Converting coil style ignition to HEI........what is involved?

[NW Task Force]

Hey folks.......... my 57' used to have coil/points distributor with a 235 straight six. The wiring is all "Painless Wiring" and has been since buying it from the previous owner. The little 235 ran good with the painless kit and one wire alternator. Fast forward............. now I have installed a V8 with HEI distributor. What exactly do I need to wire up to the HEI and from where? The old coil wires are marked and I am not sure if these are to be used in wiring up the HEI? Anyone have a good way to wire up the HEI from a coil/points style distributor (diagrams, pics, etc)? Thanks!

[Denee007]

Hi, I can't tell you what your old wires were for, but when I installed a new wiring harness from hotrodwires, one wire was dedicated as the Hot wire to go to the BAT side of the dist cap, the other terminal was for Tach. In essence, a full 12 volt source needs to go to the dist. I suppose your dist will be grounded via the engine and engine to chassis. So with a test light you could locate your hot wire, which should show 12 volts on a VOM.
I'm sure someone with much more knowledge than I will chime in soon; )
Dne'
Posted via Mobile Device

[mr48chev]

Remove the factory resistor as it isn't needed or wanted with the HEI. That wire looks a bit light to use with an HEI though a most of us run at least a ten gage wire to the HEI,

The wire that was running from the neg post on the coil should be for the tach. If you have a tach you will need to change ends on it and run it to the tach pin on the dist cap next to the bat pin. The tach will probably be off though as it was set for a six cylinder. You can usually remove the cup and set the tach to 8 cylinder pretty easily. Most have a 4-6-8 switch on the back side of the tach it's self inside the cup. if it doesn't have a tach just remove that wire.

If the ign wire is hot when the engine is cranking you can just extend it

[NW Task Force]

Originally Posted by mr48chev

Remove the factory resistor as it isn't needed or wanted with the HEI. That wire looks a bit light to use with an HEI though a most of us run at least a ten gage wire to the HEI,

The wire that was running from the neg post on the coil should be for the tach. If you have a tach you will need to change ends on it and run it to the tach pin on the dist cap next to the bat pin. The tach will probably be off though as it was set for a six cylinder. You can usually remove the cup and set the tach to 8 cylinder pretty easily. Most have a 4-6-8 switch on the back side of the tach it's self inside the cup. if it doesn't have a tach just remove that wire.

If the ign wire is hot when the engine is cranking you can just extend it

My truck never had a tach installed in the cab. I am not planning to run one.......so in a "nutshell", the coil Positive wire should just connect to the HEI batt terminal?

[mr48chev]

Originally Posted by NW Task Force

My truck never had a tach installed in the cab. I am not planning to run one.......so in a "nutshell", the coil Positive wire should just connect to the HEI batt terminal?

That wire isn't needed then. I'd follow it to it's other end as it may have been connected to a hidden kill switch at one time if there was no tach in the truck.

Still over the past 60 years the truck has probably been through several owners and had things added, things removed an wires left behind by previous owners. I'm still dealing with the wiring my uncle and his cowboy buddies did on the 71 GMC i inherited from him. The way they wired some things up makes no sense and doesn't work.

[mr48chev]

Can't edit post #3 so I will finish the last paragraph here.

What I started to say is that if the hot wire to the coil /hei still has 12 volts when you are cranking you can just extend it or run a heavier wire in it's place. There are some early style ignition switches that don't run power to the coil when the key is turned to start as they rely on the resistor bypass to carry the power to the coil when the starter is cranking the engine. That is just something to be aware of in the swap. The easy fix would be to run the bypass wire even though it doesn't have a resistor to bypass now.

Some ear

[1project2many]

I like to install a relay on the 12V ignition wire. The key closes the relay which connects the HEI BAT terminal through 10 GA wire to the battery positive post. This allows you to keep your wiring from key to distributor, reduces total current draw through the ignition switch, and isolates the HEI power lead to eliminate engine run-on from reverse current leakage through the alternator.

[Denee007]

oh gosh, does a distributor draw that much current? I'm especially interested in your "run-on" from the alternator! My new engine runs for just tad when I turn the key off, but the man at hotrodwires said it may be from my electric fan that was wired directly. This has been remedied since Dave Chapman put together a relay system, but I haven't started the truck since then. So would that mean most everything that draws significant current should have a relay? like my aftermarket AC system? and maybe even the headlights?
dne'

Originally Posted by 1project2many

I like to install a relay on the 12V ignition wire. The key closes the relay which connects the HEI BAT terminal through 10 GA wire to the battery positive post. This allows you to keep your wiring from key to distributor, reduces total current draw through the ignition switch, and isolates the HEI power lead to eliminate engine run-on from reverse current leakage through the alternator.

[mknittle]

Originally Posted by Denee007

oh gosh, does a distributor draw that much current? I'm especially interested in your "run-on" from the alternator! My new engine runs for just tad when I turn the key off, but the man at hotrodwires said it may be from my electric fan that was wired directly. This has been remedied since Dave Chapman put together a relay system, but I haven't started the truck since then. So would that mean most everything that draws significant current should have a relay? like my aftermarket AC system? and maybe even the headlights?
dne'

No denee the starter robs so much power that the coil won't fire. That is where the extra terminal on the starter solinoid went. so if you ever have an engine that fires just as you let off the switch that wire could be the problem. Or if you have the wires reversed the engine can start but will not shut off.

