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Electronic Fuel Injection Retrofits for Your Street Rod or Muscle Car

2/26/2021
You have Decided to go EFI, so What is Next?

There are many reasons why an automotive enthusiast has decided to update their ride, ditching their carburetor for electronic fuel injection of some sort. Whatever your reason is you have landed here on our buyer’s guide looking for a little help and a whole lot of answers. Do not worry, that is what we are here for; to provide a little guidance and answer all those questions you have bouncing around in your head. What we will not be discussing here is carburetion vs fuel injection. The carb vs EFI debate has been discussed ad nauseum.

Retrofitting your ride’s engine with an EFI retrofit is a big step in enjoying the time behind the wheel. With a fuel injection conversion, you will enjoy better cold starts (hot starting too!) along with better throttle response and drivability. We know updating your ride with an EFI conversion kit and the supporting hardware that goes with it is not cheap, and while prices have come down over the years while features and quality have gone up, it is still quite the investment to add fuel injection to your muscle car or street rod. That is why we are here, to help you work through these questions and determine the best EFI system for your needs!

How Much Horsepower Are You Looking to Support?

Just like a carburetor, fuel injection retrofits can support only so much horsepower. Factors like venturi size, injector flow rating, and more effectively put a horsepower “cap” on a specific product part number or product series. If you will be exceeding the recommended horsepower rating you have the option of upgrading to a larger unit capable of handling more horsepower, or in some instances adding a second unit, going “dual fours” if you will, with the retrofit throttle bodies.

For the average street performance application, you will find a single 4-barrel style bolt-on EFI retrofit capable of handling 200-600 horsepower from all the major players in the market like Holley Sniper EFI, FiTech EFI (seen here), FAST EFI, and so on. These all-inclusive self-tuning systems are relatively easy to install on any engine and can really make driving your classic car or street rod fun again.

As performance needs increase your options will narrow some, but you will still easily find systems capable of handling over 1,000 horsepower and we are going to bet that is a slim minority of our customers when it comes to street rods and muscle cars. Suffice it to say, whatever you are making under the hood, be it a 200 hp inline-six or an 800 horsepower stroker big block Chevy, you can update it with fuel injection and reap all the benefits.

Are You Using a Supercharger or Turbo?

All the bolt-on throttle body injection retrofits on the market today provide similar abilities with features like a built-in fuel pressure regulator, direct-mount ECM, cooling fan control, engine timing control, and more. Features begin to differ, however, at the higher horsepower applications since these models are generally fitted to performance vehicles that mandate such additional needs as launch control, timing retard, nitrous control, programmable inputs/outputs.

While nitrous can be controlled with a stand-alone controller and fuel enrichment (wet system) when it comes to draw through or blow through forced induction it is imperative you choose the correct EFI kit capable of handling the horsepower and boost pressure, while providing boost-sensitive tuning capabilities. These upgraded retrofit systems usually rely on a different map sensor, boost referenced regulator, and additional software tables to control fuel/timing by boost, and more. While most systems, like the FiTech fuel injection, utilize a hand-held touchscreen for tuning, more performance-oriented models often allow tuning via a free software package you install on your laptop, like Sniper EFI, which uses the software from Holley EFI. This allows for much finer tuning to not only extract the most performance, but to completely fine tune spark and fuel tables in relation to coolant temperature, air fuel ratio, boost pressure, and more. This is often handled on a chassis dyno with a custom tuner, but with a little reading and help from the multitude of tech forums these systems have, you can tune your own EFI system via laptop with much success. Edelbrock EFI kits are unique in that they can be had with an optional tablet (seen here). A great solution if you wish to have a dedicated larger screen to use for on the go tuning of your vehicle.

What Fuel System Will I Need for my Horsepower Level?

Carburetor fuel systems are relatively simple. They usually use a mechanical fuel pump driven off the engine to draw fuel from the tank to produce a 5-7 psi fuel supply to the carburetor. Of course, there are aftermarket pumps and regulators and all manner of bits that can upgrade the carbureted fuel system, but none of it can produce the fuel pressure and volume required by a fuel injection system.

Fuel injection requires a high-pressure fuel system capable of supplying 40-60 psi of fuel pressure. Because of this you will need to upgrade your mechanical fuel pump to an electric fuel pump. Your two main options are in-tank and external (usually mounted on the frame rail or elsewhere under the car). The in-tank design is preferred and there are several ways to accomplish this, from retrofit pump assemblies that you drill a mounting hole for in your current tank, to fuel injection specific replacement fuel tanks (shown here), and more. An electric fuel pump is just one component of the new fuel system needed to support your fuel injection retrofit.

