'68 HEI Conversion
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Racer
Joined: Jun 2005
Posts: 409
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From: Lavonia Georgia
'68 HEI Conversion
I picked up a tach drive HEI for my '68 327. Need to run a switched 12V to the HEI. I've heard of just stripping back the stock coil wire until you find the end of the resistor section. Then you cut off the resistor part and splice in a new piece of plain copper. Is this the best/easiest way or is there anything else you recommend? I put in the MSD hop up kit with 50kv coil and I want to ensure the wire is up to the task.
Thread Starter
Racer
Joined: Jun 2005
Posts: 409
Likes: 13
From: Lavonia Georgia
HEI Power Wire
Originally Posted by big_G
I would run a dedicated wire to the fuse block. Look for ignition power (IGN) connection. Also for security, you can add a cut-off switch in series to ward off the thieves. 
Tech Contributor
Joined: Jun 2004
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by big_G
I would run a dedicated wire to the fuse block. Look for ignition power (IGN) connection. Also for security, you can add a cut-off switch in series to ward off the thieves.
Drifting
Joined: Jan 2006
Posts: 1,944
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From: Yooperville MI
The pink wire on the ignition switch is the best power source, that's what GM used on HEI cars. Contact MAD, he has a kit with the correct wire and the distributor connectors for about $20. I have converted several points type cars to HEI with no problem. http://www.madelectrical.com/
Thread Starter
Racer
Joined: Jun 2005
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From: Lavonia Georgia
Originally Posted by ahoover
The pink wire on the ignition switch is the best power source, that's what GM used on HEI cars. Contact MAD, he has a kit with the correct wire and the distributor connectors for about $20. I have converted several points type cars to HEI with no problem. http://www.madelectrical.com/
I thought about running some #10 wire fused at the battery terminal to a hidden switch inside somewhere, then on to the HEI. That way, I have lots of uninterrupted power to the dist, and a little bit of extra safety from theft. If I do that, what size fuse should I use? I want enough to power the dist, but not so much it would fry something if it ever somehow shorts.
Le Mans Master
Joined: Sep 2001
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From: Unreconstructed, South Carolina
Originally Posted by 68vertible
I thought about running some #10 wire fused at the battery terminal to a hidden switch inside somewhere, then on to the HEI.
Thread Starter
Racer
Joined: Jun 2005
Posts: 409
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From: Lavonia Georgia
Originally Posted by jackson
The first time you forget to cut power to distributor ... and walk away ... you will probably damage the HEI module/coil ... and may be walking again.
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Burning Brakes
Joined: Dec 2004
Posts: 1,020
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From: Nederland Texas
As I've been looking into changing my 68' non-tilt/tele column for a later model that you can actually buy a blinker part for... 
IIt was very easy to locate the wires mentioned above. I also used the same IGN wire to power my new Aeromotive fuel pump. They are a half-moon shaped plug-in connection on the steering column located midway down. Very easy...turn the key on and test for power.
IIt was very easy to locate the wires mentioned above. I also used the same IGN wire to power my new Aeromotive fuel pump. They are a half-moon shaped plug-in connection on the steering column located midway down. Very easy...turn the key on and test for power.
Team Owner
Joined: Jul 2004
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From: Redondo Beach, California
You need a wire that is switched on to 12 volts when the ignition key is turned. Some people have said that the yellow (?) wire going to the windshield wiper motor can be used to power the HEI.
Can someone substantiate this.. or state that this is not correct? Thanks
Can someone substantiate this.. or state that this is not correct? Thanks
Tech Contributor
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by jackson
The first time you forget to cut power to distributor ... and walk away ... you will probably damage the HEI module/coil ... and may be walking again.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
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From: Unreconstructed, South Carolina
Originally Posted by 69427
Unless I am misunderstanding your comments here, I respectfully disagree with both. If you don't cut off power to the HEI a carbureted engine will keep running (assuming the coil C+ itself is not shut off in some sort of way). If you somehow shut off power only to the coil (to kill the engine), the HEI module should still be fine. The power dissipation in this non-normal mode is minimal compared to its normal power dissipation when it is controlling the coil primary current.
It is not uncommon for production HEI cars to have ignition damaged because the driver left the key in "ON" position ... to power up the cig lighter ... or didn't use the "ACC" for radio ... it does happen.
Tech Contributor
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by jackson
Under "normal" conditions ... you're "usually" right ... BUT here's where I respectfully disagree ... let's imagine you get in car w/ HEI wired direct to battery main through an anti-theft switch ... and power up with INTENT to start ... BUT just before you twist the starter key ... you realize your neighbor is flagging you down to tell you about his kid's baseball win... you get out of car and then get sidetracked on something else ... all the while the ignition is HOT because you forgot to power down.
It is not uncommon for production HEI cars to have ignition damaged because the driver left the key in "ON" position ... to power up the cig lighter ... or didn't use the "ACC" for radio ... it does happen.
It is not uncommon for production HEI cars to have ignition damaged because the driver left the key in "ON" position ... to power up the cig lighter ... or didn't use the "ACC" for radio ... it does happen.
Thread Starter
Racer
Joined: Jun 2005
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From: Lavonia Georgia
I'll call MSD to see what they say
You all make great points. I gutted the dist and put in the MSD hop up kit (coil, rotor, Hi-perf module, cap) so I may just call MSD tech support tomorrow to see how they recommend wiring it. I suspect this will not be the first time they've been asked this question. I'll post their answer.
I'd still like to wire it directly because coming up with a 12V source which which is on during cranking and also on when the key goes to run takes me back to simply cutting out the resistor wire and putting in plain copper. I can do this, but I'm just not convinced of the current carrying capacity of that circuit and want to ensure the hi-perf coil and module have plenty of juice.
I'd still like to wire it directly because coming up with a 12V source which which is on during cranking and also on when the key goes to run takes me back to simply cutting out the resistor wire and putting in plain copper. I can do this, but I'm just not convinced of the current carrying capacity of that circuit and want to ensure the hi-perf coil and module have plenty of juice.
Thread Starter
Racer
Joined: Jun 2005
Posts: 409
Likes: 13
From: Lavonia Georgia
Talked to MSD....glad I did
I talked with an MSD tech this morning and he had a great suggestion. You can use the stock resistive wire to pick a high current relay. You wire the original resistive wire to the + side of the relay coil and then put my security switch on the ground side. This way, you can turn off the switch and the relay will never pick, keeping the car from starting and providing that little extra security I was looking for. Then I can run my HEI current carrying wire directly from a fused link at the battery to the relay contact points, then on to the HEI distributor. MSD makes a 30 amp relay (p/n 8861) specifically for this application, or he said any of the quality (Bosch or others) relays which are available for headlight control at Napa/Autozone will work as long as they are capable of at least 30 amps.
This gives the best of all worlds. Uses the stock wiring to trigger the ignition, gives a point to insert the security switch, and provides a high current path to satisfy the HEI.
I think I've got a plan! Thanks again for all the input.
This gives the best of all worlds. Uses the stock wiring to trigger the ignition, gives a point to insert the security switch, and provides a high current path to satisfy the HEI.
I think I've got a plan! Thanks again for all the input.
