Bringing Our LS3-Powered C5 Corvette to Life | Project C5 Corvette | Chevrolet Corvette Z06 | Project Car Updates

We had briefly mulled over the possibility of running the LS3 on the original LS6 ECU, but faced a dizzying array of harness adapters and workarounds. Yes, it can and has been done successfully, as the GenIII computer will run the GenIV LS engine, but electronic countermeasures much be employed.

Notably, the LS6 sends crank position signals to the computer via a 24-tooth reluctor wheel while the GenIV engines like our LS3 use a 58-tooth wheel. This can be worked around with an adapter from Lingenfelter, but it’s just the first in a series of adaptations.

The other big issue involves the throttle body: LS6 and LS3 throttle bodies open in opposite directions and modifying the signal from the stock LS6 throttle pedal and ECU is not really feasible.

You can use a Corvette-spec LS2 throttle body, but finding those for reasonable money is getting tricky and, again, cost and complication creep begin to add up.

Finally, there are a whole host of sensors on the LS3 that must be adapted to the LS6 harness for both position and connector because many of them sit in different locations or have different pin or connector designs.

Ultimately, when the cost of adapters and potential complications began to add up, we looked toward standalone solutions, and the Holley Terminator presented itself as an excellent option.

Starting at a little more than $1000 for the ECU and harness, the Terminator X comes in a variety of flavors, including one for our LS3 crate engine. We added a 6.8-inch-wide pro dash for around $1200 that slots brilliantly into the space left behind by the stereo–as this was becoming more of a track-focused car, our need for tunes not produced by explosions had diminished.

Jesse Spiker at Spiker Motorsports–who’s not only our pal but spends much of his days installing Holley ECUs in everything from celebrity-owned restomods to full-race Hellcats–did our wiring and install, placing the Holley ECU in the rear part of the left-front fender, behind the wheel well liner–essentially in the same spot as the factory ECU but on the other side of the car.

The car was wired with a hybrid of the original ECU–which still controls or monitors many body and chassis functions like fuel level and door locks and lighting and whatnot–and the Holley, which controls all the engine systems.

Once we loaded a startup tune into the Terminator (and fixed some improper fuel pump wiring), the LS3 barked to life as soon as it had fuel. We did a bit of pre-start cranking to ensure that the Aviaid dry-sump system was supplying the engine with lubrication, and within a few cranks we were seeing 15 psi of pressure just from the starter spinning the engine over. Once we were confident that the engine was properly lubricated, we gave it some fuel and it instantly came to life.

Now comes the fun part: sorting and tuning. We’ll spend some time on the dyno getting a decent tune on the car, then head to our test track for some increasingly aggressive laps to put some miles on the engine.

After some break-in mileage, we’ll change the oil to a proper synthetic track product. We also need to change out the break-in fluid in our freshly rebuilt GearFX-prepped rear end fitted with the fancy new WaveTrac diff.

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