HEI wiring questions

[cjoenny89]

Ok I am installing a new starter tonight and I started reading on that and it posed some questions on my HEI I have it wireed with the old yellow wire from the original dist. It has 12v on it but I am having warm starting issues. I read I should wire a new wire to the HEI? Does that yellow wire lose voltage during cranking? Is that a possible a problem why I am having trouble starting hot? On a side note my yellow wire was broke off at the starter. Should I wire it back up tknight when I put on the new starter and does it matter what side the solenoid coil the purple and yellow wire go?

[geezer#99]

Purple wire on the inside terminal. With hei you don't use the yellow wire or the resistance wire it's attached to. Run a seperate 12 gauge wire from an unfused barb on your fuse box.

[Stocker]

Originally Posted by geezer#99

With hei you don't use the yellow wire or the resistance wire it's attached to. Run a seperate 12 gauge wire from an unfused barb on your fuse box.

x2

[LockDoc]

-
x3 and I'll include a picture. Connect a wire from here to the BATT terminal on the HEI....

LockDoc

[VetteVet]

See the cloth covered wire in the middle, It is the resistance wire that goes to the coil and starter yellow wire. You can take it out of the block and install a 12 gauge red wire and run that directly to the distributor. It runs straight to the key switch ignition terminal in the cab.

[davepl]

Originally Posted by cjoenny89

It has 12v on it

Electricity doesn't work that way - it'll always have a full 12V on it, no matter how much resistance, so long as its not under load. You could have a 10000000 ohm resistor the size of a coffee can, and so long as current can flow, it'll be 12V with no load on it.

You'd have to measure the resistance of the wire (or check the voltage under some significant load).

All the other stuff up there is spot on - I just wanted to remind people that you can't identify whether or not a wire has resistance based on no-load voltage.

[cjoenny89]

I wired it to the bat terminal on the HEI and to the fused ignition terminal on the fuse block.
Is that going to work?
How did that affect my HEI having it wired to the yellow wire?
Would it not make the truck run good or possible hard to start when warm?

[LongBox]

With the yellow wire, the HEI will not get full voltage when the truck is operating.

[cjoenny89]

Might explain all the timing issues I have been fighting

[Andy4639]

When it was hooked to the old coil it had to drop down to about 9 volts while you cranked the truck.

With the HEI you want full 12 volts while it cranks. If you use the yellow wire as it was installed it want crank when hot as you talk about. The wire could have 12 volts are as little as 9 volts on it at any other time. Yes it can cause timing issues also.

VV has the main deal and is correct with taking the fuse block loose and swapping it out.

[cjoenny89]

thanks for all the help and the pictures! when I get the starter in I hope to give a update!
Chad

[geezer#99]

Originally Posted by Andy4639

When it was hooked to the old coil it had to drop down to about 9 volts while you cranked the truck.

With the HEI you want full 12 volts while it cranks. If you use the yellow wire as it was installed it want crank when hot as you talk about. The wire could have 12 volts are as little as 9 volts on it at any other time. Yes it can cause timing issues also.

VV has the main deal and is correct with taking the fuse block loose and swapping it out.

That's backwards Andy!!
The yellow wire supplied 12v to the coil only while starting via the starter solenoid. Then cut back to 8-9v thru the resistor wire to keep the coil from overheating and dieing..

[davepl]

Originally Posted by LongBox

With the yellow wire, the HEI will not get full voltage when the truck is operating.

The feed from the fusebox to the coil, which is the resistor wire, is a white fabric-covered white.

The feed from the solenoid to the coil, which is only active during cranking, is yellow.

When you upgrade to HEI, the white wire goes away and is replaced with a non-resistor wire (ideally in red). The yellow wire can then stay, as it does no harm, but serves no purpose, so I generally remove it.

[Andy4639]

Originally Posted by geezer#99

That's backwards Andy!!
The yellow wire supplied 12v to the coil only while starting via the starter solenoid. Then cut back to 8-9v thru the resistor wire to keep the coil from overheating and dieing..

