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Unread 11-13-2012, 10:05 PM   #1
347jeep
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TFI - HEI conversion

Hello, new to the forum.

Anyhow, I am in the middle of the conversion and I am noticing that the TFI coil is set up to take a connector on the pos and neg terminals and the connector that I can get at NAPA is set up with what I believe to be 16 gauge wires.

My conversion will use 10 gauge and I am under the impression that this is virtually a must for the HEI. So, how do I use the TFI coil and it's connector with a heavy gauge wire such as 10 gauge?

Secondly, I will have TWO wires going to coil positive and TWO wires going to coil negative. How would I make these connections to the TFI coil's positive and negative posts?

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Unread 11-14-2012, 08:37 AM   #2
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Are you doing TFI or HEI? They are not the same. TFI is the large Ford cap and rotor on the stock distributor and the coil used with Ford engines with the TFI ignition system. HEI uses the General Motors HEI distributor. The recommendation for AWG10 for HEI is specific to the GM HEI distributor with the coil built into the cap. You're not using this distributor if you're using a TFI coil.
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Unread 11-14-2012, 08:59 AM   #3
gosupes
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I think he is using the HEI only as an ignition module, the rest are the Ford components. If you have 2 wires going to the positive coil terminal, this is switched power so figure out what else is tapping into that power source but it's probably from the starter relay. For the 2 wires to the neg coil terminal, this is the signal from the ignition module and there should only be a single wire from the neg coil terminal to the ignition module.

Here is a basic write up with some pics, probably from someone on this board as I recognize some of John Strenk's pictures as well as Jeephammer's. Similar to what I run, I didn't worry about the coil connector and used 12awg wire (what I had laying around) and soldered on female spade terminals to connect with the coil. Been reliable for last 6+ years.

http://www.fairpoint.net/~julienjim/...ion%5B1%5D.pdf
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1986 CJ7, 4.2 w/4.0 head, TFI-HEI hybrid ignition, Clifford manifold w/Holley 390 w/cold air intake, OBA, 4.5" lift, Woody CV shaft and Tattons in front, 4.10 gears - lunchbox in front, Truetrac in the back, twin-sticked, blower upgrade for running topless, trying to keep it simple.

It's just a Jeep, and if you don't wheel it once in a while, it's not even that.
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Unread 11-14-2012, 01:16 PM   #4
86cj74.2L
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Quote:
Originally Posted by gosupes
Here is a basic write up with some pics, probably from someone on this board as I recognize some of John Strenk's pictures as well as Jeephammer's. Similar to what I run, I didn't worry about the coil connector and used 12awg wire (what I had laying around) and soldered on female spade terminals to connect with the coil. Been reliable for last 6+ years.

http://www.fairpoint.net/~julienjim/...ion%5B1%5D.pdf
Are you using the e-core ford coil and a stock duraspark ICM and its lasted 6+ years. If so I'm very impressed.

Also TFI means "thin film ignition". Somewhere along the way JeepHammers teamrush upgrade got renamed.
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Unread 11-14-2012, 01:19 PM   #5
347jeep
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Quote:
Originally Posted by gosupes View Post
I think he is using the HEI only as an ignition module, the rest are the Ford components. If you have 2 wires going to the positive coil terminal, this is switched power so figure out what else is tapping into that power source but it's probably from the starter relay. For the 2 wires to the neg coil terminal, this is the signal from the ignition module and there should only be a single wire from the neg coil terminal to the ignition module.

Here is a basic write up with some pics, probably from someone on this board as I recognize some of John Strenk's pictures as well as Jeephammer's. Similar to what I run, I didn't worry about the coil connector and used 12awg wire (what I had laying around) and soldered on female spade terminals to connect with the coil. Been reliable for last 6+ years.

http://www.fairpoint.net/~julienjim/...ion%5B1%5D.pdf
Ford tfi coil, GM HEI 4-pin ignition module

The coil negative will have the signal wire from the HEI module as well as tach signal.

It would be nice if I could stack ring terminals like I could with an oil filled coil.

What size is the spade on the coil? 1/4 inch?
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Unread 11-15-2012, 08:11 AM   #6
gosupes
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Quote:
Originally Posted by 86cj74.2L View Post
Are you using the e-core ford coil and a stock duraspark ICM and its lasted 6+ years. If so I'm very impressed.
No, the duracrap module died a long time ago, using a HEI 4 pin module. Keep a spare in the glove box just in case, but as long as you keep a heat sink on them, they should last.

Quote:
Originally Posted by 347jeep
What size is the spade on the coil? 1/4 inch?
Yes, pretty sure. I forgot about the tach signal. My tach wire is tapped in at the HEI terminal. Funny how you forget things when you don't look at them for a while.
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1986 CJ7, 4.2 w/4.0 head, TFI-HEI hybrid ignition, Clifford manifold w/Holley 390 w/cold air intake, OBA, 4.5" lift, Woody CV shaft and Tattons in front, 4.10 gears - lunchbox in front, Truetrac in the back, twin-sticked, blower upgrade for running topless, trying to keep it simple.

It's just a Jeep, and if you don't wheel it once in a while, it's not even that.
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Unread 11-15-2012, 03:45 PM   #7
347jeep
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Quote:
Originally Posted by gosupes View Post
Yes, pretty sure. I forgot about the tach signal. My tach wire is tapped in at the HEI terminal. Funny how you forget things when you don't look at them for a while.
So I was wondering, why exactly is the TFI commonly the coil of choice?

I currently have a HEI hybrid ignition system using the MSD Blaster 3 oil filled coil and it is going out. Needs to be replaced. It lasted about a year. My first thought was to go to the TFI like most others do, but I am now begining to wonder why it is the coil that most use.
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Unread 11-15-2012, 03:58 PM   #8
347jeep
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Another thing, how do you tell which prong on the TFI is positive and which is negative? I had one years ago (oem application) and it wasn't labled and didn't need to be since the plug would only go on one way. If I am using spade connectors then I would need to know.
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Unread 11-15-2012, 03:59 PM   #9
CSP
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The e-core coil (correct term) simply packs more of a punch than the oil canister type coil.

Look inside the plug area at the terminals. They are marked "+" and "-".
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Unread 11-15-2012, 07:52 PM   #10
86cj74.2L
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The e-core style coil has less iron in it then the can type. So it's reaches its saturation point earlier. (Less dwell time........or think of it as how long the coil is shorted to ground)

With less saturation time at higher rpm's where their isn't a hole lot of time between sparks. That has a advantage. MSD gets away with using their can coil because its throwing 400v at the primary side of the coil which makes it saturate faster. I think it's something like .03 micro seconds for the e-core and .06 micro seconds for the can type coil. That's twice as long.
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