Until the late ’80s the concept of fuel injection was something that had many of us running scared. In North America, Ford first brought us into the modern age, introducing its sequential fuelie setup on performance vehicles in the mid-’80s, beginning with the 2.3-liter four-cylinder Turbo engine, found in the 1983½ Thunderbird Turbo Coupe and Mustang GT Turbo, followed shortly after by the hallowed ’84 SVO. For 1986, it added it to the venerable 302 V8, but it would take time for traditional hot rodders to embrace this new fangled technology and indeed for a few years, car guys and gals would tear off these EFI systems and replace them with carburetors. However, today, it’s almost impossible to find a new vehicle that comes with a carburetor. Fuel injection has proved itself to be more reliable and efficient, promoting far better starting, in both cold and hot weather, delivering reduced fuel consumption, with better atomization for more power, improved throttle response and lower exhaust emissions than were ever possible with a carb. And it’s probably just as well, considering how stringent federally mandated emissions (and now fuel economy) targets have become for new vehicle manufacturers. But as good as all that stuff is, our business is primarily about classic cars, because they’re far more interesting. So let’s get back to those.
WHY FUEL INJECTION?
Before you begin this project, you need to figure out why you’re doing it. The primary objective of choosing fuel injection is to make the car drive better, but it does have some drawbacks. If you own a particularly desirable classic Ford, then modifying it to use EFI, whether the car is complete or not, will likely hurt its long term value. So, for cars, like a Mustang Boss 302, Mach 1, GT Cobra Jet, it’s best to stick with what the factory offered, since A; the car isn’t likely to be a regular driver and B; converting it to fuel injection, can scare buyers away, since folks looking for these types of cars nearly always want original or correctly restored examples.
However, if you own one of the plain-Jane classic Fords that were built in huge numbers between the ’60s and ’80s then, anything from a 1965 Mustang coupe, to a 1970 convertible or even a monster barge like a 1978 Ford LTD, is fair game for EFI. For cars like these, the benefits of fuel injection far outweigh the drawbacks. It’s especially true on the mid- to late-’70s cars that found it a struggle to breathe and run, thanks to lean mixtures and retarded ignitions, along with their tiny two-barrel carburetors and narrow exhaust systems. Think about how slow and rough running these cars are in factory trim compared with their successors that came along 5 to 10 years later. Many of the later models still sported the same basic engines, but separating the air and fuel paths, plus squirting the juice directly into each cylinder and using an electronic brain to regulate fuel flow, did wonders for 20-year-old engines and gave birth to a second performance revolution. The combination of sequential fuel injection and the 302 V8 created for Ford fans, their answer to the small-block Chevy. It was exceedingly easy to coax more power out of these little mills, while maintaining a level of driveability and fuel economy not possible with a carburetor. That performance revolution continues to this day and the number of speed parts now available for the fuel-injected small-block Ford V8 is simply staggering, a major reason why more and more older Fords are receiving fuel-injected powerplants.
The question here, is, do you start with a donor car or buy yourself a complete system from an aftermarket manufacturer. There are pros and cons with both. If you’re on a budget, this can seem like the most attractive route. For a classic Mustang or Ford, your best bet is to find a car that came with Ford’s Electronic Engine Control (EEC-IV) processor. That means 1986-1993 Mustang V8s, 1987-1993 Thunderbirds and Cougars, 1986-1992 Lincoln MK VIIs and 1986 Mercury Capri V8s. The reason being is that the EEC-IV is simple and extremely forgiving, you can make all kinds of adjustments to your engine, from changing the camshaft to installing a supercharger or nitrous kit and the system can be easily adapted to compensate. However, if you do go this route, you should stick to a single donor vehicle and use the complete EEC-IV system from it, that includes the main fuel injection wiring harness, Ford A9L computer, fuel rails, fuel injectors, fuel pump and the sensors required for the system to operate, the Manifold Absolute Pressure Sensor, Inlet Air Temperature Sensor, Throttle Position Sensor, Oxygen sensors, water temperature sensors, plus, if the car uses Mass Air metering, the Mass Air hot wire sensor. These sensors monitor the flow of air and fuel and exhaust gas as well as their respective temperatures. Without their input, the computer is not able to accurately consult its look-up tables, which tell it to deliver the right amount of air and fuel into the engine’s combustion chambers. If you’ve seen an EFI car that’s running rough, it’s largely due to faulty or dirty sensors which are hampering the computer’s ability to measure and record its various parameters and therefore not make accurate adjustments to the air/fuel ratio.
