Introduction: Nitrous/methanol Injection Wide Open Throttle Switch, Dual Button, Holley Dominator Application.

Picture of Nitrous/methanol Injection Wide Open Throttle Switch, Dual Button, Holley Dominator Application.

This instructable will show you how to build a wide open throttle switch that activates 2 separate switches. This unit is mainly focused on race cars or seriously fast street vehicles. It is made to mount on to a carburetor stud of a Holley Dominator style Carb. I use it for nitrous activation and methanol injection activation. The reason for 2 switches is so you can wire the system to activate your alcohol injection when your nitrous is not armed. It also allows for a very robust redundant wiring of your nitrous system just in case 1 of the switches happens to fail, which can and does happen with the violent vibrations of drag car engines.

The custom pieces of this switch are 3d printed and include a base and the arm. The switches can be purchased from race car part retailers or various retailers such as McMaster Carr. The shouldered screw was purchased at a local hardware store.


1 x 3d Printed base, I recommend ABS plastic for heat resistance and 100% infill for strength.

1 x 3d Printed arm, also recommend ABS with 100% infill.

1 x 10-24 shoulder screw with 1.5" shoulder length, .247" diameter shoulder for .003 clearance in a .250 hole.

2 x button switchs, I purchased from Tim McAmis race cars part # NEW-A-20GQ-B7K

Step 1: Threading the Base and Assembly.

Picture of Threading the Base and Assembly.

This is the only fab work to be done on this project, you will need a 10-24 tap and simply tap the hole where the shoulder screw installs. Then take your 2 switches and install them into the 2 large diameter holes and secure with included nuts. Then simply set the arm into place and tighten the shoulder screw, make sure you use a super glue as thread locker so it does not come loose.

Step 2: Watch This Video to See What It Looks Like, and a Tutorial of Features.

This video shows how I mounted the switch, also pay attention to the arm position which should work fine for all dominator carb's but feel free to adjust to your liking.



scottieK (author)2014-10-28

Added .stl files. Thanks for the heads up peppypickle

peppypickle (author)2014-10-28

Nice project, are you able to share the files you used? Nice video explanation, thanks for posting.

neo71665 (author)2014-10-28

One sexy engine.

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More by scottieK:DIY aluminum investment casting using a 3d printer.Universally mounted phone holder. Can fit into CD-player slot! and other places..Nitrous/methanol injection wide open throttle switch, dual button, Holley Dominator application.
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