Skip to main content
Engine Tech Advice Updated 7/16/2023 7:07:44 PM

Modern Engine Swaps into an Early Bronco

A common question we receive at TOMS OFFROAD is, “What are my options for modern engine setups?” followed by, “What parts do I need when doing these swaps?” To answer these questions, you will want to think about what setup you are currently working with and what you are hoping to achieve when the project is finished. Below we have given you multiple scenarios and some recommendations.


If you currently have a rebuilt motor or a strong running engine but would prefer to have EFI (electronic fuel injection), the easiest way to achieve this is to install an aftermarket throttle body injection kit such as the Holley Sniper kits we offer. The Holley Sniper EFI fuel injection system is the ideal throttle body style fuel injection conversion for your early Bronco. This EFI kit will bolt in place of your carburetor for a simple fuel injection conversion. Our kit includes the new fuel lines you will need as the Holley Sniper requires a return line for the unused fuel. You will also need a high pressure fuel pump setup. The best way to achieve this is by adding a TOMS OFFROAD High Capacity 23 gallon Fuel Tank for EFI Conversions (part #6199). This fuel tank assembly includes the in-tank fuel pump necessary to run the Holley Sniper EFI kit. The Holley Sniper EFI units support 289, 302 or 351W engines from 250 HP to 600 HP. The Holley Sniper units come in polished or black and include a handheld tuner module. This is a self learning unit and supports timing control (with 2 wire alternator setups). Wide band O2 sensors need to be added to the exhaust system so the Sniper can read how much O2 remains in the exhaust as it exits the engine. This can be done by welding O2 bungs into your exhaust manifolds, headers or exhaust pipes. It is best to install the O2 sensors as close to the collector point as practical in order to get the most accurate readings. Monitoring O2 levels in the exhaust is a way of gauging the fuel/air mixture. It tells the computer if the fuel mixture is burning rich (less oxygen) or lean (more oxygen).


If you want to swap in a complete engine and transmission EFI fuel injection setup and don’t want to break the bank, then a 1989-1993 Ford 5.0L HO motor is a great option. The 1989-1993 Ford 5.0L HO motors are full roller motors (roller cam and lifters plus roller tipped rockers) and have mass air sensors (determines the mass flow rate of air entering the engine). From the factory the Ford 5.0 HO had 220 horse power. With a cam swap, valve springs and better air intake you can easily gain about 40 horsepower on top of that. Some modifications such as new heads or stroker kits, larger injectors, etc. will require the computer to be reprogrammed to the new parameters. One advantage of the Ford 5.0L HO motors is that they have the same motor mount location and bell housing bolt pattern as the factory 289 & 302 V8 engines found on early Broncos. However, they are 50 oz externally balanced unlike the pre-80’s 302 that was 28 oz externally balanced. This means you will need the correct 50oz harmonic balancer and 50 oz flywheel for manual applications or 50 oz flex plate for automatic applications. These motors can be found in Ford Mustangs and often come with an AOD transmission as well. When sourcing this power plant you want to get the entire engine along with the ECU/ECM (computer). The serpentine setup that comes factory on these motors will not work with a mechanical fan and in most situations it is easiest to swap out the serpentine setup for a factory v-belt drive unit using the following part numbers:

By swapping to this setup you are able to retain your standard radiator as opposed to converting to a reverse outlet radiator which is required with the factory 5.0 water pump. O2 sensors will once again be required for this setup. You will also need a high pressure fuel pump and a fuel tank with a provision for return line. Our #6199 EFI 23 gallon Fuel Tank works great. For the wiring, TOMS OFFROAD offers a complete plug and play 5.0 EFI wiring harness #6138. This 5.0 EFI Fuel Injection Wiring Harness is high quality and easily installed in your early Bronco. Designed to work with 89-93 Ford Mustang 5.0L EFI motors with mass air-flow, simply lay this kit over the engine and connect the wires. This harness will also work with 86-89 speed density Mustang engines. To run this EFI wiring harness on a 1986-89 speed density Ford 5.0L engine, you will need to ensure the MAP sensor is hooked up to vacuum and ignore the MAF sensor (it can be used for a future upgrade). This engine wiring harness is designed for engines that have the throttle body coming out on the passenger side of the upper plenum. A single connection into a power wire from the main wiring harness and it is done. If you are a skilled individual, you can strip the factory harness that comes with the Ford 5.0L motor and remove all unnecessary wires and re-loom the harness to save some money. 86-89 Ford 5.0L engines can be used, but they are slightly less desirable than the 89-93 version because they may not be roller motors and the speed density unit is not as efficient as mass air. For Bronco hood clearance, a car style 5.0L is necessary. Truck engine models have a much taller intake and will not fit without hood scoops and/or a 3″ body lift.


