog bone” retainers as guides. A special spring-pressure plate bolts into the galley to hold the ‘bones in place.
Eric Sampayo spent several days helping us removing Eddie-The-Bronco’s engine and replacing it with a fresh long-block. Even more time was spent cleaning up the old brackets, valve covers, and accessory parts so we could save money on our budget rebuild.
We only splurged on a few performance parts on the rebuild including this Performance Distributor Hot-Forged 5.0L distributor, plug wires and Screamin’ Demon coil. Hotter spark, better performance.
Ford trucks have big engine bays making it easy to drop in a rebuilt engine using a cherry pikcer. The E4OD automatic was also pulled out to be rebuilt, giving plenty of room to drop in our new powerplant. This is also good time to clean the engine compartment.
Our “new” 302 will be buried in smog hoses, tubes and wiring to stay EPA-compliant for our needs. We anticipate it’ll still be making at least a third more ponies than the worn-out one it’s replacing while pulling stronger and being more fuel-effcient than a 351.
We swapped out the factory EFI intake and plenum for this Edelbrock Truck 5.0L EFI system. The longer runners and ported manifolds flow a lot more air than the factory did, giving our little 302 an expected bump of 30-35hp.
BBK’s twin 61mm-bore throttle body is a nice upgrade for truck 5.0Ls. It’s a perfect companion with the Edelbrock EFI intake, and should give our engine another 10-15hp on top of what the new intake provides. The CNC machine work is first-class, too.
The Xtreme Energy 31-000-8 cam is a duplicate version of Comp Cam’s popular 35-512-8 many off-roaders put in 4x4s running 351s. The lift and duration is maximized for use with Ford EFI V8s that use speed-density computer algorithms prior to the switch to the mass-air-flow system in 1994.
With the warmed-up reman engine back in place, all that was left for use to do before cranking it up was to plug in the Performance Distributor’s LiveWire plugs wires and do the normal engine break-in procedures.

Sources

TCI Automotive
Ashland, MS 38603
888-776-9824
www.tciauto.com
Comp Cams
Memphis, TN 38118
901-795-2400
http://www.compcams.com
Performance Distributors
Memphis, TN 38132
901-396-5782
www.performancedistributors.com
BBK Performance
Temecula, CA 92590
951-296-1771
www.bbkperformance.com
MaganaFlow Performance Exhaust
Rancho Santa Margarita, CA 92688
800-990-0905
www.magnaflow.com
Edelbrock
Torrance, CA 90503
800-416-8628
www.edelbrock.com
BG Products, Inc.
800-961-6228
www.bgprod.com

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