Friday, March 26, 2010

Counting the Revolutions

In February I finally received my new, reproduction Smiths Tachometer. It's styled after the classic gauges with new electronic internals. The Gauge Guys (APT Instruments) supplied the unit straight from the fine folks over at Caerbont in the UK. I had a chance to correspond with with one of the employees over there when we were having some communication issues and I was really impressed, thanks Neil! Thanks also to Chuck over at Gauge Guys for getting this arranged from this side of the globe.

I think mine is a fairly standard 8,000 RPM unit, although I requested the rounded chrome bezel to match my existing gauges.

In the picture above you can see the boxed Tach and my gauge pod that I ordered up. The pod itself fits any 80mm instrument and comes in a semi-gloss black finish. However, you can see from the picture above that I opted to repaint it in a wrinkle-finish black. I really dig the wrinkle finish. I'll be painting more with this later.

The pod was slightly modified beyond the finish and of course I didn't photograph it. So I'll try to describe what was done: I had one of the guys at work open the slot that allows the angle adjustment so that it could sit parallel to the mounting surface. From the factory they're set up to do about 15°, which wasn't going to work for what I had in mind. Of course what I had in mind didn't work out anyway so it probably would have been fine the way it was set up.

I can't say I was that impressed with the pod itself. It looks like the tooling they use to press these out is either very tired or rather crude. However, once dressed in the snappy wrinkle finish all gripes are forgotten.

Figuring out how I wanted to mount this worked out a lot better in my head than it did in practice. For instance, I learned very quickly that there is no real estate on the steering column large enough to accommodate the pod. Since that was the whole reason for modifying the tilt angle in the first place, I was a bit disappointed. I rallied when I decided to mount it on the lip of the dash shelf (one day I'll learn the technical term for this structure).

Getting this here ended up being a lot more challenging than I would have thought. Once again, my solution went un-photographed so I will list what I had to do to achieve this final positioning.
  1. Removed the metal trim.
  2. Pulled the dash pad away from the support structure.
  3. Drilled a 1/4" hole in the top of the support.
  4. Applied primer to the hole to prevent rust.
  5. Installed mounting hardware (see illustration below).

My illustration is definitely not to scale, but the dash structure curves away from the point where I drilled the hole which would have made it impossible for the washer to remain perpendicular to the bolt. So I modified the nylon spacer and added the chamfered edge on one side so that the metal washer would sit flat when everything was tightened down. The results were good and the mounting is rather sturdy now.

It was necessary that I clip out a portion of the chrome trim so that the fender washer on top could clear without interference and the nylon washer below could do the same. I wasn't really thrilled with doing this, but once everything was installed it doesn't show. Which is good, because it wasn't pretty.

Lesson #2: During the course of a restoration it will become increasingly important to learn how to work metal so that not every effort is a hack job. So make a point of learning some solid methods and buy the appropriate tools.

The wiring for this was relatively easy, but for the cramped quarters inside the cabin. Although there are six wires in the harness only four would be used for my application.
  1. Green: 12v switched power - I added an inline fuse holder from NAPA to my green lead and connected this to White wire off starter switch.
  2. Black: ground - connected to Black wire from auxiliary lighting harness.
  3. Red/White: dash lamp power - connected to auxiliary lighting lighted switch power.
  4. Red/Blue: negative side of the ignition coil.
I have a Pertronix Ignitor and Flamethower II coil. The Ignitor unit did not have a tachometer output so the negative side of the coil was the best bet. Once again I had to pass a wire through the dash and the pile of plumbers putty used to seal that off. As far as a sealing method, it works fairly well, but it can be a royal pain trying pass a wire through.

The tach has the classic perimeter lighting that is consistent with my stock cluster. It's a really warm, analog look that I think is missed in modern cars today with their digital clusters.

Wrapping Up
One thing I had not considered by placing the tach where I did was how I would get the dash pocket support back in. This turned out to be a major pain as it was necessary to disconnect the Windscreen heater vent so that I could shimmy the platform in behind the gauge. I also struggled a bit trying to get the wires routed where I wanted them to go. These are all challenges that I will revisit when the interior is revised in the future. I hope I can find some better ways of dealing with them at that time.

I really like the placement; it's in a great position as far as visibility goes.

If I had one complaint it would be that the needle action is a little too digital. Where my speedometer bounces like an analog gauge will, the tachometer tends toward a very precise movement. Of course this just means that it's a lot easier to read. So I guess that's a win for modern mechanicals.

Here's a quick video I took with the phone to show it in action. As you watch one thing I'll point out is that at start up it appears to do a quick self test. So it briefly puts the needle below zero and then starts displaying the RPM. I should say that's my hope at least, as opposed to this being some signal that something has gone completely pear shaped as far as my wiring goes.

Next up will likely be the fuel system. I want to replace the 5.5 gallon tank that I currently have with a 9 gallon unit. Even though the Mini gets decent gas mileage, five gallons doesn't really deliver on the range. I also want to look at replacing any worn components along the way.


  1. hello, I try to mount the tachometer on my mini morris, could you give me the wiring diagram? thanks for your help.

  2. About time I put mine in, mad revival of an old post but, do you have any pictures of your nylon spacer??