Most Jeeps with
V8 engines have one of two distributor systems. A Ford
Duraspark system or a Motorcraft points system.
The points
system is relatively reliable and very simple. It
requires periodic adjustment and maintenance using special
tools. The Ford Duraspark system is all electronic.
The distributor contains a magnetic trigger that sends
signal to the controller and spark is distributed to the
spark plugs from the coil. The Ford system is fairly
reliable but failure is usually instant with no warning and
no recovery except with replacement of the controller
module. I was always a good idea to take a new
replacement module along on the trail because these things
always fail at the wrong time.
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The GM HEI
system was used in GM vehicles for approximately 20 years.
It is a simple design using a magnetic trigger, electronic
controller inside the cap, and a coil. A nice feature
of the HEI is the coil is integrated right into the
distributor cap, meaning no coil wire. This feature
allows for a much hotter spark and increased gap on the
spark plugs. There are many aftermarket
high-performance coils available too.
There is a
company called DUI that makes an HEI distributor for Jeeps,
in this particular article we are using a custom made
distributor we bought off eBay. It came complete with
a new cap and coil. The old plug wires will not work
with an HEI. You should buy a custom set of wires, we
used a set of Live Wires from performancedistributors.com.
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HEI Distributor for AMC |
Live Wires HEI wires |
Installation is pretty straight forward.
Disconnect the battery. Remove all the old
Duraspark components (if equipped) Remove
the plug wires making note of the firing order.
Remove the distributor cap. Mark the old
distributor's rotor position so the new
distributor can be installed in the same place.
If you forget this step the engine will most
likely not start or run real bad.
A down and
dirty way to locate the start of a firing cycle is to
remove the spark plug from the #1 cylinder and crank the
engine in short bursts. Put your finger over the
plug hole and feel for the compression stroke to force
air out of the plug hole. Look down at the timing
cover marking and line up the line on the harmonic
balancer to the 0 line on the cover. BE CAREFUL -
Watch out for the fan and make sure the Jeep is in
neutral!
Remove the bolt
and bracket that holds the distributor in and pull it out.
Install the new
gasket onto the shaft and insert the distributor so that the
rotor end is pointing in a direction to allow movement of
the distributor to set proper timing. You may need to
crank the engine 2 full turns to allow the distributor gear
to engage the oil pump drive shaft located below the bottom
of the distributor.
Once the
distributor is fully seated lightly tighten the securing
bracket so that you can properly set ignition timing after
the engine is running.
Wiring up the
HEI is easy. All that is required is 2 wires.
One from a switched 12V circuit and the other from the Start
side of the starter coil. This 2nd wire provides power
to the distributor during engine cranking.
Install the cap
and wires. Starting from the #1 cylinder and moving
clockwise through the firing order.
AMC
V8 Firing Order
1-8-4-3-6-5-7-2
The spark plug
gap can be increased due to the hotter spark provided by the
new distributor. Recommended gap is .050 - .055.
This may be a good opportunity for some new spark plugs.
After all of the
wires are installed check all connections and make sure
everything is cleaned up and out of the way of moving parts.
Attach a timing light so you can set the engine timing after
it starts. Reconnect the battery and start the engine.
If you timed the engine correctly it should fire right up.
You will probably need to rotate the distributor to better
set the timing before you use the light. When the
engine runs smooth you should fine set the timing using the
light. The recommended ignition timing is 8 degrees
BTC with distributor vacuum advance disconnected and the
engine at idle. The Jeep was set a bit higher about 10
degrees, high enough just before engine ping was heard.
If the engine
doesn't start or run correctly you may have the distributor
of time. It is possible that the distributor will need
to be removed and re-timed, refer to the above.
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