also interested, doing same conversion on 72.
Converting to HEI.. electrical question
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 1,132
Likes: 0
Converting to HEI.. electrical question
So, I bought a tach drive HEI from the group purchase and am wondering how to power this thing up.
I have a 71 corvette with the old style points distributor. The wiring harness is original, which means I have two wires that connect to my coil in one location, and on the other side of the coil, a wire runs from the points distributor to the coil. The new distributor that I got has a place to plug in a power wire... problem is that I have no plug on my original wiring harness - it's just two wires that converge into one with a hook on the end to screw down on the coil. Is there anyway I can buy this plug at an auto parts store; and if so, what would I have to do with the wires?
Thanks,
Michael
I have a 71 corvette with the old style points distributor. The wiring harness is original, which means I have two wires that connect to my coil in one location, and on the other side of the coil, a wire runs from the points distributor to the coil. The new distributor that I got has a place to plug in a power wire... problem is that I have no plug on my original wiring harness - it's just two wires that converge into one with a hook on the end to screw down on the coil. Is there anyway I can buy this plug at an auto parts store; and if so, what would I have to do with the wires?
Thanks,
Michael
Safety Car
Joined: Feb 2006
Posts: 4,367
Likes: 59
From: FL
Most HEI distributors require a full 12 volts. Your points system uses much less at the coil. So you have to follow the wiring back to the ballast resistor on the firewall and connect to the full +12 volts on the other end.
The two wires connected together you will need to tape up so they do not short to anything. One comes from the starter solenoid and is hot when you have the key in the Start position, the other carries 3 to 8 volts from the ressistor.
I'm not sure if the wiring to the +12 volt side of the resistor is heavy enough to carry the current you need. Some who have done this should know.
I've only used HEIs in cars that we modified the wiring on, also, and were not trying for a stock look.
The two wires connected together you will need to tape up so they do not short to anything. One comes from the starter solenoid and is hot when you have the key in the Start position, the other carries 3 to 8 volts from the ressistor.
I'm not sure if the wiring to the +12 volt side of the resistor is heavy enough to carry the current you need. Some who have done this should know.
I've only used HEIs in cars that we modified the wiring on, also, and were not trying for a stock look.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
All Hei run anywhere from 10v to 17 volts.
As Mark_Milner said find thefull 12 volt feed before the ballast resister (if there is no ballast resister then you have a resistance wire)
Tap into that wire (I prefer to solder) where it is a full 12 volts with the key in the "run position". The wire is big enough #14. You can just tape all three wires together at this point and just not use the 2 originals. In case you ever want to swap back and forth. Test the new wire for a full 12 volts in both the start and run positions.
You can get the connector pigtail at a parts store.
As Mark_Milner said find thefull 12 volt feed before the ballast resister (if there is no ballast resister then you have a resistance wire)
Tap into that wire (I prefer to solder) where it is a full 12 volts with the key in the "run position". The wire is big enough #14. You can just tape all three wires together at this point and just not use the 2 originals. In case you ever want to swap back and forth. Test the new wire for a full 12 volts in both the start and run positions.
You can get the connector pigtail at a parts store.
Drifting
Joined: Jan 2006
Posts: 1,944
Likes: 22
From: Yooperville MI
You can purchase the power connector from Summitt or a complete kit with connector and several feet of wire from MAD. http://www.madelectrical.com/
The best power source is to splice into the pink wire at the ignition switch. This is how they were wired in production. The MAD kit comes with a 10 ga wire that you can route through your firewall to the switch. Your original positive coil wire is a resistance wire, and will eventually fail if you try to power the HEI with it. Tape up or heat shrink the ends of both of your old coil wires and wrap them into the harness.
The best power source is to splice into the pink wire at the ignition switch. This is how they were wired in production. The MAD kit comes with a 10 ga wire that you can route through your firewall to the switch. Your original positive coil wire is a resistance wire, and will eventually fail if you try to power the HEI with it. Tape up or heat shrink the ends of both of your old coil wires and wrap them into the harness.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Most of the Gm wiring harness have the "ballast resistor" built in. The resistor is actually a length of wire that has a spec'd resistance and not the ceramic block like most people think.
If you don't want to cut your original harness, run a 10ga wire to an "IGN unfused" terminal in the fuse block.
If you don't want to cut your original harness, run a 10ga wire to an "IGN unfused" terminal in the fuse block.
Instructor
Joined: Dec 2006
Posts: 190
Likes: 0
From: Henderson Ky
you don't have to touch your original harness. tuck your original wires neatly out of the way and run a wire directly from your fuse panel to the power terminal on your cap. make sure you find a source on the panel that is keyed hot. you can buy new plug ins, you could go to any junk yard and cut one off any gm car with hei or you can use the blue female connector from any automotive electrical kit.
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From: Henderson Ky
Racer
Joined: Apr 2006
Posts: 450
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From: Alexandria Va
While doing some research for my own HEI conversion, a friend sent me this link. In no manner am I saying the information is accurate. enjoy.
http://www.oldengine.org/unfaq/hei.htm
http://www.oldengine.org/unfaq/hei.htm