If you are installing steam gauges, like me, and would like a nice, small round-dial tach, here's an alternative.

I bought a 2 Ė 1/16 inch tach by ISS PRO from Egauges.com. It uses a magnetic pickup so there is no interference with any ignition system.
The gauge comes in three RPM ranges, 4000, 5000 and 6000. It works on 12 or 24 volt. For my Corvair engine, I purchased the 5000 RPM model so that Cruising RPM of 2500-3000 puts the needle in a near vertical position.

They sell for $138.82


Although the text on the web page says it has a red needle, it in fact has a white needle. For aircraft, thatís better as we can put on any red line we desire. It has a slightly convex glass but goes well with other ISS gauges sold by Aircraft Spruce such as the EGT and CHT.

The pickup is a universal magnetic kit. It consists of a coil pickup, two magnets , wire terminals and two part epoxy to glue the magnets on your flywheel, balancer or prop hub.

R8906 Tach Sensor Kit: Universal Tachs - - $59.05


Total price for the tach, sensor and shipping ($16) was $213.91
OKÖ thatís not the cheapest way to go, but it is a quality tach, small size, with simple installation and no calibration required. Just glue on the magnets, wire it up and go.

Shipping was fast. I ordered the tach on a Monday and had it in my hand on Thursday. Of course, you can shop around to find a better price or take my word for it that this is about as good a deal as you will find on this particular tach and sender.

John Pitkin Greenville, TX