HEI hot wire connection voltage question.
Race Director
Joined: Sep 2004
Posts: 11,874
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
from the google search" All the system needs is an ignition switch controlled 12 volt source that is live in both the "crank" and "run" positions. To wire the system, the ballast resistor wire feeding the points-type coil needs to be removed and replaced with regular copper wire. This is because the points system used this resistor to reduce the voltage to the coil to around 9 volts while the switch is in the "run" position to prevent the points from burning up too fast. The coil on the points system is also supplied by a "bypass" wire from the starter solenoid. This wire bypasses the resistor wire to compensate for the voltage drop caused by the starter motor during cranking. The HEI system needs the full battery voltage at all times to work its best. One common hookup method is to replace the ballast resistor wire with a normal copper wire and attach both wires to the power input terminal. This ensures the HEI receives power both during cranking and running.
what this means is that the HEI uses what ever the battery voltage is during cranking and also during the normal engine operation and the range on a normal car goes from 9v to 14v. the old cars points systems were designed around the cranking voltage of 9 volts and thats why they had the bypass and ballast resistance circuit systems.
for reference put your voltmeter across you battery while cranking you will never get more voltage then what you are reading there.
what this means is that the HEI uses what ever the battery voltage is during cranking and also during the normal engine operation and the range on a normal car goes from 9v to 14v. the old cars points systems were designed around the cranking voltage of 9 volts and thats why they had the bypass and ballast resistance circuit systems.
for reference put your voltmeter across you battery while cranking you will never get more voltage then what you are reading there.
Last edited by bobs77vet; Nov 19, 2012 at 11:23 AM.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
I am not arguing that the HEI works the same at 6v vs 13.6v just that at normal cranking voltage there is enough juice to fire the coil and create a spark to jump the car to life.
measure the voltage across your battery when you are cranking, if you have that at the HEI while cranking then you have the most voltage you are ever going to get.
fyi
http://www.popularmechanics.com/cars...stions/4221215
measure the voltage across your battery when you are cranking, if you have that at the HEI while cranking then you have the most voltage you are ever going to get.
fyi
http://www.popularmechanics.com/cars...stions/4221215
Last edited by bobs77vet; Nov 19, 2012 at 12:25 PM.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
good luck twinray on fixing your problem. oldalaskaman and I seem to have a difference of opinion. you know my thoughts good luck bob
Racer
Joined: Apr 2012
Posts: 464
Likes: 1
From: Austell Georgia
Check your voltage at the battery when cranking. Do not rely on the gauge. 9v is a little low when cranking....enough for an HEI but more of a drop than you should see with a healthy system and a large enough battery. WHat size battery CA do you have?
You mention it was working fine before but now its hard starting. Have you changed anything on the car since it started fine or is the only variable temperature
You mention it was working fine before but now its hard starting. Have you changed anything on the car since it started fine or is the only variable temperature
Le Mans Master
Joined: Aug 2010
Posts: 9,272
Likes: 17
not really an argument, I've put the chevy hei on everything , toyotas, mercedes ,volvos, suburu's,fords, and on and on . for my money its the best system available and user friendly. you can glue a chevy hei module to a fender and run an ignition system with it, it will work , and for awhile on reduced voltage, but not very well and not for long.
hope this helps
http://www.google.com/url?sa=t&rct=j...ETWaX1VQPEjyKg
I havent been linking or spouting any of my own opinions but only whats available as tech. on the web.
hope this helps
http://www.google.com/url?sa=t&rct=j...ETWaX1VQPEjyKg
I havent been linking or spouting any of my own opinions but only whats available as tech. on the web.
Race Director
Joined: Nov 2006
Posts: 19,445
Likes: 353
From: Athens GA
St. Jude Donor '12-'13, '15- '16-'17-'18-'19, '21
I would also look for other reasons for the voltage drop.
How old is the starter, the battery, etc......????
An old battery under load will drop off below 12v.
And an old starter will drain more juice also.
