8/11/2026:  More on the electrical system

This blog update will be longer than usual as there is a lot to document.

The electrical system has basically two components: the wiring harness that I got from Ron Francis and the Holley Sniper wiring.  The Ron Francis hwaness has segments that mate together: a rear harness that powers the lights and fuel pump, the front harness that powers the front lights and fan and the  ‘engine harness’ that connects the engine and main battery to the central harness.  The main harness has a fuse box with relays and basic routing of power from the battery.  Additionally, I added a second fuse box to direct power to things like a trunk light, the rain light and the foot-box fans.

The Ron Francis harness is a solid ’template’ for the electrical system but I’ve had to modify it quite a bit.  If I were to do another car like this, I would probably just create my own wiring loom.  But, being a neophyte, the RF loom has been reasonably helpful. The spreadsheet, below, shows the primary connections in the mating of the Sniper and RF harnesses.

The orange lead on the RF harness is a 12v supply for the coil positive. The Holley Sniper also requires a 12v ‘pure’ signal. Factory Five forum members suggest splitting off the 12v from the orange RF wire and running one segment to the coil pos. and the other to the pink Holley Sniper power in wire. However, Holley wants 12v that are not affected by other uses. As such, I used the orange 12v to trigger a relay directing 12v direct from the battery to the Sniper. This setup is shown in the schematic to the left.

Another substantial modification to the electrical wiring concerns the way in which the battery power to the Ron Francis (RF) harness and starter solenoid is routed.

The photo to the left shows the starter solenoid, with three terminals, nested against the starter. The lower terminal on the right on the starter solenoid connects to the starter motor with a single large gauge wire. The solenoid has two other terminals: a large one with a 3/8” stud and a smaller one down to the left.

The RF harness has three wires that need to be energized by the battery: the alternator feed, the ignition feed (going to the ignition key) and the power feed to the fuse block for distributing power to other car needs.  As originally configured, the lead from the battery is connected to these three RF leads by being joined at the large terminal on the solenoid. This means that three large gauge wires are crowded on to the 3/8” terminal.  I originally had the four wires on the single stud but concluded that the arrangement was just too tight.

An alternative is shown below in the schematic.

The main battery feed goes initially to a master cutoff switch.  When in the ‘on’ position, the battery feed is split with one branch going to the 3/8” terminal on the solenoid and the second going to a power distribution buss hosting the three RF harness feeds and the 12 v of ‘clean’ power needed for the Holley Sniper.  For the ignition, the power route is from the battery through the cutoff switch, to the ignition switch and back to the starter solenoid once the ignition is turned ‘on’.