Upgrading your carbureted engine to EFI


The lowly carburetor has been feeding internal combustion engines since their invention. As a reactionar­y device just trying to feed the motor they were strapped to, they worked well, until said motor started moving… like in a truck. Sloshing fuels and differing altitudes caused manufactur­ers to place

additional reactionar­y devices to keep the air/fuel ratio on a level playing field and drivers from pulling their hair out. These worked about as well as any band-aid and we, the people, suffered through it until a pro-active fuel delivery system came around… and electronic fuel infection (EFI) was born!

For the modern gearhead, the advent of an affordable, easy to install fuel injection system changed the automotive aftermarke­t landscape. Algorithms capable of self-learning and on-the-fly tuning are what really brought leadingedg­e technologi­es used by the OEM’s into the garages of DIY’ers like us.

With the mass influx of these systems available, it can be hard to wade through the options and know which is best for your applicatio­n. We’re going to try and clear some of this mess up, and give you a baseline of what to look for when you are thinking of stepping into the modern century with your old school off-road rig.

For our purposes, we selected two pieces of yard art that would do nothing but kill off mosquitoes with plumes of black smoke when off camber, on a bumpy road, or trying to make it over a high mountain pass; our trail rig Stinky Jeep has a high compressio­n 407 ci V8 with a Nitrous Express direct port nitrous system set to slaughter any hill or snow bank, and Ian’s Jeep J10 pick-up with what is essentiall­y, a bone stock AMC 360.

We made a call to Summit Racing for two completely different Throttle Body EFI systems and selected them specifical­ly for their intended vehicles; a Holley Terminator PN 550-406 and a Summit Racing Max EFI500 PN SUM-240505 throttle body injection system. We also scooped the proper fuel lines and fittings required to feed these systems sticking with Earl’s Vapor Guard products. We don’t want to deal with future leaks and wanted a hose and fitting system that could hand the abuse and chemicals.

Speaking of fuel systems, Stinky Jeep already has a stout Radium Engineerin­g fuel sump system capable of feeding many more horses then we can afford, but Ian’s J-10 does not. We have used Edelbrock’s Fuel Sump systems in the past with great success and ordered another when we had Summit Racing on the line. We won’t go into great detail, but the factory, low pressure mechanical pump feeds the Edelbrock Sump and a built-in, and internally regulated fuel pump feeds high pressure gasoline to the EFI throttle body. No noisy external pump, no custom tank, no fuel return lines, no external regulator. Just a simple fuel delivery system that uses the existing lines and pump.

Summit Racings Max EFI500:

The Summit Max EFI500 unit is designed to be an all-in-one, easy to use selflearni­ng system for engines producing less than 500 Hp and can have you up and running within a few hours after answering a few questions. The J-10 with a stock smog era V8 would have a hard time giving up over 200 hp at the tires on a good day. The goal of this endeavor was to provide a reliable base line for a truck that is driven daily back and forth to work. Easy starting, limited warm up time, and a double digit mpg fuel economy were our primary goals, and we were not disappoint­ed.

The 4150 style mounting flange is a typical standard for almost all throttle body injection units and requires an adapter or new intake manifold to mount the EFI500 unit to the 360. Ian had scooped a new aluminum intake for the old AMC motor, which was lighter, more efficient and allowed for an easy bolt on. SCORE! The wiring harness is well made and only requires a few extra connection­s such as an O2 sensor, water temperatur­e sensor, ignition trigger source, along with constant and switched 12 VDC power sources. All sensors are included in the kit along with the small ECM (electronic control module). A small handheld touch screen is used for the initial setup but can then be used for monitoring the system or removed completely.

A constant feed of 58PSI fuel is required to supply the unit’s -6 AN fitting on the fuel rail. This is not a feed through style system, so a return line is not required, and with our Edelbrock Sump pump, we didn’t have one. The unit is not capable of E85 Ethanol, but we are sure that with the popularity of the fuel, a tune and setup will be available in the future.

There are provisions on the throttle body for connection­s to multiple accelerato­r cable types as well as connection­s for automatic transmissi­ons. If you have an electronic­ally controlled automatic transmissi­on, you will have to purchase a separate controller for that. Vacuum connection­s for distributo­r advance, power brakes and PCV valves are built into the unit as well.

After final connection­s were made and some quick questions by the preloaded software answered, we were very happy to hear the once problemati­c V8 easily come to life and roll into an idle so smooth we had to make sure the truck was running. Once up to temperatur­e, we set the idle and calibrated the throttle position sensor. The included instructio­ns don’t say just how long it will take for the system to learn your particular vehicle, but from our experience, plan on two tanks of fuel of normal driving. This means take it easy… No running from the cops or entering an ultra 4 race the morning after you install the unit. Consider it “bonding time”, and you will be rewarded with all the on- and off-road benefits that fuel injection can offer.

Holley Terminator:

Similar to the Summit Racing Max EFI500 from the outside, the Terminator offers all the benefits of the EFI500 as well as many more… hence almost double the price tag. We chose the Holley for the nasty rollerized motor in Stinky Jeep over the Summit brand for a number of reasons that we will touch on a little later.

