Tachs and Magnetos - last question before I go in the garage

[Travis]

Buddy is asking my more than my poor brain cell can handle... He is running a Vertex Magneto... what tachs will work? Can he use the old style EB-9A/Sun tachs?? Anything else? What about a rev-limiter setup?

Travis

[yorgatron]

i might be wrong but you might need a mechanical tach for that.

[BigJim394]

He can use one of the old half moon type Sun Tachs that require the sending unit, but the EB-9A won't work with the Vertex. They made three of them expressly for the Vertex mag, and the one for 8 cyl. engines is the EB37A. Hard to find but not impossible.

[draggin'GTO]

I was running a Vertex mag on a VW drag car some years back. I bought an electric Auto Meter tach for it that was made especially for a mag.

----- Bart -----

[cornfieldrodder]

If he has a cable drive on the Vertex a mechanical tach will work just fine. most are calibrated to work at 1/2 crank speed...camshaft speed!! Therefore a Yamaha or Honda bike tach would work in a pinch. Autometer has a tach especially for this application. PM me and I'll give you a price for one of mine, I'll probably never use "em again anyway. A couple of companies, including Autometer sell or have sold an inductive tach with a pickup that goes over one spark plug wire. Those tachs will work on any ignition you have that fires on the compression stroke only.

[Roothawg]

Here's the problem. They don't make a mechanical tach anymore. I called Autometer and they told me I would have to buy a magneto signal convertor which I did. Although it might be some of my trouble with the car banging out at 5500. I think we have that fixed but if it starts acting up ...that's the first thing I am disconnecting.

Call Joe Hunt....they supposeably have a convertor that screws into the side of the mag tach drive. Hope this helps.

[BigJim394]

This diagram:

http://www.egauges.com/pdf/ATM_Tips/vrtxmag.gifhttp://www.egauges.com/ATM_Tips.asp?TipPage=green_wire.htm</a>

[cornfieldrodder]

Autometer has not made a mechanical tach since before I worked for them in the early 80s. Moroso may still have them as well as Ford.

[four-thirteen]

SW still makes a mechanical tach. speedway number 665D535AH. I've got the older model of the same version in my '62 plymouth, which I race, and really like the tach. Way better than the electronic auto meter gauge. This one has a good skinny needle which makes it easy to see the readout. It anit no cheap piece of chrome plasic, it's a real instrument, built like they should be. If I had a choice for all my cars, they would all have a mechanical SW tach.

I've got a NOS sun half sweep in my model A(no tach drive on the mag). It's the one without the sender. The directions say that certain models connect directly to the mag terminal, -12v, and ground. Mine isn't one intended for use with the mag, but I misread the directions and hooked it up anyway. The damn thing works. Seems they would be the same, as the potential difference in the mag terminal is fluctuates from about +12v to 0v, just like it does on a points ignition. I don't know if it reads right, as it is the only way I have of measuring rpm on the motor.

If I can figure out the workings of the old sun tachs, I could probalbly use a few transistors to build an adapter driven off the vertex. I'm going to school to be an electrical engineer... Dave

[greaseball]

Travis!
What happened last Wednesday...?
Still interested in the truck?
http://www.jalopyjournal.com/ubbthreads/images/graemlins/confused.gif