If it was running fine with the HEI setup and new ignition wire, I would not consider the HEI as the source of the problem.
My $.02.
Good luck and let us know what the final result is.
Bman
How old is the starter, the battery, etc......????
An old battery under load will drop off below 12v.
And an old starter will drain more juice also.
If it was running fine with the HEI setup and new ignition wire, I would not consider the HEI as the source of the problem.
My $.02.
Good luck and let us know what the final result is.
Bman
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Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
I have my HEI powered from an unused switched wire connector from the fuse panel. It gives full 12v+ reading when the ignition is turned on. It drops to 9V when it goes to crank mode. Is this OK or is there a better connection that will give a full 12V reading when the starter is cranked? I've developed a hard cold start condition now that the temp has dropped and am wondering if this is the reason why. Thanks
A battery that will deliver 100% at 90° can deliver 30% less at 32°.
That is why the resister wire was bypassed on points systems and why all batteries have a cold cranking amps rating. Battery chemical reactons just slow down the colder it gets.
Always make sure all you cable connections are good, but in your case check the spark at the sparkplug, then the carb for fuel issues (choke).
Most new vehicles use relays for almost everything including the ignition. If you tested the hei power feed to show less than battery voltage then a relay is good insurance.
Safety Car
Joined: Oct 2000
Posts: 3,593
Likes: 103
From: Southern Indiana
Im pretty sure a HEI has to have 12 volts all the time, thats why you can't use the old pink resistence points wire that drops voltage while cranking and the runs 9 volts normal.
In HEI anything less than 12 volts will result in a weak spark.
In HEI anything less than 12 volts will result in a weak spark.
Tech Contributor
Joined: Jun 2004
Posts: 20,910
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
That's not how a points ignition system or the HEI works. Please review post #8 or the Ignition sticky. The sticky has been up quite a while, and some of these posted myths should have been discarded by now.
Thread Starter
Melting Slicks
Joined: Aug 2005
Posts: 2,683
Likes: 34
From: Working on the car NY
I would also look for other reasons for the voltage drop.
How old is the starter, the battery, etc......????
An old battery under load will drop off below 12v.
And an old starter will drain more juice also.
If it was running fine with the HEI setup and new ignition wire, I would not consider the HEI as the source of the problem.
My $.02.
Good luck and let us know what the final result is.
Bman
How old is the starter, the battery, etc......????
An old battery under load will drop off below 12v.
And an old starter will drain more juice also.
If it was running fine with the HEI setup and new ignition wire, I would not consider the HEI as the source of the problem.
My $.02.
Good luck and let us know what the final result is.
Bman
Being I'm not too electrically minded
, I changed the connection to that from the horn relay. It did product a higher cranking voltage (maybe 10) than from the fuse box connection I had but 
when I shut the ignition key off, the car kept running since it wasn't a switched lead
. It didn't fire up immediately from that anyway. I'm still working on it and also my wipers which 
don't work either - but that's another story.In additon, the wire from the fuse box is connected to a plug in connector from the fusebox. I'm wondering if the plug is set up as "resistance" which is why I have 8-9 Volts when cranking. As mentioned, I'm running a 12G wire from the plug, so Voltage loss should be minor - maybe I'll try 10G.
Last edited by TWINRAY; Nov 20, 2012 at 10:34 AM.
Thread Starter
Melting Slicks
Joined: Aug 2005
Posts: 2,683
Likes: 34
From: Working on the car NY
At the battery when cranking is wayy more than at the HEI distributor connection point. When cranking, the battery is 11V+ (maybe even 12v). Battery voltage "sitting" is 13.2V+.
Last edited by TWINRAY; Nov 20, 2012 at 10:39 AM.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Thread Starter
Melting Slicks
Joined: Aug 2005
Posts: 2,683
Likes: 34
From: Working on the car NY
. Happy Thanksgiving to all.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
Start with a fully charger battery or have the charger still connected.
Using a multimeter, test each component of the system all the way to the HEI 12v feed connector with the key on. Use the battery post itself not the cable end. Failures include, all cables, switches and connection points. A 0.4 voltage drop at any one test point is a problem per GM service manual.
