The Stovebolt Site Forums The Shop Area The Electrical Bay what do i need to know to buy a tachometer?

I have a hei inline 250 motor in my '49. The distributor has a wire connection for a tach, but I need to know what tach will work with what I have. I just want a simple little 3" tach- nothing special, but never delt with this before. Thanks for the help!
Jeremy

If you're buying new,pretty much any tach should work fine for you. I have a a Faria tach in my '74 Chevy truck that only works with a V-8,and a couple of 1980's (?) SunPro tachs I'm using on my older trucks;they're adjustable for a 4,6 or 8 cylinder engine,will work with points or HEI ignition. Don't know if they work on six volts (I remember seeing that mentioned on one of the truck forums recently), or how to set up for positive ground,but SunPro's Tech line people could likely answer that for you. These tachs sell for 50-60 bucks at most parts stores.
Speed

I didn't know if I should be looking for tach with a certain amount of hookup wires (kinda like a 1 or 3 wire alternator), mechanical or electric, how many cylinders or if they're all compatable.

If you're running a 12 volt, negative ground electrical system, you've got a bunch of options. Original 6-volt systems, or any system with positive ground narrows the field a bunch. Check out the JEGS catalog, or possibly PAW, and you'll find a wide variety of designs and prices.

Just pick one that fits the mounting position you want, and be sure it has a 4-6-8 cylinder selection capability. Most tachs will have at least 4 wires, (+) and (-) power connections, a trigger lead that goes to the distributor, and a wire that attaches to the dash light circuit for illumination. Some of the high-end tachs will include circuitry for rev limiters, shift lights, etc. Unless you're racing, those features aren't necessary.
Jerry

Can use SunPro or others on 6v system with voltage booster.
The bigger the face the better the resolution, stay away from the small dia tach.
Denny Graham
Sandwich, IL

okay thanks guys! The truck is a 12 volt system so that should make it easier.

Gnd, hot wire, signal wire from the dist. That's all there is to it if your 12v.
Denny G

Denny, why do you say stay away from the small diameter tach?

"Cause if you're half blind like me..........
Ya can't see the buggers!

Go the Monster 5" Tach like me and not only does it block half your view.......the bloody shift light blinds you at night!

Go for what fits your interior and eyesight best.

Circumference Big, the larger the circumference the better defined or higher the resolution of the scale. On the 2” face it is very difficult to read closer than a couple hundred rpm, bump that up to a 3”or 4” face and now you can accurately read with in 50 rpm. I suppose the easiest way to explain what I mean is with a picture. Try this: http://rides.webshots.com/photo/2513482700098611668dGaxvt
Which one would you rather try to read while bouncing around at 55mph?
Denny Graham
Sandwich, IL

Makes sense. I just thought your eyes were going bad.

HI....I was hoping that somebody(s) with a 235 and HEI would chime in and let us know which brand, part number, and from where they purchased their tach. A lot of us want a tach but there are so many choices and which ones (types) will work well in our trucks? Hope to hear from some of you and T/C Steve