Holley's EFI Fuel Tank Modules are a great solution for EFI fuel delivery needs if you don't want to mess with replacing your complete fuel tank. These modules simply replace your fuel pickup/float assembly and provide a self-regulated pump for a returnless-style fuel system compatible with most any aftermarket EFI retrofit system.

Additional components required to deliver the fuel to the fuel injection system will include the fuel lines and of course a filter. Fuel lines can be steel or rubber, but they must be rated for EFI fuel pressures (more a concern with rubber, but something to consider with steel fittings/adapters). Unlike carbureted fuel delivery with just a single feed line, the majority of EFI retrofit systems utilize a full return-style fuel system, meaning the regulated/unused fuel is returned to the fuel tank via a second line. This line can be smaller than the feed line, as it carries little to no pressure, however for installation ease and product ordering needs most installers will fabricate the supply and return lines from the same materials and inside diameter, which for typical street applications should be 3/8-inch (AN -6 for those using AN line and fittings).

A really trick little product we've come up with here at Speedway is this LS fuel filter and regulator combo. We made it with AN -6 fittings so it works perfectly with aftermarket AN fuel lines without having to buy or use adapter fittings and keeps the return line short, as it only has to travel from the filter back to the tank. Don't let the LS name fool you though, this will work great with most any EFI retrofit using the same fuel pressure requirements.

Fuel filters for a fuel injection system are a bit different than what you may be used to with a carburetor. You will find in-tank pumps use an integrated filter “sock” of some design, while an external frame-mounted inline pump will need a separate 100-micron pre-filter to protect the pump. The second filter, downstream of the pump and before the regulator should be a 10-micron post-filter unit that is used to filter even smaller materials that may damage the sensitive internals of the fuel injectors. There are several options available, from single-use replacement filters to filter housings that use rebuildable components with cleanable or replaceable filter media. You can find suitable fuel system components from all the major EFI manufacturers and many offer complete kits with the throttle body injection unit, fuel pump, filters, lines, fittings, and more under one part number.

Is Datalogging Important to You?

The retrofit fuel injection systems we offer work in conjunction with a wideband oxygen sensor that is included with the system to facilitate real time air fuel ratio adjustments. This sensor, along with other inputs aids in the self-learning capabilities of these systems. However, the self-learning feature, as good as they are, cannot easily factor every single combination that these systems may be bolted to. In some cases, additional tuning via the included touch screen or a laptop and the manufacturer’s software will be necessary over and above answering the basic setup questions of engine displacement, cam type, etc. It is uncommon, but it does happen, especially with radical camshaft profiles and other engine oddities.

One way to determine exactly what changes your combination may need to run at its peak best is to datalog the fuel injection while driving the vehicle. All the major retrofit systems provide datalog capabilities through the included handheld controller. This allows evaluating the log post drive cycle on a computer. Software for your computer is available from these manufacturers to read these datalog files or to datalog directly to the laptop while driving or on a dyno. It is our opinion, especially with the proliferation of affordable laptops/tablets these days, that downloading the software and datalogging along with real-time laptop tuning will net you the best experience. The self-tuning will get you close, but to extract the most performance and best drivability custom tuning is your best bet.

Throttle Body vs. Sequential Fuel Injection—Is the Extra Cost and Installation Worth it?

Your typical 4-barrel EFI retrofits have blossomed in popularity over the years due to their ease of install and self-tuning capabilities. If you can change a carburetor base gasket you can install one of these retrofit units. They work extremely well in most cases and live quietly under your typical 14-inch diameter chrome air cleaner that all muscle cars and street rod fans love while providing better drivability, performance, and more. That said, they do have their limits, especially regarding performance and efficiency. Going to the next step, sequential multi-port EFI is certainly a consideration for some combinations.

The 4-barrel retrofit systems still mix the air and fuel above the throttle plate and rely on a “wet manifold” design and the vacuum from the piston’s downward force to pull the mixture into the combustion chamber. Just like with a carburetor, fuel can puddle in corners or get hung up in the intake runner, falling out of suspension and creating issues. The 4-barrel EFI retrofits use four to eight injectors right at the throttle plates and are a combination of convenience, cost saving, and performance, but a true sequential fuel injection system (where the injectors fire in relation to valvetrain events) can provide more tuning ability, more performance, and more efficiency, but at the cost of more installation time and greater product expense.

