AMC 360 V-8 Easy Ignition Upgrade

Aug. 20, 2008 By Joel Kilby
This image shows the completed ignition upgrade.  Off-the-shelf parts keep the conversion affordable and make sure parts are readily available should they ever need to be replaced.

I got my 1988 Jeep Wagoneer in a well-used condition.  However, she was rust free and ran well enough to drive home.  Whenever I pick up a used rig like this, I like to go through it and get some of the basic maintenance done.  That usually clears up any minor issues that come from neglect and/or high miles.  It also gives me a good baseline for what has been done, and when it needs to be done next.

With this FSJ, I immediately noticed that the old beast seemed to start up slowly and idled just south of rough.  Acceleration was not too bad but it was not as smooth as it should have been.  No doubt 160,000 miles on the clock put the old AMC 360 V-8 in a bad mood. 

After searching around online for some solutions, I started zeroing in on the ignition system.  I wanted an inexpensive upgrade that I could do in a weekend and with parts that I'd be able to get again should the need arise.  I settled on a conversion using some of the parts from Ford's Thick Film Ignition (TFI) system. 

TFI ignition systems were used in numerous Ford vehicles from around 1985 to the mid-1990's, which make parts for the system abundant and inexpensive.  The setup I installed in my Wagoneer has been a popular upgrade in the FSJ crowd for a long time.  It is well-documented and field-tested as being a reliable upgrade. 

For my project I used easily attainable parts from a big, old 1986 model year Ford 460 V-8.  This conversion should work on any AMC 360 from 1975 and up.  Given the notoriety of some Jeep owners swapping unimaginable things into their rigs and the factory's habits of changing parts mid year your results may vary.  However, generally the motors in FSJ's from 1975 on were equipped with Duraspark ignitions which will respond well to this upgrade.

This conversion replaces the following ignition components:
Ignition coil (Wells P/N C839)
Ignition wires (Any set of quality 8mm wires will work)
Distributor cap and rotor (BWD Automotive P/N C194Z)
Spark plugs (Champion RN12YC gapped to .045")

The factory AMC distributor cap is on the left.  It uses outdated well-type terminals that don't give a solid connection.  Since the new coil outputs more voltage it is also helpful that the new distributor cap puts more distance between the terminals.  This keeps the powerful spark from ""crossfiring"" between two terminals at higher RPMs.

Start off just like you would with a normal tune-up.  First, you'll want to gap your plugs.  The new coil will provide more voltage to the plugs, and this enables a wider gap.  I gapped my plugs to .045" with favorable results. 

Swap out your plugs one by one, and install the new wires to mate them up to the corresponding terminal on the new distributor cap.  The first thing to note about the cap in this swap is its larger diameter.  It puts more distance between the terminals the rotor hits so potential crossfire at higher RPM is eliminated.  You'll also notice the newer male terminal ends on top of the cap provide a fool-proof connection for the wires.

Once your wires and plugs are set, clip the adapter to the distributor body and the cap/rotor assembly on top of that.

Remove the can-style ignition coil and replace it with the new TFI coil.  Unlike the original ignition coil, the Ford coil can be mounted in any orientation.  Some people have had success pulling a mounting bracket out of various V8 motors in junkyard trucks and Mustangs.  I opted to purchase a bracket custom made for the AMC 360 from Baybilly on IFSJA.org.  His bracket included a steel spacer to clear my Jeep's York air conditioner compressor.  It secures the TFI coil by 4 bolts on the corners, and mounts to the AC bracket by way of the rearmost bolt.  It tucks the TFI coil right up next to the air cleaner when it's all said and done.  If you'd like to use that bracket, contact Baybilly (Dave Spaulding) at dentonraid@aol.com .

I connected the ignition wire from the coil's terminal to the center point on the distributor cap to polish off the install.

Here you can see the new coil mounted using Baybilly's bracket.  It tucks up next to the air cleaner behind the A/C compressor.  At the bottom of the bracket you can see a hint of the spacer that helps the unit clear the A/C mount.

I immediately noticed a difference in performance when I started the Jeep.  It fired up in less than half its usual cranking time, and the old FSJ's idle seemed to smooth out a bit, too.  Driving down the highway a seat-of-the-pants test revealed smoother acceleration all the way up to cruising speed.  

But after putting a few thousand miles on this setup I have some suggestions.  None of these are "required" but they may save you some headache.

To really get full gains from the upgrade, you should think about installing a more reliable ignition module. This is the gray box on the driver side fender well.  It's notorious for getting hot under the hood and breaking on a somewhat regular basis. About three months after I installed the TFI system, my ignition module failed and left me stuck in a parking lot while I tracked down a replacement.  MSD makes a reliable alternative to the stock module which can be wired in.  When time and the checkbook permit, I'll be adding that to my system.

I was also having issues with the wire from the distributor to the coil coming loose.  I found an Accel single replacement wire (P/N 170500) that included several different terminals and boots.  Now it snaps into place and won't vibrate loose.

Swapping out tired old stock parts in favor of off-the-shelf TFI pieces is not a big job but it offers bang-for-the-buck that rivals any other upgrade.

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