Holley EFI 12.3 inch Pro Dash
Holley 12.3 Pro Dash: size, mounting and custom layouts
The 12.3 inch Pro Dash is Holley's big digital dash. It fills the space of a full gauge cluster, reads everything from your Holley EFI, and lets you build your own screens. Here's what to know before you mount one and how to make it look like it came with the car.
How big is the Holley 12.3 dash?
Holley lists the 12.3 inch Pro Dash at about 11.5 inches wide by 4.25 inches tall. That's roughly the footprint of a speedometer, tach and a row of small gauges in a classic cluster, which is why it drops into so many trucks and muscle cars.
The screen is wide and short, like a long strip. Layouts that work best put two big dials side by side and tuck smaller gauges or digital readouts around them.
Mounting the 12.3 Pro Dash
Holley gives you two ways to mount it, and the kit comes with a paper template for both:
- Surface mount: bolt the dash to a flat panel or bracket using the six threaded holes on the back.
- Flush mount: cut the panel along the template's cut line so the dash sits recessed. This takes more fabrication but looks factory.
Plenty of builders use a bezel or dash panel made for their car, or have one fabricated. Whatever you choose, lay Holley's template on your dash before you cut anything and make sure you have room behind it for the wiring.
What the stock screens can and can't do
Out of the box, the 12.3 dash comes with a set of ready-made screens, and it picks screens to match your ECU the first time you connect it. You can edit any screen right on the dash: add gauges, move them, change what they show and swap the background.
Editing on the dash works, but it's slow. You're dragging gauges around with a fingertip in the car, one at a time, and a custom background almost never lines up with the needles on the first try.
Making the 12.3 dash look custom
That's what the Gauge Garage designer is for. You build the whole screen on your computer: pick a style, drag gauges into place, set your redlines, add your logo, and download it. Then you load it onto the dash from a USB stick.
- Gauge faces, tick marks and numbers in any style, from white classic faces to carbon fiber race gauges
- Needles that line up with the numbers, because the designer sets both at the same time
- Big digital speed, bar graphs, warning lights and a shift light bar
- Your own background photo or shop logo
Want ideas? Browse the layout templates or start from a layout for your build, like a C10, Fox body or G-Body.
Will a 12.3 layout work on the 6.86 dash?
Yes. Both Pro Dash sizes use the same screen resolution, so a layout loads on either one. On the smaller dash everything shows up a little over half the size, so small text can get hard to read. See the 6.86 Pro Dash guide for tips.