We were given the opportunity to put some finishing touches on Rex's 77 Camaro. This had been a family project that Rex, his son, and his father in law put together, with a 383, Vortec heads, and a small cam. Rex had found a great Holley Sniper EFI system that complimented his goals for the car.
The Sniper EFI system is similar in functionality to a Holley HP, however, everything is integrated into the form factor of a carburetor. The system comes with a handheld programmer, in addition to a USB cable for more granular control.
For full digital control over both fueling and spark, to make this car drive like a modern EFI vehicle, we were asked to install and pair a Holley Hyperspark Distributor with the Sniper system.
In order to get the Hyperspark set up correctly, we need to make sure the car started and idled properly at all operating temperatures -- That way, if we had issues, we knew that we're troubleshooting a "Hyperspark" issue rather than an existing "Crank - No Start" issue. The Camaro started and drove to the shop, however subsequent attempts to start when up to temperature were unsuccessful. I had to come back to the shop in the late evening to get the Camaro to fire and pull into the bay.
We hooked up our logging equipment, and noticed that the coolant temperature measured by the Holley did not match up to the actual temperature of the block. Coolant temperature was around 210* according to a mechanical gauge, but was reading ~130* in the ECU. We found that the coolant temp sensor was threaded into a hole in the lower plane of the intake manifold, that was not exposed to coolant. We sourced a few brass fittings to move the sensor, topped it off coolant, and made some adjustments in the tune to get the Camaro to start a bit better. Subsequent starts were still difficult, and inconsistent. The motor would crank, fire, and if you let off of the key quick enough, the motor would continue to run. This pointed us to find out that the Holley system / relays were only powered in "Run" and not "Crank".
As soon as the starter would turn, the Holley would lose power. The motor was firing only from the fuel system's priming pulse, and if you were able to release the key quick enough, the Holley would boot up and start to inject fuel. It's a testament to the flexibility of the Holley system that this car started and drove 45 minutes to the shop!
Next, we identified good mounting locations for the Hyperspark system. The larger control box would sit on the passenger firewall, and the coil would sit on the opposite side of the engine bay, next to the wiper motor. This allowed us to hide most of the wiring behind the engine and under the cowling as much as possible, while keep the high-voltage coil away from sensitive electronics, and allowing for easy serviceability.
It was time to build a new harness for the Holley systems. I ordered a set of relays with pigtails, a fuse block, and the Rex's preference of split-loom. Our intent was to hide as much of the wiring in the fender well, to keep this installation looking as vintage as possible. We added an additional 40a fused circuit for the radiator fan, and included provisions to drive the fuel pump from the same harness as well.
To trigger our relays, we moved our Switched Power source to the ignition power feed on the old distributor, since it is hot in both Run and Crank. We set the motor to Top-Dead-Center, and began installation of the Hyperspark Distributor.
We ended up with a well documented, safe, and discrete Holley EFI installation. The Camaro turned out great, put down a solid power curve, and now starts and drives like a vehicle off of the showroom floor.