HEI install - help with 12v power please!

[ViperTed]

I installed a new HEI distributor and found that the "ignition" powered wire I was to use (which measures a full 12v w/key on) drop to .25 volts when I'm cranking the starter. Obviously this won't work. So how do you guys with HEI get a solid 12v power to the dizzy when key is "ON" and in "START"??

I have a '70 with a 351w and was happy to get rid of all that factory wiring. Now if I could only get it to run.%)

NOTE - I heard some guys use a switch between the battery and the dizzy, but I want to keep the dash, etc. as stock as possible. Thanks!

 

[70_Steve]

I installed a new HEI distributor and found that the "ignition" powered wire I was to use (which measures a full 12v w/key on) drop to .25 volts when I'm cranking the starter. Obviously this won't work. So how do you guys with HEI get a solid 12v power to the dizzy when key is "ON" and in "START"??

I have a '70 with a 351w and was happy to get rid of all that factory wiring. Now if I could only get it to run.%)

So, how much of the factory wiring is not there? (and why?)

The stock wiring harness had a resistor wire (ballast resistor) from the ignition switch to the firewall connector. At that connector a wire, from the I terminal on the starter solenoid, was spliced in. That wire continued on to the coil. The resistor wire (ballast resistor) limited the current to the coil when the engine was running. This could be see by measuring less than 12 Vdc at the + terminal of the coil. But, for starting, the I terminal of the solenoid was connected to full 12 volts inside the solenoid, and provided that full 12 volts to the coil for starting.

I don't know what HEI you have, so I don't know what the requirements are for power.

 

[Viperwolf1]

Even with the resistor wire in place the voltage should not drop that low. Sounds like it's hooked up to one of the ACC wires.
Hook it up to the RUN terminal of the switch. If you still have problems starting tie that wire into the "I" terminal of the starter solenoid.

 

[hyghlndr]

Is there any harm of running to the i terminal longterm? I have a custom setup and the keyed switch is hard to get to.

 

[70_Steve]

Is there any harm of running to the i terminal longterm? I have a custom setup and the keyed switch is hard to get to.

The I terminal is only powered from the solenoid when the solenoid is energized. It does get backfed from the resistor wire circuit when the key is in the RUN position. You would not want to power your ignition from the I terminal. -

 

[Viperwolf1]

Is there any harm of running to the i terminal longterm? I have a custom setup and the keyed switch is hard to get to.

No, but it only gets current (and thus 12V) from the solenoid during cranking. The purpose of it is to provide additional current to the coil during cranking when the normal ignition current is lower and going through a resistor wire.

 

[Broncobowsher]

Even with the resistor wire in place the voltage should not drop that low. Sounds like it's hooked up to one of the ACC wires.
Hook it up to the RUN terminal of the switch. If you still have problems starting tie that wire into the "I" terminal of the starter solenoid.

It isn't bad. The run terminal often drops power when in start, but not always. The acc post will drop power when in start.

As mentioned, the I post on the solenoid is a boost that gives full 12V to the ignition during crank. it nullifies the the ballast resistor during crank. So 12V on the run post (in stock form) is irrelevent. As long as it has power in run before the I post drops power it will be seamless.

A beter way of describing the stock wiring is the coil gets fed power from either the ballast wire in run OR the I post during crank. It really doesn't go through one to the other. Just a fork in the road where the 2 merge.

In short, for the original post, add a wire off the I-post of the solenoid to the 12V post on the HEI. Make sure the ballast wire in the harness under the dash is gone. Good to go.

 

[ViperTed]

I had tapped into the threaded stud on the very back of the ignition switch. It tests a full 12v with key in the "ON" position. Now I find that it drops to .25v when cranking. So it sounds like I need to use the wire I have NOW, then additionally run a wire from the "I" post on the starter solenoid? This way the HEI will have full 12v power when cranking AND when running? I would sure prefer to only have one wire running to the HEI, as that's what makes a clean install.

The factory wiring is all there, but after installing the HEI, I removed the original dizzy, coil, and unplugged associated wiring. I'll have to check the voltage on the wires that I unplugged, but I was under the impression they only provided 6v to the original points-type distributor.

70_Steve: Don't all HEI require full 12v? Mine does and I was under the impression they all did.

 

[Broncobowsher]

You got it. You need power from 2 sources. No rule that states the 2 wires must merge at the HEI. You just need the 2 wires to merge and that can then fee the HEI with a single wire.

Steve asks because HEI is either a generic term for eletronic ignition or for a GM based coil in cap, module in base conversion distributor. Most of the time it is the GM stuff being referenced, but from time to time it isn't which is the unknown of your power requirement.

