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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We love our carburetors. For the last 12 years the owner of this 357ci small-block Chevy-powered '68 Camaro has rocked a Holley carb; for the last eight, it was a 950-cfm Ultra HP. This thing worked great, even on the street. It went drag racing, to the road course, the autocross, on early morning car show departures, and late-night cruises. The truth is, these “old technology” fuel dumpers just plain work. However, today's EFI systems make it easier than ever to make the conversion.

The decision to make the switch from a good ol' Holley carburetor to fuel injection isn't easy for someone who has never used it before. Sure, your daily driver has fuel injection from the factory, but many of us haven't been hands-on with something aftermarket. We try and keep our hot rods as simple and clean as possible, and adding an entirely new system to it with wires and stuff can be a little bit intimidating. The benefits of smooth, cold start-up, constant idle during braking, smooth fuel delivery under hard turning, and maximum efficiency outweighed reservations about the switch to fuel injection.

Meet Holley's Terminator EFI system (PN 550-406). It's a throttle-body injection system that is a direct replacement to your square-bore carburetor and includes everything as far as the wiring, the sensors, the computer, the handheld controller, and the throttle body itself. We also got the optional fuel systems kit (PN 526-2) to retrofit the Camaro for high fuel pressure. The fuel system kit includes Holley's billet in-line fuel pump, billet fuel pressure regulator, pre- and post- billet fuel filters, 20 feet of Earl's Pro-Lite 350 fabric braided hose, and enough Ano-Tuff hose ends and adapters to stitch it all together.

We kick off the installation at Scott's Speed and Custom in Antioch, California. If you've been reading this magazine over the last couple years, you may remember a couple of builds turned feature cars that came from this shop. They were nice enough to lend a lift and a hand in getting this project started and wrapped up in two easy days.

Fuel System

Day one was plumbing day. The Camaro already had a Holley Blue electric pump so the wiring for an electric pump was already there. The needs are basic: power, ground, ignition power, and a relay. The fuel pump signal wire and relay is within the Terminator EFI wiring harness so all you need is a chassis ground near the pump.

After plucking the 10-year-old Holley Blue, we built a bracket out to mount the Holley billet in-line fuel pump (PN 12-700) between the gas tank and the differential about one inch above the bottom of the tank level. As the fuel system kit suggests, we attached the 100-micron billet fuel filter directly to the inlet side of the pump.

The fuel tank had a large diameter fuel outlet previously welded to the bottom of the tank to bypass the six-cylinder Camaro's original 5⁄16-inch fuel line. We used the same outlet with this kit but a factory one of 3⁄8-inch or better would have been fine.

From the pump we routed the AN-6 Earl's Pro-Lite 350 fabric braided hose along the inside of the framerail to the firewall where we installed the 10-micron billet in-line filter. We continued the line to the throttle body, which was loosely set on the carburetor studs for the fuel system mockup. The throttle body has two AN-6 fittings on it, an in and an out. We connected to the remaining fitting and ran a second line rearward to the firewall where the billet fuel pressure regulator sat. Lastly, a second run of AN-6 Pro-Lite, purchased separately, went all the way back to the tank as a return.

950 Cfm Holley Terminator Efi System Filter Pump 2/12

The pre-filter/pump assembly is attached to a plate with four rubber grommets as insulators. They aren’t necessary but it does keep any vibrations from transmitting to the frame.

950 Cfm Holley Terminator Efi System Fuel Pump Positive Negative 3/12

The positive and negative wiring on the fuel pump is crucial to get right. That’s why we’ve made the connector styles opposite so they could never be reversed. This is a good tip for any removable component wiring.

950 Cfm Holley Terminator Efi System Fuel Pump 4/12

This is our fuel pump bracket made out of mild steel scraps. The angle of the upper plate mimics the trunk floor directly above the gap between the tank and the rearend housing. You can also mount the pump to the framerail as long as it’s level or below the lowest part of the fuel tank.

That brings us to the return line issue. There are a couple ways we can re-introduce fuel into the tank. In this case, since we already had an auxiliary outlet to work with, we could use the factory pickup fuel outlet as the return. We used Earl's PN AT165106ERL, also ordered separately, to convert the hardline to AN-6 for easy hook up. We did need to drop the tank for this part because of where the fuel lines were, so don't roll into this project with a full tank of gas like we did, oops. You can also install a bulkhead using fuel-safe nylon or rubber washers on the pickup plate to add a place to dump return fuel. Another option is to use Moroso's EFI filler neck tube return kit (PN 65385) that adds a fuel line barb to your filler neck for the return.


There are only two sensors outside of the throttle body that need to be installed: an engine coolant temperature sensor and the wideband oxygen sensor. The coolant temperature sensor is a basic 3⁄8-inch pipe thread that will fit into a cylinder head coolant port or one on your intake manifold. The oxygen sensor needs to go in a header collector, if equipped, or an exhaust pipe close to an exhaust manifold. It needs to be placed 10-degrees above the midline of the tube. This protects the sensor from damaging condensation that collects in cold exhaust tubes. Before you drill a hole, also consider clearance for the sensor and the wiring. We used a step-bit to make the 7⁄8-inch hole, ground the ceramic coating away from the edges, and MIG welded in the threaded bung included in the kit.




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