When considering this swap, you’ll also need to bear in mind that SEFI systems require much higher fuel pressures than carbureted cars (around 45 psi versus 8-9 psi) so you’ll also need to use a fuel pressure regulator and a high flow electric fuel pump that are up to the task.
To gain insight into what exactly is involved, we talked to noted Mustang builder and former NMRA World Champion drag racer Joe Da Silva, who has performed some 100 carburetor-to-fuel injection conversions on Fords over the years. We figured that if there was anybody who knew about this stuff, it was Joe.
“When it comes to converting over to fuel injection, there’s more to it than just ripping off a carburetor and installing fuel rails and a new manifold. You also have to take into consideration the engine’s firing order and camshaft. On Fords, the 302 H.O. motors use a 1-3 firing order, whereas many older engines use a 1-5. So the harness for these engines works on the 1-3 principle. You’ll also need to change your camshaft. Cams for carbureted engines are designed to ramp in a lot of air from the top of the manifold and into the engine so the carb can deliver the required amount of fuel. This means that a lot of carbureted camshafts feature narrow lobes and low lift. Because this high level of airflow into the top of the engine isn’t needed on sequential fuel injected motors, they use cams with much greater lobe separation and higher lift. In conjunction with specifically designed heads and intake manifolds on EFI engines, this promotes greater airflow inside the plenum and ports, which increases power and torque on fuel-injected cars. For many fuel-injected conversions, it’s best to get yourself a custom ground camshaft since each engine is slightly different and you want to be able to maximize power and driveability. A good camshaft company or engine builder should be able to help you select the right cam based on your objectives.”
When it comes to finding the right harness, Joe also has a few words of advice. “From my experience, the best harnesses are the 1987-1993 Mustang units, because they’re very adaptable, but if you’re doing this conversion and are planning more modifications down the road, you’ll need to use a Mass Air Flow sensor, found on the 1988 California Mustangs and all 1989-1993 Mustangs. The 1987 and 1988 non-California cars use speed density metering in which the computer ‘assumes’ the right airflow and adds the required amount of fuel, based on input from the Manifold Absolute Pressure sensor and intake air temperature sensor. It’s not very accurate and the computer is not able to adapt to major changes in airflow, which causes erratic idling and other driveability issues if you decide to modify the engine down the road, like changing the camshaft or adding a blower. MAF systems on the other hand are far more adaptable because the hot wire sensor is able to precisely measure airflow to the computer, which can then make adjustments to the air/fuel ratio to compensate. You also need to make sure you get the right year of computer that corresponds with the harness, a major reason why you should grab a complete EFI system from a single donor car. If you start mixing and matching you’ll be forever chasing your tail trying to track down faulty wiring, because the car just won’t run right.”
A big part of your EFI plans concern the fuel system. We’ve already touched upon the high pressures required, but if you are using an EEC-IV based setup you’ll need to factor in a forward feed and return line for the fuel system, since the electric fuel pump, pushes fuel down the feed line to the rails, while any unused gas is returned straight to the tank. Because carbureted cars do not use a return line, you’ll need to install one, in fact the best option is to plumb for a new feed and return, since you’ll want lines that are designed to support sequentially fuel injected systems for best results. As for the pump itself, Joe has a couple of suggestions. “I’m actually a big fan of externally mounted booster pumps on EFI conversions, that way you can wire in a high flow pump on the chassis, I’ve had much success with Vortech Engineering’s T-Rex kits which come with everything you need including, wiring and mounting brackets. That said, an internal, in-tank pump, like those used on 1986-present Mustangs is a good idea, because the pump is also cooled by the fuel in the tank. But on an older Mustang or Ford, you’ll need to have a gas tank specifically designed to use an in-tank pump since they did not come with them in the first place – and don’t even think about modifying your existing fuel tank.”