Another common swap is the late 90’s to early 2000’s Ford Explorer 5.0L engine. This is a desirable swap because you are able to use the factory serpentine set up. The Explorer motor is a very similar swap to the early 90’s Ford 5.0L with a few exceptions. Depending on the year, the Explorer motor can have GT40 or GT40P heads. The GT40P heads can lead to issues when purchasing headers due to the spark plug orientation. GT40 heads are great factory heads with good flow and increase the horsepower rating as compared to earlier Ford 5.0L engines. The Explorer motors vary year to year on wiring. Some are coil pack while others are standard coil. Also the mid-year 1999 and newer motors have a returnless fuel system. When purchasing a stand alone harness for this swap Ron Francis Wiring will build a harness for your specific application if you give them the specs on the motor you are planning on using. Later model Ford Explorer motors have an ECM/ECU that can be locked when pulled from vehicle and will need to be flashed, as of the date of this article Ron Francis does this as well. You would need a reverse outlet radiator to match the reverse rotation water pump. This engine also has the same motor mount location and bell housing configuration as factory making installation easier. However this is a 50 oz externally balanced engine like the early 90’s 5.0L so you will need the correct 50 oz flywheel for manual applications or 50 oz flex plate for automatic applications. These Ford Explorers usually have a 4R70W transmission that can be controlled by the factory ECU/ECM if the Explorer had an automatic transmission from the factory. This saves some money since a stand alone transmission control is not needed. The main benefit for choosing an Explorer motor over earlier 5.0L engines is the serpentine setup, otherwise the earlier 5.0L is an easier swap.


The final option we will discuss in this article is the new Ford 5.0L Coyote motor. This swap is becoming more popular by the day and is a great high end conversion that offers 420+ horsepower and increases the value of the Bronco exponentially. The early Bronco Coyote engine swap is considerably more expensive than the previous options but gives you a complete new powertrain. When doing a Coyote swap in your 66-77 Ford Bronco, expect to pay between $10k to $15k on parts alone at a minimum. This swap is also considerably more labor intensive. You can source a 2011-present Coyote 5.0L motor used or buy a new crate Coyote 5.0L engine from Ford Racing. You will also need a lot of parts from TOMS OFFROAD including custom motor mounts, headers, front drive bracket, miscellaneous bolt kits, powers steering spacer plate, O2 sensors, high pressure fuel system and more. Ford Racing sells a control pack for specific year breaks of the Coyote motor that is a stand alone harness for the engine. The Coyote 5.0 has a modular bell housing bolt pattern so a 4R70W or 6R80 automatic transmission are the most commonly used transmissions in these swaps. Either transmission requires a stand alone transmission controller. This swap seems to be the wave of the future but anyone looking to approach this conversion should take into consideration the costs and time involved before attempting it.


Any of these swaps are a great upgrade for your tired old early Ford Bronco power plant. Which is best for you really depends on what you are trying to achieve in your build. We recommend determining your end goal with this swap, how much labor you are okay with doing and what you believe you are capable of tackling. Once you have decided on an engine swap for your early Bronco, make a parts list with prices to determine if the final cost is within your budget. With any swap there are typically miscellaneous expenses that can arise, so be sure to include some miscellaneous extra in your budget calculation ($500 is generally a good number depending on your math and planning skills). With most applications we recommend also upgrading the cooling system at the same time to ensure your new motor is running at optimal temperatures. Also keep in mind that most EFI Motors are slightly taller and may require a body lift under certain circumstances. If you have any further questions please call and talk to one of our knowledgeable technicians.

More Ways To Get Help & Learn More

Get In Touch
Don't ever hesitate to contact us if you have any questions about a product or instructions. We're always happy to help!
(541) 779-1339
Check Us Out On YouTube
Subscribe to our Tech Tips channel for even more how-to's and help!
Visit our blog
Everything a Bronco enthusiast could want, from community announcements and event roundups to Team Roaming Wolves updates and contests!