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  #1  
Old 01-22-2006, 12:20 AM
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JAKE266 JAKE266 is offline
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Default Confusion Over HEI Coil Wire Colors

I have an 86 Corvette with a stock HEI distributor. I want to replace the ignition coil but am confused as to which one to buy because of the difference in the colors of the coil wires.

My Corvette manuals says if my pickup coil has a yellow lead, then the ignition coil MUST also have a yellow lead. When I checked the wire colors on my pickup coil one is green and the other "Looks" like a faded yellow, but it's hard to be sure since the distributor is 20 years old.

Yet when I check for the available coils, red and white wires are shown for the Vette of my year. Even AutoZone and other auto parts stores show red and white and the correct coil wire colors.I check MSDs offering and it has red and yellow wires, but I couldn't find which cars it's meant for.

ALSO, can you explain just what the difference is between HEI coils with red and white leads and ones with red and yellow. I've asked around on other forums and no one seems to have a convincing explanation.

What could I expect to happen if I installed a coil with the INCORRECT wire colors?

Thanks,

Jake
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  #2  
Old 01-22-2006, 11:34 AM
bill jones bill jones is offline
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-as far as I know the ignition coils (not talking about the magnetic trigger coils) for the older HEI coils (non-ecm controlled) have a red wire which is the coil positive and connects to the keyed 12vdc power and to one side of the module.
-the other wire which is commonly a white color is the coil negative and connects to the other side of the module--and is where conventional tachometers are connected to.
-Typically these red and white coils are for 8 cylinder applications
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-The red and yellow wired coils always seemed to be on 4 cylinder and 6 cylinder engines.
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-I have run the red and yellows on 8 cylinder engines and I see where they produce a better spark and use more slighty amperage like when wanting to improve a stock HEI for performance.
-I've never had a problem because of using a red/yellow coil in place of of red/white coil---but I have never wasted any time replacing red/yellow coil with a red/white coil because I never saw any gain in that swap.
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-I have mostly worked on the older HEI's but I have never seen a yellow wire on a magnetic trigger coil---all I've ever seen is a green and a white.
-There is however an orientation of those to wires that relates to rotational direction of the rotor where cw rotational such as a Chevy has the white on the right and CCW rotation like a Pontiac or Oldsmobile has the white on the left.
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-If you car is ECM controlled then I doubt what I said here means anything that will help you.
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  #3  
Old 01-23-2006, 09:43 AM
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JAKE266 JAKE266 is offline
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Thank you for your response.

Yes, I'm confused as well and have been for a while now just trying to get to the bottom of this wire color difference thing.

My distributor IS ECM controlled; It has no advance weights and no vacuum advance. All the timing is controlled by the ECM and the data burned into the PROM.

Without re-burning the PROM, the only control I have over ignition timing is the setting the initial advance, which, in the case of my 86 Vette, is 6 degrees BTDC.

As I'm sure you already know, the SBC rotates clock-wise 18436572 and from the coil installation instructions I've seen, the red wire connects to the B+ BAT location and the white or yellow to the C- TACH location.

I'm hoping to get a final resolution to this because I really DO want to install a new coil; mine's approaching 20 years old so I figure it's about time.

I've found only ONE MSD, in-cap, HEI coil. I'm just not sure if it'll work with my ignition system or, even worse, it'll work initially only to fail on me sometime down the road which will probably leave me stranded in the boonies.

Thanks again,

Jake
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  #4  
Old 01-23-2006, 10:41 AM
msdtechsupport1
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The color of the wires will not have any affect on the operation of the coil itself. Our PN 8225 will work just fine for your application.
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  #5  
Old 01-24-2006, 11:02 AM
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JAKE266 JAKE266 is offline
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Quote:
Originally Posted by msdtechsupport1
The color of the wires will not have any affect on the operation of the coil itself. Our PN 8225 will work just fine for your application.

Thank you for that information. That removes the confusion I'd been experiencing when looking at the other coils available, specifically from one of your competitors - ACCEL - which offers TWO versions - coils with red and white wires and coils with red and yellow wires.

So from your info, using MSD's coil doesn't require any consideration of the wire colors of the pick-up coil.

Guys on the Corvette Forum - Forums.CorvetteForum.com - will be happy to read what you posted since this issue comes up often.

Thanks again,

Jake
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  #6  
Old 01-24-2006, 03:24 PM
msdtechsupport1
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Not sure why Accel has two versions. Something to do with air conditioning??? They could probably answer that for you.
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