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post #1 of (permalink) Old 12-27-1999, 08:41 PM
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Super Coil or HEI... What\'s the difference

I got an unexpected Xmas present from my Pop... an ACCEL High Performance Super Coil. He had been listening to me talk about doing the GM HEI conversion on my 84 CJ7 258, and decided to surprise me with the coil (along with some 8mm spark plug wires to handle the increased load). According to the catalog, this coil pumps out 45,000 volts.

What is the difference between installing this Super Coil and doing the GM HEI conversion? Don't both just boost voltage in the ignition system, so that it will burn fuel more efficiently, improve performance, improve gas mileage, etc.?

If the coil provides the same benefits, why bother with the extra time and expense of the GM HEI?

Thanks in advance!

<font color=green> Go easy! You're talkin' to a greenhorn. </font color=green>
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post #2 of (permalink) Old 12-27-1999, 11:09 PM
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Re: Super Coil or HEI... What\'s the difference

Why bother with the GM coil?! Its the thrill of the hunt, the fun of sticking something never intended for your Jeep into it's engine and having it work really well. And they are big and look cool too! Thats kinda like saying "Why bother re-grooving your old street tires into mud-lugs when you can just BUY some MTs from the shop 5 mins away?" Sure, you COULD do that...but then you can't have tires that leave an imprint of your name in the dirt (NOTE: these are bad tires to use if you wheel on private property without permission)

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post #3 of (permalink) Old 12-28-1999, 12:44 AM
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Re: Super Coil or HEI... What\'s the difference

[img]/wwwthreads_images/icons/smile.gif[/img] That Accel coil combined with an electronic trigger in the distributor(no points) will be a comparable combination to a GM HEI.....just more difficult to find a coil if that one quits.[img]/wwwthreads_images/icons/crazy.gif[/img]

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post #4 of (permalink) Old 12-28-1999, 11:33 AM
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Re: Super Coil or HEI... What\'s the difference

Actully, there is a lot more too it than that. The main reason the HEI works so well is because its bypassing the compter on the timing. The Duraspark system works in conjuction with the computer to constantly adjust the timing to keep the emissions correct. If you look at the system you will see that the dist signal goes to the control module. Based on inputs from the computer the control module will vary the timing...that is how the knock sensor can cause the timing to be retarded. By adding the HEI, you are bypassing the computer and performing about the same task as the Nutter bypass.

Truth be known...Coil voltage is way over rated...the only time it really matters is on really cold engines and under heavy load...the higher the compression, the more energy it takes for the spark to jump to the electrode. A hotter spark will not increase power. Once the air/fuel mixture burns....what does make a difference is the timing of that needs to happen at just the right moment...too soon, pre-ignition...too late, poor power. All these factors also contribute to emissions.

The beauty of the HEI is that its a very simple and compact design with a very repeatable advance curve. It does a very good job of producing a short hot spark at just the right moment. This is actually the same thing the Jacobs systems do....but for more $$.

Bottom line....The Accel coil may help it run a little better if you have some marginal plugs or wires and if you live in one of those frozen states. Otherwise, I bet you won't see any difference.......Do the HEI.

John......southern CA
84CJ7,3"lift,32"BFG,4.11's,ARB,Solid Axle's
post #5 of (permalink) Old 12-28-1999, 12:20 PM
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Re: Super Coil or HEI... What\'s the difference

I'm kinda like you. I've been thinking about some new Accel stuff for my 81 CJ-7 258. When you install your Xmas presents, please post the results.
Good Jeepin, Larry

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post #6 of (permalink) Old 12-28-1999, 12:34 PM
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Re: Super Coil or HEI... What\'s the difference

I'm in complete agreement with DDawg. The additional energy of the coil is only as good as the distributor it has to flow through to get to the spark plug. The Duraspark distributor is a good distributor, but a lot of that energy will be lost going through it and it is nowhere near as accurate as the HEI. This is why racers don't just replace their coil when they are looking for a hotter spark. They replace the whole ignition system - coil, distributor, wires, and plugs. The reason we all recommend the HEI rather than let's say the MSD 6A system is parts availability, like CJDave said. Are you going to be able to find a rotor for a MSD distributor in Silverton, Colorado when you break down in Yankee Boy Basin? Probably not, but I'll bet they have one for the HEI. Remember, a chain is only as strong as its weakest link.

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