Correct sorry I was typing to fast I guess. I should have proof read it before posting.

[71CHEVYSHORTBED402]

Long ago "my mechanic" hooked up a kill switch to the small receptacle behind the power wire at the HEI. Very cool idea. Only problem is he routed that and the HEI power wire through the speedometer hole in the F/W. Those and a 10 AWG ground wire, and a 10 AWG positive to a fuse box on the RH fender. I haven't traced those yet, but it should be interesting and they're definitely a pair. Whatever they are they're gone.

Unless someone has a better solution, seems both wires for the HEI, or at least the power wire can run through the hole where the orange wire in woven sheath "should" be, which is for Transmission Controlled Spark. Word is you're better off without the TCS.

[cjoenny89]

ok let me get this straight I ran a wire from the fused ignition terminal through the firewall to the Bat terminal on the HEI.
Are you telling me I can splice into the white cloth sheathed wire on the firewall and go to the Bat terminal on the HEI?
Which is a better way to go?

If I stay with how I wired it up do I need to cut or remove any of the original wiring? I taped off the ends of the yellow wire that was originally on the starter and the yellow wire that went to the DIST.

Does this white cloth sheathed wire need to be removed from the system?

If it is as simple as tying into the white wire on the firewall I could cut it and solder it a splice on there and run it to the HEI. Maybe I am not understanding this white wire yellow wire!

[geezer#99]

Leave it like you have it.
Tape the yellow wire ends into the wire bundle and leave it all there. It hurts nothing and it'll still be there if you ever decide to put the points distributor back in.
Some people prefer to remove the resistor wire at the firewall junction box and install a new wire from there with the required male wire spade that clips into the box. You need to seperate the two halves of the junction box to do that. Not a fun job. You don't want to be soldering on that junction box. You could create other wiring problems.

Here's a thread on replacing the white wire.
http://67-72chevytrucks.com/vboard/s...ght=hei+wiring

[LockDoc]

Originally Posted by cjoenny89

ok let me get this straight I ran a wire from the fused ignition terminal through the firewall to the Bat terminal on the HEI.
Are you telling me I can splice into the white cloth sheathed wire on the firewall and go to the Bat terminal on the HEI?
Which is a better way to go?

If I stay with how I wired it up do I need to cut or remove any of the original wiring? I taped off the ends of the yellow wire that was originally on the starter and the yellow wire that went to the DIST.

Does this white cloth sheathed wire need to be removed from the system?

If it is as simple as tying into the white wire on the firewall I could cut it and solder it a splice on there and run it to the HEI. Maybe I am not understanding this white wire yellow wire!

Do you mean the UNFUSED ignition terminal? I don't think you would want the HEI +12v wire fused.

The resistance wire is a special alloy single strand wire. (it may be stainless) It is very tough and doesn't cut or solder well. It will be hot any time the ignition is in the "on" position. I would remove it as VettVet suggested if you want to use that terminal for your HEI. I think the wire inside the firewall that connects to that terminal and goes to the ignition switch is a regular wire, not a resistance wire.

LockDoc

[cjoenny89]

thanks I will do my best to look at removing it

[t76turbo]

Have any of you tested voltage drop at the IGN Unfused terminal while starting???

The PO on my truck used the white cloth wire just to go through the firewall but connected regular wire under the dash and from the engine bay side of the firewall connector to the HEI distributor. That worked fine on the stock style HEI that had a capacitor under the cap but my new MSD Billet HEI must be more sensitive and complained. Basically it wouldn't start when we first tried to fire up my new 454.

Long story short we found that even when measuring at the terminal itself the voltage still dropped significantly while starting. I had to run a relay with battery power to get it to start.

[Stocker]

Originally Posted by t76turbo

Have any of you tested voltage drop at the IGN Unfused terminal while starting???

No, I have not..... but the truck starts (& runs) well with the HEI powered by that lug. It's been there since sometime in the 1980s. I suspect it's a reliable power source.

