Tach Problems

I hooked up and old suntune tach my dad gave me today. The problem is it does not register any rpms at idle. When I hit the gas it does register though if it is correct I am not sure. Is there a difference between points and electronic ignition tachs? I have an electronic ignition in my 75. Thanks...

 

I found that my Auto Meter, wouldn't work with my Pertronix. My tach is about 20+ years old.

 

Would I be better of getting a newer one? Mine is really old also.

 

Is it possible that the ground needs to be better. I need to hook up other gauges and do not have a power source. How can I add a circuit to my fuse box?

 

I had to put a ballast resistor inline with the tach signal, sounds goofy, but it worked.

 

Expansion Fuse Block

I just installed one of these. http://www.summitracing.com/parts/PRF-70107/ It provides both switched (ignition on) and constant on circuits with a relay to energize the switched circuits. I used the resistor wire for the points distributor to switch the relay. I'll use two switched circuits for the electric choke and 12V electronic ignition. Constant on circuits will power the horn relay, maybe electric fan, and maybe headlights thru a relay. Lots of options.

 

I am running the msd blaster 3 coil. Does this make any kind of difference?