[OrrieG]

Originally Posted by mknittle

No denee the starter robs so much power that the coil won't fire. That is where the extra terminal on the starter solinoid went. so if you ever have an engine that fires just as you let off the switch that wire could be the problem. Or if you have the wires reversed the engine can start but will not shut off.

6v VW's had the same problem, starter circuit ran all the way to the front switch and back, no juice left to fire the coil. 70's fix was to use a GM horn relay. My wife had really nice calves in the 70's from pushing our van to get it started on hot days in Elpaso and Phoenix until I put in the relay. Now she has nice ones from kicking me in the butt to keep me motivated...

[NW Task Force]

Originally Posted by 1project2many

I like to install a relay on the 12V ignition wire. The key closes the relay which connects the HEI BAT terminal through 10 GA wire to the battery positive post. This allows you to keep your wiring from key to distributor, reduces total current draw through the ignition switch, and isolates the HEI power lead to eliminate engine run-on from reverse current leakage through the alternator.

Sounds like a good thing to do. Wondering if anyone has a wiring picture or diagram to show this. Prints/pictures really help me visualize the setup. Thanks!

[Denee007]

Yes, and make sure your block is grounded to the chassis which will give a good ground to your distributor. You want full 12 volts at your HEI batt terminal. ; )

[1project2many]

My truck never had a tach installed in the cab.

There aren't many reasons to have a wire from coil- running into the cab. In a points ignition like our trucks had, the coil- connects directly to the distributor. If the added wire isn't for a tachometer or RPM measuring device, there's a very good chance it's for an aftermarket electronic ignition. You should follow that wire and see what's at the other end.

Relay wiring is fairly simple.

         /
Bat+    /
--------     o-------------- HEI BAT+ Terminal
        )()()(
Ign    |      |
From   |      |
Sw-----        --------Ground

When the switch is on, ignition current routed through the coil of the relay to ground (terminals 85 and 86) closes the relay and allows current to flow from battery to the HEI (terminals 30 and 87).

HTH

[Denee007]

But as mr48 chev says, you may want to upgrade your wiring leading to your dist. Mine is a pretty heavy wire, but it goes through my ignition switch which eventually possibly shorten the life of the ignition switch. With your original setup of points and condenser, a little wire did the trick, but with an HEI, it's hungry for 12 volts so a full 12 volts is needed to give you the full advantage of an ass kicking spark at the plug. ; )
So back to the relay idea! Dave chapman can help you out there! He's an expert at relays and makes them.
Posted via Mobile Device

[4544speed]

I would check www.painless.com if the truck aready has a wiring harness from painless. I installed one 10 years ago and my wires are individually labled. If you can find the part number for the kit they have PDF manuals on line. Many times, with the newer wiring, the wire sizing is designed for an HEI. That depends on the kit and the age. You may not need the relay. Mine has not had one in all these years. If I was unsure I would add the relay. The painless folks are great to deal with and will probably answer your question if you call them. The following is from my painless manual. I have never had any problems with the wiring or kit and I don't have relay. Disclaimer : I am not implying anybody else is incorrect and I am not an expert.

7.3.4 If you are using a Ballast Resistor, mount it away
from other wiring or hoses. The Ballast Resistor gets
very hot during operation. Connect ENGINE
SECTION A wire #920 (pnk) to one end of the Ballast
Resistor. Connect the other end of the Ballast Resistor
to the Ignition Coil B+ terminal with 14-gauge wire
(you may have enough pink wire left over to
accomplish this). If you are not using a Ballast
Resistor, connect wire #920 directly to the Ignition
Coil B+ terminal.
Note: The ballast resistor has been deleted from
this kit due to lack of consumer usage. If one is
needed in your application, please call Painless
Performance at 800-423-9696 for assistance.
Important Note! For HEI systems route wire
#920 (pnk) to the Distributor and attach it to
the terminal labeled BAT. No Ballast Resistor
is required.

[1project2many]

oh gosh, does a distributor draw that much current? I'm especially interested in your "run-on" from the alternator! My new engine runs for just tad when I turn the key off, but the man at hotrodwires said it may be from my electric fan that was wired directly. This has been remedied since Dave Chapman put together a relay system, but I haven't started the truck since then. So would that mean most everything that draws significant current should have a relay? like my aftermarket AC system? and maybe even the headlights?
dne'

The average current draw isn't large for HEI. But for a short time, each time the coil begins to charge, they draw a lot of current. It's called "instantaneous current draw" and it's the real reason why GM used such a large wire for HEI systems. Plenty of people have learned by experience that too small a wire diameter can cause problems with the way the truck runs.