[Sturvin]

The best way to do it is to run a relay to your HEI. The old ignition cylinders are not rated for the 30A bursts that HEI will draw. They will work for a while then one day they will burn out without warning.

Ideally:

Cloth wrapped (or better yet re-pin that terminal with a normal 10-16 AWG wire) to the "trigger" of the relay.
Ground wire to the relay.
Battery voltage (through a 10 AWG wire) to the relay.
Then a 10 AWG wire to the HEI from the relay.

This lets your ignition only see the small amperage required to trip the relay, yet run a stable 12v @ 30A to the HEI.

Pertronix makes a kit that has really nice instructions:
https://www.summitracing.com/parts/pnx-2001

[RichardJ]

This is intended for those that think running a wire into the fuse box is some kind of electrical breakthrough.
I took the electrical diagram that is in the electrical section and very crudely erased all wiring that is not part of the ignition or charging circuits. I just used the eraser in Windows paint.
I see the forum software reduced the size so you will have to enlarge it with your browser or save it somewhere and enlarge it there.


The Red 12R wire from the Battery, connects to the Alt and to the firewall connector. The 12R on the other side of the firewall connector feeds the Ignition switch, but also splits off and feeds the part of the fuse box that is hot at all times.
The 12V goes into the Ign on the 12R and when the switch is ON, it comes back out on the 12P (Pink). The 12P feeds the back half of the firewall connector, but also branches off to feed the part of the fuse box that is hot with key ON.
The 12P feeds the 20W/OR/PPL on the other side of the firewall connector. 20W/OR/PPL is the cloth covered Nickel, resistance wire that everyone is so afraid of.

The 12P wire that connects the 12volts from the Ignition switch to the firewall connector IS the most direct route for anyone to use for connecting the HEI.

By-passing the firewall connector and connecting to the fuse box is the long way around and actually probably adds resistance to the circuit because of extra connections within the fuse box and extra wire.

The stock GM HEI draws about 2 Amps. The MSD stock type coil in cap HEI draws about 8 Amps. The DUI HEI equivalent draws 7.2 Amps.

The HEI is a great distributor, but there is no reason to get crazy about the wiring. GM wired it with 14 gauge wire. They used 14 G with extra thick insulation so don't let that confuse you.

[Sturvin]

Most of the time , yes it does draw a more reasonable sub 10 amp load. However, it momentarily jumps up to 30A and due to the small contacts, that are probably dirty and worn in the ignition cylinder, it can burn them out. Unless you have a high end multi meter, you won't see it because it does not update fast enough.

Vehicles that came stock with HEI have an ignition switch that is built to handle these current draw. That is why they do not run a relay on factory gm HEI.

[cjoenny89]

thanks guys I did rewire it to the fuse box but since then I ordered the
year one electronics HEI wire harness for 67-72 trucks, now I wish I would have waited I really like the relay idea but I can still use the HEI wire harness I bought and use the relay later. I will say that the truck ran so much better this way!
I also changed out my battery because I noticed I only had 11.96 volts at the battery and 11.46 volts at the HEI. I put good interstate in it and now I have 12.96 at the battery and 12.46 at the HEI. I also replaced the old starter with a new one what a difference in cranking between the battery and starter!
I will tell you at 60mph down the road the engine runs way better with the HEI wired up this way. I know I need to adjust the timing yet because it still starts a little hard but it will start now after driving it 20 miles. I drove around then picked my son up at football.
It rolls over slow then speeds up like it is going to start then slows down for a few cranks then speeds up and fires right up. could it be the timing? If I turn the dist. CW it cranks easier. I will put a timing light on it Friday. what is the proper timing for a 327 with a mild cam in it? I am not sure of the specifics this engine was rebuilt in 1988 by my dad and older brother then it sat until 2015 so I was 14 or so when he did the engine and didn't care much back then.
any help on timing for advance settings would be grateful!
here is a pic of the truck it has been many years coming and long hours by myseld getting it going to take my dad for a ride who is now 82! This was his dads truck bought new in 1968.