In short, if the battery post has 11.0v, then the horn post should ideally have the same whether sitting or cranking, always the SAME.
12ga is adequate for the hei (although bigger is always better
).
Nowhere on the fuse box should you have less than battery voltage, even past the original resistance wire with the coil disconnected.
It is prudent to just take the time to remove and clean all of your wire connections from and including the battery clamps all the way to your problem areas. Include the ground cables and their connection points. An easy way is to dip them in a baking soda solution and use. I use copper antiseize to protect from oxidation. Or you can use thios stuff that Ferrari uses
http://shop.advanceautoparts.com/web...=30-88120749-2
Starting off this way will make your troubleshooting a lot easier.
Using a relay for the hei power feed is a nice modern way to wire it, but not necessary at all.
Using a multimeter, test each component of the system all the way to the HEI 12v feed connector with the key on. Use the battery post itself not the cable end. Failures include, all cables, switches and connection points. A 0.4 voltage drop at any one test point is a problem per GM service manual.
In short, if the battery post has 11.0v, then the horn post should ideally have the same whether sitting or cranking, always the SAME.
12ga is adequate for the hei (although bigger is always better
).Nowhere on the fuse box should you have less than battery voltage, even past the original resistance wire with the coil disconnected.
It is prudent to just take the time to remove and clean all of your wire connections from and including the battery clamps all the way to your problem areas. Include the ground cables and their connection points. An easy way is to dip them in a baking soda solution and use. I use copper antiseize to protect from oxidation. Or you can use thios stuff that Ferrari uses
http://shop.advanceautoparts.com/web...=30-88120749-2
Starting off this way will make your troubleshooting a lot easier.
Using a relay for the hei power feed is a nice modern way to wire it, but not necessary at all.
Thread Starter
Melting Slicks
Joined: Aug 2005
Posts: 2,683
Likes: 34
From: Working on the car NY
I don't think the hard cold starting is voltage related. Today, I changed the float to what was in my Q jet before I did my "performance" upgrade. It is still a "small" float but was in my Qjet when I had the oem motor in it. I did the carb rebuild then in 2002 and the carb ran great with the oem motor till I parked it in 8/2008 when I 
started my resto. I didn't have time to put the carb back on the car today- something aout 
Thanksgiving at the brother-in-laws . I'll put the carb back on the car tomorrow and see how the cold starting is.l
started my resto. I didn't have time to put the carb back on the car today- something aout Thanksgiving at the brother-in-laws . I'll put the carb back on the car tomorrow and see how the cold starting is.l
Safety Car
Joined: Oct 2000
Posts: 3,593
Likes: 103
From: Southern Indiana
Thats why you have to run a new wire from a switched 12volt source from the fuse block out to the HEI power lug.
Points can't run at 12 volts or they will burn up.
Last edited by Tim H; Nov 23, 2012 at 09:00 AM.
Racer
Joined: Sep 2009
Posts: 437
Likes: 3
From: Alvin Texas
Ign. wiring; the resistor wire is bypassed when the switch is turned to start and power to the dist is supplied through the started solenoid to the dist. (This is in points system).
On these systems when converting to HEI I pull the resistor wire at the bulkhead connecter and replace it with new 14 ga wire and terminals. I then run a new 14 ga wire from the solenoid ign terminal to the new terminal at the dist B+ . (You could use the factory wiring for this but a 14 ga is better). This gives a hot batt voltage at start and a batt voltage during run. All wire terminals soldered.
On these systems when converting to HEI I pull the resistor wire at the bulkhead connecter and replace it with new 14 ga wire and terminals. I then run a new 14 ga wire from the solenoid ign terminal to the new terminal at the dist B+ . (You could use the factory wiring for this but a 14 ga is better). This gives a hot batt voltage at start and a batt voltage during run. All wire terminals soldered.
Last edited by bpassmore; Nov 23, 2012 at 11:05 AM.