Swapping a Holley Carb for a Terminator EFI System - 950 HP to 950 EFI

We swap a 950 Ultra HP carb for a 950-CFM Holley Terminator EFI system to get this ’68 Camaro tightened up for the twisties

Liz Miles May 14, 2014 0 Comment(s)
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All of these old cars are wired differently from complete wiring harness upgrades, wiring project additions, or both. This particular specimen has a terminal in the glovebox that provided easy access to power, ground, and key-on sources for the main harness. The glovebox also houses the MSD Digital 6 box with the tachometer output the ECU needs to sense rpm. The ECU also needs a heavier 10-gauge power and ground has its own black braided sleeve and comes long enough to go all the way to the trunk-mounted battery in this car, but would be shortened up for an engine-bay mounted battery. The Terminator EFI system has the ability to control timing, fuel pump, electric fans, and A/C compressor shutoff, however, they were unused in this installation. The most intimidating part of the entire installation was deciding where to drill the 2-inch hole in the firewall to pass the main harness through. Once we settled on the spot it was cake from there on. The ECU needs to be mounted in a low-vibration area so we chose to mount it on the top of the heater core housing under the dash.

Throttle Body

In the 550-406 kit is a 950-cfm Hard Core Gray hard-coat anodized throttle body (PN 550-405 is tumble polished aluminum) with four 80-pound injectors located below the throttle plate. This makes for optimum atomization as fuel doesn't need to pass the turbulent throttle plates. This all-aluminum throttle body is styled after the Holley one used in NASCAR's new EFI program. One of the things that makes this kit extra easy to work with is that the sensors and injectors are pre-installed and pre-wired into the unit with one plug. It includes an air temperature sensor, a MAP sensor, a throttle position sensor, and an idle air control motor. Throttle and kickdown hookups are the same as on a carburetor, but two brackets and a set of ball studs are included in the kit in case you're starting from scratch.

950 Cfm Holley Terminator Efi System Harness 2/12

Once we decided what wires would not be used in this installation we fed them backwards into the harness and wrapped it with electrical tape. This made fishing the harness through the firewall easier and kept things organized.

950 Cfm Holley Terminator Efi System 3/12

The most intrusive part of the installation was drilling the 2-inch hole in the firewall to pass the harness through. We drilled a 1⁄8-inch pilot hole in the spot we thought would be best then verified that it was not a problem on the underside.

950 Cfm Holley Terminator Efi System 4/12


With the fuel pressure regulator set to 43 psi and a thorough check for fuel leaks, we are ready for initial startup. The Terminator EFI instructions walk you through using the handheld to do the initial setup. You will be asked questions such as, is your engine smaller or larger than 410 ci; is your camshaft mild, factory, or unknown; do you want to control timing; and a few others. This gives the ECU enough information to set up a base fuel map for initial startup. The last step before turning the key is to do a throttle position sensor sweep. This allows the computer to adjust to your physical throttle sweep. This is a good time to check that you get wide-open throttle, so grab a buddy and have them push on the throttle to the stop after you have it floored in the car. If they can get any travel out of it you will need to investigate why.

Just before twisting the key to cranking position, we verified that the sensor readings were correct on the handheld. Everything was within specifications so it was time to start it up for the first time. You almost expect it not to happen, that maybe you forgot a step or left something unplugged, but it fired right up. The only thing we had to do was adjust the idle speed on the throttle body and off we went on our first drive.

950 Cfm Holley Terminator Efi System Handheld 5/12

The handheld controller included in the kit is all you need to get tuning. Here we start with the “Wizard” selection to start us through the initial setup. Only minimal information is needed; you don’t need to have any experience tuning. The handheld can also be used as a gauge monitor whenever you like. You can follow your O2 readings, coolant temp, or any other engine function that passes through the ECU.


It turns out EFI isn't scary at all. The Terminator EFI system, with bar-none self-learning software built in, made the switch from carburetion to fuel injection effortless. We spent two easy six-hour days on the project with no hang-ups. The first drive out of the shop was a 30-minute mix of highway and street driving. There's no specific protocol for how to break it in or set it up, the instructions are to just go drive. Through high load, deceleration, and cruise conditions, the car ran smoothly with no hiccups. The wideband oxygen sensor and ECU communications did fast work in creating ideal fuel delivery for every condition.

The incentive for this swap was that as an autocross and road racer, being able to stop abruptly and turn sharply without a stumble is incredibly important, and that's what we got. The more we drove it, the more impressed we were by how it performed. The 950 Ultra HP carburetor that was on it was very well tuned and made excellent horsepower on this street/track motor. We were impressed to see the Terminator throttle body felt to produce just as much power but with a smoother cruise and improved fuel economy.

950 Cfm Holley Terminator Efi System 1968 Chevy 6/12

Parts List
Part Number Description Price
550-406 950-cfm 200-600HP Terminator EFI Kit, Hard Core Gray $2,049.95
526-2 Fuel Injection System Kit 699.95
351006ERL 10-foot, AN-6 Pro-Lite 350 Hose (return line) 75.97
AT165106ERL Ano-Tuff 3/8-Hardline to AN-6 male Adapter 9.97
Total $2,835.84


Earl's Performance Plumbing
Bowling Green, KY 42101
Holley Performance Products
Bowling Green, KY 42101


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