TACHVAC - The Perfect Gauge in the Perfect Place

Courtesy of Eugene Fisher

The Pacific Cruisers GMC Club several years ago contracted for and bought several TACHVAC gauges shown below. I saw them in member coaches and wanted one for my GMC. The tachometer and vacuum functions of this gauge are ideal for GMC owners. This meter will enable you to keep the engine torque curve at maximum which is at 2700 RPM. The vacuum gauge will show you that, if you push harder on the gas pedal when the vacuum is at a minimum, you waste gas and it is not good for the motor. I saw what I thought was the perfect mounting in Claude Brousson's GMC at the Las Vegas GMC Motorhomes International Convention (1998). So I ordered a gauge and did the following installation.

The tachometer portion of this meter connects to the TACH connector on the distributor and a second wire to ground. The tachometer will work on either the point ignition or the high energy ignition. They require no power for this function. The vacuum connection is a small rubber tube (provided) from the rear of the meter to a good vacuum source on the motor. This function requires plus twelve volts. The best source of this voltage is also on the distributor at the IGN voltage on the connector next to the TACH connection. The IGN power for the Tachometer only has power while the motor is running. The three conductor cable coming from this meter can end entirely at the distributor on the motor. I found the mounting location shown below to be perfect since the two inch meter will fit between the speedometer and the gauge cluster and the TACHVAC is easy to view through the steering wheel. This mounting requires drilling a 2.125 inch hole in the dash. My 1977 GMC had an existing ½ inch hole that I drilled out to mount the meter.

I am very happy with the finished installation. Watching the gauge is easy while driving and very nice to have both necessary functions on one gauge. The installation was easy except drilling the mounting hole. That required an extension to the hole saw so that I could drill through the spokes of the steering wheel. This was nerve wracking. I used a bushing to reduce the ½ inch hole to the size of the hole saw guide bit and completed the drilling without any problems. I extended the three wire cable supplied with the meter to reach to the distributor where all of the wires terminated.

Materials Required

 TACHVAC is available from:
    Westberg Manufacturing Inc.
3400 Westach Way
Sonoma CA 95476-9709
(707) 938-2121
Part No. E2DC6-23
$197 including tax & freight
 2-1/8 inch hole saw
Three conductor wire cable
Slip-on terminals
Cable ties

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Revised 6/19/98