Injector size is one thing that’s talked about a lot, but many people go for too large an injector. If you’re doing this conversion on an early Mustang or ’60s – early ’70s Ford that will be a regular driver, with a mild engine, the standard 5-liter Mustang’s 19 lb-hr injectors will work just fine. There is actually a way of calculating which size of injectors you should use in relation to your engine’s power output (see sidebar). Mustangs and other fuel injected Fords from the mid-’80s through the mid-’90s used Bosch EV-1 injectors, which are readily available and identified by their wide body and two pin attachments.
One other aspect you can’t forget is the car’s ignition system. On Ford EEC-IV equipped vehicles the TFI (or Thick Film Ignition) is standard equipment and identified by its wide distributor cap. These Motorcraft units feature extremely durable shafts and pickups, but there is one item that you need to consider and that can go bad – the TFI module. Mounted on the shaft, it regulates spark to the distributor from the coil, mounted on the driver’s side inner fender. Because of its location it is susceptible to heat, which can cause it to fail. Ford attempted to combat the problem by placing a rubber boot over the distributor, but using any form of heat shielding will help reduce the problem. If the TFI module on your donor distributor has gone bad, the car won’t start, period. Ford issued a recall on these units, so make sure you find one that has been replaced for your EFI project.
Another option today, if you can stretch your budget, is going with a complete aftermarket fuelie system for your classic Ford vehicle. For small block Fords, FAST (Fuel Air Spark Technologies) markets its XFI kit, that includes a whole host of goodies, including a specific intake manifold, fuel rails, injectors, control module (computer), throttle body, oxygen sensor and fuel injection wiring harness with OEM style connectors, an accurate and supremely adjustable Dual-Sync distributor and high-flow fuel pump. It retails for approximately $4,750, comes with complete instructions and can be used; not only on 302 and 351 Windsor based small blocks, but also mid-block 351C/351M and even FE 390/428-ci big blocks. However, do bear in mind that this kit is primarily designed for higher horsepower modified engines (it uses a single plane Edelbrock intake manifold and big-bore throttle body called the “Big Mouth,” designed to maximize airflow at higher rpm), though as a complete kit, its combination of quality parts and ease of installation
You love the looks and style of this…
…but want the driveability, fuel economy and reliability of this. Well there is a way and it’s called converting to electronic fuel injection using Ford’s proven EEC-IV based EFI system.
The veteran 289, 302 and even 351 Windsor small blocks, found in a huge number of classic Ford vehicles, are simple and durable engines, but the factory two- and four-barrel Autolite carbs often leave a lot to be desired, especially when it comes to starting and fuel economy, plus they don’t like cold or hot temperatures.
One of the best sources for obtaining fuel injection hardware on the cheap is to get your hands on a completed 302 H.O. engine, fuel injected wiring harness and computer, as found in 1987-1993 Mustangs. This one was installed in a 1989, which also means that it has a Mass Air Flow sensor, a considerable asset if you decided on big modifications down the road.
Separating the air and fuel paths did wonders for improving power and efficiency. This is a factory upper intake from a late ’80s 302 H.O. engine. It features fairly long intake runners, designed to maximize torque. Its purpose is to simply funnel air into the combustion chambers, unlike carbureted or throttle-body manifolds.
Here you can see the underside of the upper intake. Notice how the runners are in line with each other. A great way to improve power is to port the runners on both the upper and lower intakes, to improve airflow and increase power. Some aftermarket units, notably the Ford Racing Cobra feature cylindrical ports that are offset, designed to deliver greater and a more even flow of air.
Here you can see the lower intake of a 302 H.O. It is here where the air and fuel mix on these engines and also where porting can make the most impact.
Among other things, the 302 H.O. came with very sturdy distributors and exhaust headers straight from the factory. To this day they remain one of the most popular and affordable engine swaps for older Ford vehicles.
When you’re using a later-model donor car for your EFI conversion, you want to make sure you use the complete harness, sensors and fuel injectors that come with it, to minimize installation and driveability problems.