The installati­on is basically the same as before; a 4150 style carb flange is needed and a fuel system capable of feeding the 600 hp unit is required at 45 PSI. An O2 sensor, water temperatur­e sensor, and the usual power and ignition connection­s all plug into the nicely made harness. The ECM (which also easily plugs into the harness with a watertight connection) is where the two systems diverge. The Terminator comes with a very intuitive self-learning program but can also be manually altered for free with Holley HP control software from a laptop with a USB port. Multiple inputs and output can be configured for anything from cooling fans, to fuel and oil pressure feedback and even analog nitrous control. Have a complex pulse width modulated fuel system? Have a turbo charger or supercharg­er attached to your engine? Want to adjust ignition timing? Use the system water temperatur­e sensor to control electric fans? Want a switch to raise the idle by 500 RPM for an air compressor? The Terminator can do all of these with ease.

Our 408 V8 was initially configured and wired to control the two fuel pumps and electric fans connected to the motor. The nasty, high lift cam, high dynamic compressio­n, and lumpy idle provided very few issues with the initial running of the system but did require some minor manual tweaks that could not be done with the EFI500 platform. Starting the motor is simple and requires little to no warm up before taking it out driving, the same as a new school vehicle with modern EFI.

Although we run a standard transmissi­on, the Terminator is capable of operating both cable, vacuum and with the proper provisions, electronic­ally controlled transmissi­ons.

Our minimal experience with the Nitrous Express system on the rig was another major draw for the Terminator as the system can be used to turn the system on only when the accelerato­r is at wide open throttle (WOT) and above a pre-determined RPM (3000 in our case). This negates having a separate nitrous controller AND we can have the Terminator enrich the air/fuel ratio when the system is on, just to keep our high dollar engine intact. We’re always changing things and experiment­ing as well, so the ability to use the same EFI system and controller for multiple uses appeals to us greatly.


The convenienc­e and drivabilit­y of modern EFI cannot be argued and if you are in the market to upgrade your old offroad truck with a new induction system and carburetor, you owe it to yourself to look into the multitude of self-learning EFI systems available. Admittedly we chose from two alternate ends of the spectrum of throttle body injection system in terms of price, but like your favourite pair of underwear, this is not a “one size fits all” situation.

Summit Racings Max EFI500

system is a basic unit, perfectly suited for a simple carburetor swap to improve the off road prowess of any simplistic, carbureted rig. Ian’s J10 Truck fit the bill to a “T”.


Affordable Easy to install Excellent self learning algorithms Simple setup


Unable to operate with power adders (Boost, NOS, Methanol, etc.) Cannot operate with low engine vacuum/large overlap cam shafts Not manually tunable No provisions for auxiliary equipment

The Holley Terminator was brought to market for the performanc­e crowd and the average gearheads inability to leave well enough alone, we and our axle snapping V8 fit in this category like boggers in mud.


Adaptable to multiple engine, transmissi­on, fuel and ignition systems Can be upgraded to Holley HP for additional tuning with a laptop Works well with power adders Able to accurately feed 600 hp engines


Almost 2X the price of an entry level system Installati­on requires slightly more wiring Many more parameters to take care of Needs to make a minimum of 250 HP

No matter the system you choose, we have yet to run into a system on the market that was not light years ahead of the old gas dumper sitting atop the engine it replaced. Our final advice is to look at the pro and cons listed above and stick with a name brand you know and trust. Like many things in life, it’s better to have more options and not need them, than need them and not have them, and these have the minimum required and more. Follow along as we highlight the installati­on and running of these two systems and get ready to hit the trail.

Summit Racing Equipment – www.summitraci­ng.com

Holley Equipment – www.holley.com

Edelbrock – www.edelbrock.com

Four Function Autosport – www.fourfuncti­on.ca

We were not really expecting an increase in power by swapping the old carb for EFI, but were presented with it anyway. The additional air and fuel the motor could now eat pushed the average power up by roughly 20 hp. Throttle response and overall drivabilit­y were the real winner as well as being able to drive at almost any angle. We haven’t had a chance to cold start the Summit Racing unit yet, but can attest that the Holley sparked up and burbled into an idle, ready to hit the snow every morning we tried.

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 ??  ?? 1. Two boxes from Summit Racing are all that we need for the weekend shenanigan­s of swapping the old carburetor out of Ian’s rusty J10 pickup truck.
1. Two boxes from Summit Racing are all that we need for the weekend shenanigan­s of swapping the old carburetor out of Ian’s rusty J10 pickup truck.
 ??  ?? 11. Watching a set of unbalanced Super Swampers howl on a chassis dyno is an amazing experience and we fully recommend it…. from a distance… with a helmet on… and maybe a mouth guard. 11
11. Watching a set of unbalanced Super Swampers howl on a chassis dyno is an amazing experience and we fully recommend it…. from a distance… with a helmet on… and maybe a mouth guard. 11
 ??  ?? 10. To get some actual numbers, we headed down to Four Function motorsport to leak oil and purge grease all over their fancy dynamomete­r. We first ran a few tanks of fuel though the truck driving on the street so that the computer could learn the engine it was now attached to. 10
10. To get some actual numbers, we headed down to Four Function motorsport to leak oil and purge grease all over their fancy dynamomete­r. We first ran a few tanks of fuel though the truck driving on the street so that the computer could learn the engine it was now attached to. 10

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