5.0L HO / EFI 302 Swap

The Fox-body 5.0L HO (High Output) ran from 1982-1995 in the Mustang and is the donor of choice because cores are cheap and everywhere. The block is a 302 Windsor, so it bolts where any Bronco 302 already lives and mates to the same small-block Ford bellhousing pattern your existing transmission uses.

The HO is a hot-cammed, better-breathing version of the same 302 covered in the factory V8 guide. What to look for when shopping a donor:

• Compression: 8.3-8.4:1 on the 1982-1986 HO, 9.0:1 on 1987 and later. The later engines make more power and tolerate pump gas fine.
• Camshaft: 1985 and later are hydraulic roller blocks. A roller block is worth seeking out — it takes modern roller cams without a $400 conversion and does not have the flat-tappet break-in risk.
• Heads: E7TE castings on 1987-1993 are adequate. GT40 heads (1993 Cobra, 1996-1997 Explorer) and GT40P heads (1997-2001 Explorer and Mountaineer) flow considerably better. GT40P heads have a relocated spark plug angle and need GT40P-specific headers — fitting standard headers to P heads results in plug wires against the tubes.
• Rating: 225 hp / 300 lb-ft as delivered in a 1987-1993 Mustang. In a Bronco with a mild carb setup, expect 240-260 hp and 310+ lb-ft.

Balance weight. Every 302 from 1982 forward is 50 oz-in externally balanced; 1981 and earlier 302s are 28 oz-in. The flexplate or flywheel and the harmonic balancer both carry the counterweight, so an HO long block bolted to your old Bronco's 28 oz-in flexplate will vibrate badly and eventually crack something. Buy the matching 50 oz-in flexplate or flywheel and use the donor's balancer.

Firing order. The HO camshaft uses firing order 1-3-7-2-6-5-4-8, not the 1-5-4-2-6-3-7-8 of a standard 302. Wire the distributor cap to the HO order if you keep the HO cam. Installing a non-HO replacement cam flips you back to the standard order. Getting this wrong produces an engine that fires, runs terribly, and sends people chasing carburetor problems for a weekend.

Oil pan. The Fox-body Mustang pan is a rear-sump design; the early Bronco's front crossmember demands a front-sump truck pan with the matching pickup tube and dipstick. Swap the pan on the stand before the engine goes in the truck — discovering the clearance problem with the engine hanging on the hoist costs an afternoon.

For most early Broncos, carbureted is the path of least resistance and the one most owners should choose. Drop the HO long block onto the existing 302 mounts and add:

• Edelbrock Performer 289/302 dual-plane intake (~$260)
• Edelbrock Performer 600 cfm 4-bbl, #1405 manual choke or #1406 electric (~$400), or a 650 cfm #1477 for larger builds
• Hooker shorty headers into 2.5" dual exhaust (~$280 plus fabrication)
• Duraspark distributor, or a PerTronix Ignitor with an MSD 6AL box (~$210)
• Mechanical fuel pump feeding 5-7 psi — no return line or high-pressure plumbing required

That combination gives 240-260 hp with a street tune and good idle quality on the dual-plane manifold. Total parts, with a $900 core, land near $2,200-2,600. Set it up per the tune-up guide once it runs, and run a compression and leak-down test on the core before you spend a dollar on top-end parts.

If the donor is a 1988-1993 Mustang, you can keep the mass-air EFI rather than carbureting it. That means retaining the donor ECU, engine harness, MAF, injectors, and TFI distributor, then stripping the harness of A/C, emissions, and body branches until only the engine circuits remain. Plan 20-30 hours for a first-time harness cleanup, and budget for the supporting systems the carb build does not need:

• High-pressure fuel supply. EFI wants roughly 39 psi at the rail with a return line. That means an in-tank or frame-mounted high-pressure pump, a return line run, and usually a new sender — see the fuel tank and sending unit guide.
• Clean power and ground. The ECU needs a dedicated switched feed and solid grounds. A 50-year-old Bronco harness is not a good foundation; pair this with the wiring harness replacement.
• Accessory drive. Fox-body 5.0s are serpentine; the early Bronco is V-belt. Pick one system and source a complete matching bracket set rather than mixing.

The payoff is genuinely better cold starts, better fuel economy, and automatic altitude compensation — meaningful if you wheel above 6,000 feet. If a turn-key injected setup is the actual goal, weigh this against a purpose-built aftermarket EFI conversion, which is designed for retrofit rather than adapted from a car harness and often costs less in hours than it does in dollars.

• From an existing 302: motor mounts, bellhousing, and transmission carry over unchanged. This is the low-drama version of the swap.
• From the 170/200 I6: you need V8 motor mounts and frame stands, a V8 bellhousing for the T-18 or three-speed, a V8 radiator and shroud, V8 exhaust, and often a different driveshaft length. Add $600-1,000 and a weekend.
• Cooling. The early Bronco's cooling is marginal at stock power and more power makes more heat. Plan the radiator and fan upgrade into the same project rather than chasing overheating in July.
• Exhaust. Headers demand full exhaust fabrication behind them. A muffler shop will bend 2.5" duals for $350-500.

• Buy the core running if possible. A $900 engine you heard idle is worth more than a $500 unknown. Compression-test before purchase or immediately after.
• Check the roller lifter retainers on 1985+ blocks. Cores that sat outdoors rust the spider and dog bones.
• Do not reuse the old fuel line for EFI. Low-pressure rubber hose will fail under 39 psi, and the failure mode is fuel spraying onto a hot exhaust. Use proper submersible or PTFE-lined EFI hose with fuel injection clamps throughout.
• Verify hood and firewall clearance with the intake and air cleaner mocked up before final wiring. Tall aftermarket intakes fit a Mustang, not always a Bronco.

Why it works

• bolts onto existing 302 mounts with the stock bellhousing pattern
• cheap HO cores are widely available, and 1985+ blocks are roller-cam
• 240+ hp achievable with basic bolt-ons
• enormous aftermarket and forum support behind every step

Trade-offs

• EFI retention adds 20-30 hours of harness and fuel system work
• a carbureted build gives up cold-start and altitude advantages
• requires full exhaust fabrication once headers are fitted
• balance weight, firing order, and oil pan mistakes each cost a weekend to unwind

Tools required

• engine hoist
• load leveler
• floor jack
• complete socket set
• torque wrench
• multimeter
• fuel pressure gauge
• harmonic balancer puller
• engine stand
• compression tester

Parts

Sources

• 5.0 HO swap discussion — ClassicBroncos forums
• Fox-body 5.0L HO specifications
• Edelbrock Performer intake and carb application data

Related

• Factory 302 V8 — Specs, Carb, and Tune
• Factory 351 Windsor — Specs and Swap Value
• Carburetor to EFI Conversion
• All Ford Bronco guides & tools
• Browse the full DIY database

Written and maintained by an AZ wheeler and driveway wrencher. How we source guides. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.