[Fried_Guy]

I had a points ignition and a tach installed and working properly. Now I have an HEI distributor and the same tach. Whenever the tach is hooked up to the "tach" terminal on the distributor, the car won't start at all. As soon as I disconnect it, it works fine. I've checked the grounds and everything works properly. Do I need a new tach? Some kind of HEI adapter or something? Do I need to wire something differently (I have the IGN source from the fuse box hooked up to the BAT side of the distributor)? Please help me out here!

 

[m22chevy]

Your tach should work fine with the HEI dist. Sounds to me like your wire from the tach is grounding the HEI coil some how or possibly you don't have 12 volts at the bat terminal on the HEI! Do you have full 12 volts going to the distributor?? You must eliminate the resistor that the points type distributor used and run a full 12 volt wire to the bat terminal on the HEI. Will the engine stall if you hook the tach wire up after it's running?? HEI distributors only needs that one 12 volt source to run!
Mike, M22

 

[Fried_Guy]

I don't have the resistor wire any more, and I THINK that it's a full 12 volts. I'm runnint a 14 guage wire from the IGN porn on the fuse box. That's 12 volts, right?

 

[John_Muha]

I don't see it offhand. Tend to agree with M22Chevy. The only thing is you said the tach used to work fine. Perhaps something odd with the coil. Missing the ground strap? Though that doesn't make really good sense, I threw it out anyway. If no other ideas come up, I'd borrow a cap and coil and see what happens.

 

[Fried_Guy]

Update: I tried to attach the tach to the distributor while it was running and it sparked and the distributor "slowed down". The car didn't die right away. It kind of stuttered. If I left it on too long the engine would stop. If I took it off and it wasn't on too long, the engine ran fine. Am I not getting a full 12 volts to the distributor? I'll check it with a voltage tester. Any help would be appreciated. Thanks guys.

 

[Fried_Guy]

Problem Solved:

I got the old voltage tester out and started checking the connections on the tach. The BAT term was fine at 12 volts exactly. The TACH term was fine when grounded to the manifold at almost 12 volts. But when I connected the TACH term to the TACH wire on the tachometer I noticed a drop of about .35 volts. I tested the voltage of the TACH wire then and found it to be .35 volts. I was back-feeding down the tach wire. I took all the wiring out my tach and re-wired it. Now it works great.