Unlike the 4-barrel EFI retrofits, which replace your current carburetor, the sequential multi-point fuel injection systems require updating the intake manifold itself. While not a scary proposition for the typical automotive enthusiast with a toolbox full of tools, it does add complexity, cost, and installation time. The multi-point fuel injection system places the individual injector at each cylinder head intake port, spraying directly at the back side of the intake valve. This means the manifold is “dry” and only moves the incoming air. The injector spraying the fuel directly at the valve means the system does not have to rely on the piston to pull the mixture into the chamber.

Furthermore, with a sequential fuel injection system injector duty cycle (what some would call on time or dwell time) can be adjusted at each cylinder via the tuning software. Most multi-port EFI retrofits use a cast or even a welded sheetmetal manifold with a bolt-on throttle body that will modernize the under hood looks of the car, but you will still find multi-point fuel injection systems with a “carb style” central throttle body that will still accept your traditional 5-1/4-inch air cleaner flange to maintain those classic under hood looks like this Cobra replica seen here. If your budget can swing it, we highly recommend considering a sequential fuel injection retrofit, but if budget is tight or you have a unique factory manifold, etc. you wish to maintain, then the 4-barrel EFI retrofits are your best bet.

How do I control Factory EFI Setups Found on LS and Coyote Crate Engines?

There is no denying that crate engines are a major part of today’s hot rodding. There is just something about maintaining a classic car’s timeless body lines but powering it with a modern fuel injected engine, overdrive transmission, and power accessories to make it a great handling and driving vehicle. Most of us are not getting any younger and want to be able to enjoy our street rods and muscle cars with power steering, comfortable seating, air conditioning and more, and today’s modern crate engines help motivate many of these “restomod” style builds.

When you crack open that crate engine it will usually be topped with the production composite intake manifold with throttle body, fuel injectors, fuel rails, and sensors. In a nutshell all you really need to run the stock fuel injection hardware is a compatible ECM and wiring and a suitable fuel supply system like we discussed above. While GM, Ford, and Chrysler all offer their own kits to power their respective engines, the aftermarket has answered the call from their customers to create kits with ECM, wiring, and more to power up these engines.

These fuel injection systems maintain the sequential fuel injection configuration, and in most cases retain such things as variable cam/valve timing setups, either directly or through an add-on control system. While internally very sophisticated with a lot of features, their installation truly is not much more difficult than your typical hot rod wiring kit. The included harnesses are pre-terminated for all the factory sensors, so the harness simply plugs into all the crate engine’s inputs and outputs like coolant sensor, injectors, drive-by-wire throttle body, and so on. You will find crate engine solutions from Holley EFI, FAST EFI, Edelbrock, and others.

Holley Sniper EFI vs. FiTech GoEFI—Which Fuel Injection System is Best?

Both 4-barrel EFI retrofit systems are easy to install and not terribly hard on the wallet. You can find systems from both companies that will handle your typical street performance engine as well as the extreme high horsepower and supercharged or turbocharged setups. Where things begin to narrow on choices will be in such factors as multiple throttle body configurations. FiTech EFI offers both dual quad and tri-power EFI setups, yet Holley’s Sniper EFI only offers a dual quad configuration. As for software/tuning support Holley has a diverse network of custom tuners/dealers and a mature software package that is used across all Holley EFI products, providing a large base of users to trade tuning information with.

When it comes to self-tuning both systems use a similar, if not the same, wideband O2 sensor. However, if you are planning on custom tuning (and you really should) this is where the systems differ once again. The Holley Sniper EFI touchscreen handheld provides a great startup wizard, but all custom tuning must be handled through Holley’s free downloadable EFI software and a laptop or tablet. The FiTech fuel injection system allows for entering initial startup parameters as well. Though we would not quite call it a “wizard” it does ask similar questions such as displacement, cam type, base idle rpm requested, etc. Where the FiTech EFI does stand out is it allows tuning right through its handheld device. Besides basic tuning FiTech offers its Pro Tuning software directly on the handheld. You can further tune your FiTech via the handheld or connect the handheld to your laptop and transfer/install the software directly for even more flexibility.

At the end of the day, it is a tough call to say which one stands out head and shoulders over the other. We will say we feel the FiTech is more adaptable to street performance applications with a nod towards easier tuning for the average car enthusiast, while the Holley products have a huge technical support library with robust software and have been proven in extreme horsepower applications, including racing venues. So, knowing your retrofit EFI’s intended use, the specs of the engine it is going to be mounted to, and an honest evaluation of your tuning skills, should help direct you to the system that is best for your street rod, muscle car, or race car.

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