 

[Viperwolf1]

I had tapped into the threaded stud on the very back of the ignition switch. It tests a full 12v with key in the "ON" position. Now I find that it drops to .25v when cranking. So it sounds like I need to use the wire I have NOW, then additionally run a wire from the "I" post on the starter solenoid? This way the HEI will have full 12v power when cranking AND when running? I would sure prefer to only have one wire running to the HEI, as that's what makes a clean install.

That stud terminal is the ACC terminal. If you connect the wire to the RUN terminal it will be hot during cranking also.

 

[Broncobowsher]

That stud terminal is the ACC terminal. If you connect the wire to the RUN terminal it will be hot during cranking also.

The run terminal isn't always hot in start. My last '69 I did the gear reduction starter with the solenoid built in. Ditched the fender solenoid and with it the "I" wire. There were times it wouldn't start. You could tell it was dropping power becasue the gauges (also wired to run) would go off. I really missed the "I" wire keeping the power alive during crank.

Most of the time run was hot in crank, but not always. and I have run across some ignition switches that are always run hot in crank and some that are never run hot in crank. In stock form it is irrelevent.

 

[Viperwolf1]

If the brake warning light works while cranking the run terminal is hot during start.

 

[YNOTBOB2007]

I have a 69. I did what Viperted did and wired mine to the ACC terminal of the ignition, which could explain my hard starting issues. How do I move the wire to the Run position, as the wires are all factory crimped coming out the back of the ignition switch? Do I have to cut the factory wire and splice? Would I be better off adding a wire from the I terminal of the solenoid and splicing that to the wire I installed coming from the ACC terminal to the HEI like broncowowsher suggested? Even though it's an additional wire, I think it may be easier for me than accessing the switch.

 

[Viperwolf1]

I have a 69. I did what Viperted did and wired mine to the ACC terminal of the ignition, which could explain my hard starting issues. How do I move the wire to the Run position, as the wires are all factory crimped coming out the back of the ignition switch? Do I have to cut the factory wire and splice? Would I be better off adding a wire from the I terminal of the solenoid and splicing that to the wire I installed coming from the ACC terminal to the HEI like broncowowsher suggested? Even though it's an additional wire, I think it may be easier for me than accessing the switch.

As I recall the terminals at the ign sw connector are removable but you would have a difficult time finding a new terminal. Best option is to just splice your new wire into the red-green wire near the connector if you don't need the ignition resistor. That should get you max voltage in START and RUN. If it doesn't your ign sw is bad. You only really need to tap into the "I" terminal to bypass the resistor during cranking. Since you aren't pulling current through the resistor, no need to bypass it.

 

[YNOTBOB2007]

o.k. great. To recap: The red/green wire goes to the ballast resistor? And since I don't have one (or has been bypassed by P.O.) I can tap into it at the ignition switch INSTEAD of the ACC terminal off the back, and get full 12V to the dist in Start and Run. I think the way I have it wired now, I'm only getting it in On and not Start, and has been very difficult to start.

 

[Viperwolf1]

o.k. great. To recap: The red/green wire goes to the ballast resistor? And since I don't have one (or has been bypassed by P.O.) I can tap into it at the ignition switch INSTEAD of the ACC terminal off the back, and get full 12V to the dist in Start and Run. I think the way I have it wired now, I'm only getting it in On and not Start, and has been very difficult to start.

Yes. Another plus is the ignition current will be off when the key is in the ACC position. I don't recommend bypassing the resistor if running points though.

 

[YNOTBOB2007]

Thanks Viper. I've been at a loss as to the hard starting issues and thanks to keeping up with this forum, I finally got my answer from someone going through a similar problem.

 

[ViperTed]

Thank you all! When I get a day off, I'll do a lot of wire testing and get it figured out. I have a LOT of wires to check voltage on. I'll let you all know what I find........maybe there's an easy fix, or maybe I'll have to splice the two wires like mentioned above to accomplish my goal.

 

[YNOTBOB2007]

O.K. Had a chance to check voltage at various spots & this is what I came up with. The battery reads 12.5. Drops to 10.6 during cranking. These are the same readings I get from the stud on the back of my ignition switch (the acc stud I believe it's called). I get slightly lower readings on the I terminal of the solenoid. So wouldn't the ignition stud work the best for the single wire going to the HEI? That's how I have it wired now but its been difficult starting. However, since reducing my timing from 12 to 8 degrees yesterday, it's starting better.

 

[Viperwolf1]

The stud terminal is only hot in RUN and ACC. You should use the terminal with the red-green and green-red wires. It's hot in START and RUN, not in ACC.