If you had wired an electric fan directly to ignition power then the truck probably continued to run for a second or two after the key was switched off. The cooling fan motor instantly turns into a generator when you stop applying power and since there was no relay or switch, that small generator was able to supply power to the ignition system for a short period to keep it running. I'm sure Dave's relays will take care of it. Another problem that crops up is when a truck is converted to alternator. The SI style alternators in original form require a small voltage supply that's tied into the ignition wire. The factory uses a resistor or runs this wire through the ALT light to cut down on current but many people just wire it to a key on power wire during a conversion. When the key is shut off a small voltage can be supplied from this wire back into the ignition system. Some ignitions only need to see a few volts on the ign+ line to stay powered up so this setup won't shut off with the key. The relay isolates the ignition so it can't get power.

The old truck ignition switch was designed for a bit of current. Turn signals, ignition, heater fan, maybe a cigar lighter, and a tube radio might have added up to 30 or so amps. But I wouldn't subject an old switch to that kind of current draw. An underdash AC with condenser and fan can draw 10-20A alone. The electric cooling fan is probably another 15A. Any lights or other devices added to the ignition circuit only serve to route more power through your switch. A better answer if you expect to have high current draw may be to use a large relay to power a bus bar or fuse panel and tie all your circuits to that.

Headlights and brake lights are powered by battery power which doesn't go through the ign switch. But if you're planning to go with Halogen or high power lights you'll find they're brighter if you use larger wire than original. You could install relays out near the lights and get the same effect by supplying battery power through them but it seems like unnecessary complexity. Still, it may be easier than replacing all the wiring.

[Denee007]

1project2many, great answer! I'll get with Dave Chapman~ he's the man for relay systems~; )

NW task Force, I hope you got an answer you were seeking, and hope you get your truck up and running soon! Sometimes, a simple question winds up being lengthy and confusing! Your question posed questions for my project as well, I thought I was covered! Apparently not~ once my truck is together up and running, I do not want to go back and have to fix things! There is no manual for what we do, only our common sense and cool people on this forum to help us. ; )
dne'

[NW Task Force]

Originally Posted by Denee007

NW task Force, I hope you got an answer you were seeking, and hope you get your truck up and running soon! Sometimes, a simple question winds up being lengthy and confusing! Your question posed questions for my project as well, I thought I was covered! Apparently not~ once my truck is together up and running, I do not want to go back and have to fix things! There is no manual for what we do, only our common sense and cool people on this forum to help us. ; )
dne'

Thank You!!! Yes, many of the responses helped me out on where to start and how to go about getting it wired up properly. All of my wires on the truck are in good condition (painless wiring kit), however, some painless wiring labels have fallen off. The kit was installed by the previous owner back in the early 90's. I think Painless Wiring was fairly new to the scene during that time??? Not sure. Anyway, I cannot tell you how bad I want to have my truck running in the coming months. My wedding is in July and I really want to drive away in it with my new bride. Here is a sneek peek of it in the garage (current pic)..................

[Denee007]

Lets take some of this over to my build thread, I don't want to clutter up NW TaskForces thread with my questions. Mcknittle, come over to my thread please; )
Posted via Mobile Device

[Denee007]

Well first off a big congratulations on your upcoming marriage, and may you your bride to be blessed for a wonderful life together; ). Your truck is gorgeous! Stay at it, you'll get it going!!
Dne'

What is your name please? I feel funny calling you NW task Force; )
Posted via Mobile Device

[NW Task Force]

Originally Posted by Denee007

What is your name please? I feel funny calling you NW task Force; )
Posted via Mobile Device

My name is Chris. Thank you for the great comments. My fiance' is very excited and has been pushing me to work on the truck. Sadly, this truck has not been on the road in over 13 years! The truck was driven regularly to cruise nights and car shows in the local area before being torn apart for modern upgrades. The truck was originally a father-son project that went totally cold. I joined the military and moved away and the truck just sat & sat at my parents house. Fast forward.........the truck was turned over to me and now I have a garage of my own to get it done and a reasonable budget to help fund it. I'm really anxious to get it going.

[Denee007]

Without having to go back through your thread,

WHAT DO YOU HAVE LEFT TO DO TO GET IT GOING??

[NW Task Force]

Originally Posted by Denee007

Without having to go back through your thread,

WHAT DO YOU HAVE LEFT TO DO TO GET IT GOING??

I still need to set the final pinion angle for the rear axle and have a driveline built. Other things are fairly small.......run a section of fuel line to the engine, wire up the HEI & ignition switch. Finally, install the radiator and electric fan. I have all the parts I need sitting in the garage......just need to get them on.

[Denee007]

hm, kind of like a Honey do list! Maybe make a calender up to the day you have to have the truck ready, and make sure you have everything done for your part in jumping over the broomstick. Make quality time to work on the truck maximizing your plan of action to make this truck ya'll's chariot! THen a quick test drive! and there you have it!

[NW Task Force]

Getting my HEI all wired up soon............. where are most people running the battery + wire from the HEI to? I realize it has to be a constant 12V power supply? Should I run a stand alone wire from the HEI to the postive battery post or down to the positive post on the starter? Just wanna make sure I'm doing this correctly so the circuit is not overloaded amperage wise. Thanks