If you are planning on adding EFI to an existing engine, you will need to select the right size fuel injectors in order to avoid issues such as poor idling, rough running and possibly even detonation or too rich a mixture.
If you aren’t using brand new injectors, you’ll also need to inspect them for signs of cracks and also clogging, especially if the donor car has sat for a long period of time or its engine, while functioning hasn’t received a tune-up in a long time.
Another consideration when converting to EFI is the fuel tank. Later model Fords feature a high-pressure electric fuel pump mounted inside the tank. If you are installing EFI on a classic Ford then you need to consider getting a new tank that has provision for an in-tank pump that will fit in your existing vehicle, or choose an externally mounted pump.
Because sequential electronic fuel systems run under very high pressure, (around 45 psi) it’s a good idea to install a cut-off, in case of an accident. Fox-bodied 5-liter Mustangs use this switch that shuts off the fuel. It also works as a good theft deterrent.
Externally mounted pumps for sequential fuel injected applications are available and one of the most proven is this T-REX from Vortech Engineering. This comes as part of the company’s supercharger kits and is a reliable way to ensure timely fuel delivery. It comes as a complete kit, presenting relatively few hassles when the time comes to install it.
Something else to consider is Mass Air Flow. The 1986-1988 Mustang and 1986-1992 Lincoln MK VII H.O. motors came with speed density metering. This works fine on a stock or mildly modified vehicle, but any major changes in airflow, and the computer has trouble matching the required fuel ratio to compensate. If you are planning on further modifications, converting to Mass Air (found on 1993 and up Mustangs) is a must.
Getting the correct wiring harness is crucial for a successful fuel injection conversion. You will also need to make sure you get the computer from the same car as they are designed to work together. If you end up with a mismatched computer and harness, you’ll have no end of electrical and driveability issues.
Harnesses changed during the same model year, as Ford made changes, making some connectors redundant while others were modified for a new purpose. If you’re new at this, get an experienced hand to help you.
On Speed Density cars, the Manifold Absolute Pressure sensor is crucial to calculating air/fuel. Problems in the rubber tubing that connect it to the intake manifold often cause poor idling and rough running.
If you choose to go with a complete aftermarket EFI system, there are a number of options, though most are aimed toward high performance and racing applications, plus you need to factor in the cost, as it can be over $5,000 for a complete system in many cases. These Hogan’s fuel rails are designed for high horsepower turbo or supercharged applications.
Special thanks to Joe Da Silva for his help in preparing this article. Joe has been wrenching on Mustangs and Fords for over 20 years, he’s set national track records and won the NMRA Pro 5.0 World Championship.
Calculating Your Injector Size and the BSFC
Calculating fuel injector size is one of the most misunderstood aspects when it comes to EFI applications. When doing this, one of the most important considerations is determining your engine’s Brake Specific Fuel Consumption (BSFC). This is essentially how efficient your engine is in terms of the amount of power it makes in relation to the amount of fuel it uses. The accepted rule of thumb for normally aspirated engines is a BSFC of .50 while for modified engines it is higher –.55 for those equipped with Nitrous and .65 for supercharged or turbocharged engines, since the extra boost allows these engines to burn more efficiently and use less fuel.
However there are also several givens, that you must assume when calculating injector sizes, one being injector efficiency. It’s widely accepted that an efficiency of 80 percent is accurate, since that is the optimum amount which an engine’s fuel system is considered to operate at under normal conditions, beyond that the injectors become overtaxed, causing heat build up and efficiency to fall off rapidly. So using the formula,
H x BSFC / C x D
H (rear wheel horsepower)
BSFC (Brake Specific Fuel Consumption – the number of lbs of fuel it requires to make 1 horsepower per 1 hour)
C (the number of cylinders)
D (Injector efficiency)
Gives you the required injector size for optimum performance – for example: 300 (hp) x .50 / 8 x .80 will give you approximately 20.9 so in this case you would need 24 lb/hr injectors, which are the closest equivalent size Ford specific injector available, relevant to your calculations.
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