Matt,
I am relunctant to chime in here since there is so much conversation by people who seem to know what they are talking about. I don't want to add to the confusion.

I have a '73 with an MSD HEI, an MSD blaster coil, MSD HEI pointless tach drive distributor. MSD specifically states that you need to hook up the MSD box directly to a 12v battery source. Don't borrow power from another circuit. The threaded stud on the horn relay, driver's side fender area on the '73 is 12v battery hot all the time and I used that as my 12v battery source. Everything seems to work fine if the rest of the wiring is hooked up per the instructions.

 

Any way you could snap a picture of that setup?

 

Crafty, if you use the battery hot all the time connection, you won't be able to turn off the engine. The reason yours is not starting is because you hooked up to the original resistance wire. The easiest solution is to run a new 12 gage wire from the batt connection on the hei to the fuse box and plug into the connection marked IGN. That will give you full voltage and it should start and shut off correctly.

 

the answer to your question is in earlier post but i will chime in anyway. there r several ways to fix this. run a new wire through the dash to the fuse box to the ing terminal on the fuse box and your done. if your like me and do not enjoy running a wire thru the fire wall and under the dash then i would recommend using the existing wire your using now( the 6 volt restistor wire, original wire). buy a 5 dollar relay from autozone and use the resistor wire to trigger it. it takes like a half amp (quessing here) to trigger it so plenty of power. then you run a dedicated wire from the battery or starter connection to the relay and a new ground to the engine block. then all you have to do is run a wire from the relay to your hei. full power, and no going thru the dash. which ever works best for you.

 

since i provided an answer, i feel a small thread hijacking is ok

what hei distributor r you using with the mechanical tach. like a 1971 ls 5?

 

Sure I can snap a pic for you. My cars starts and turns off just fine. The MSD owners manual does say that sometimes (rarely), power can be fed to the MSD box through the gen light when the car is turned off and cause the car to continue to run. A simple filter (1 amp 400v diode) came in the kit to prevent this from happening but I didn't need it.



Here are a few exerpts from my MSD owners manual:

HEAVY RED WIRE - This wire connects directly to the battery positive (+) terminal or to a positive battery junction or the positive side of the starter solenoid. Note: Never connect the alternator. I used the threaded post on the horn relay under the hood.

ENGINE RUN-ON
Here is what CF member '75 is talking about. I didn't have this problem:

If your engine continues to run even when the ignition is turned Off you are experiencing engine Run-On. This usually only occurs on older vehicles with an external voltage regulator. Because the MSD receives power directly from the battery, it does not require much current
to keep the unit energized. If you are experiencing run-on, it is due to a small amount of voltage going through the charging lamp indicator and feeding the small Red wire even if the key is turned off.
Early Ford and GM: To solve the Run-On problem, a Diode is supplied with the MSD in the parts bag. By installing this Diode in-line of the wire that goes to the Charging indicator, the voltage is kept from entering the MSD. Figure 6 shows the proper installation for early Ford
and GM vehicles.
Noteiodes are used to allow voltage to flow only one way. Make sure the Diode (it's a common 1 amp 400 volt diode) is installed facing the proper direction (as shown in Figure 6).
Ford: Install the Diode inline to the wire going to the #1 terminal.
GM: Install the Diode in-line to the wire going to terminal #4.
GM 1973 - 1983 with Delcotron Alternators: GM Delcotron Alternators use an internal voltage regulator. Install the Diode in-line on the smallest wire exiting the alternator (Figure 6). It is usually a Brown wire.

 

don't think i would want power to the hei all the time. cain't be good for it.

 

That's what MSD recommends. The box is internally fused as well.

 

This poster didn't mention MSD, so I thought he was talking about a regular HEI, the wiring for them is different.

 

 

Hijack away! this is some good info that everyone can use. I think we have just about every type covered

 

not sure i can go back to a points system after going hei 8 years ago. lol just did not know how to handle the mechanical tach thing. i think i had to hammer massage my 67 small block camaro to clear the fire wall.

 

While having any non clock/ECM part powered up all the time seems like a waste of current and battery life, I don't think you'll hurt the HEI module. It only uses milliwatts of power while it's in a "standby" mode (not switching an inductive coil).

 

Well I ended up going with an HEI wiring kit and a relay kit from MAD. I talked to Mark who is the owner, and he also thinks that the problem is that the resister wire is being used to power the HEI. When I get the kit I am sure I will have more questions. Thanks for the help so far!

Matt