| Parts
List : |
GM
HEI Distributor |
|
| Distributor
Rotor |
| Distributor
Cap |
| New
Spark Plugs |
| 8mm
Spark Plug Wire Set |
| AMC
V-8 Drive Gear |
| Tools
Required : |
½”
open end wrench |
|
| Phillips
screwdriver |
| Long
flat head screwdriver |
| Wire
cutters |
| Soldering
gun and solder |
| Volt
meter |
| Spark
plug gapping tool |
| Socket
to remove spark plugs |
| Timing
Light |
| INTRODUCTION:
This
write-up is to provide information to Jeep CJ (and some YJ’s w/
258’s) owners who would like to get more power out of their
258cid inline 6 cylinder engine.
The factory Duraspark ignition systems are troublesome and
exhibit hard starting, poor fuel economy, poor idling, and
hesitation.
The GM HEI (High Energy Ignition) system will resolve all
of the previously mentioned problems by providing a stronger and
fatter spark.
Hopefully I will be able to answer questions about this mod
that other write-ups have not.
This mod is a direct bolt on to CJ’s without ECM’s.
To do this on a CJ with an ECM the “Nutter Bypass”
should be performed so that the ECM doesn’t control the spark,
or the carburetor anymore.
To do this
project you will need the following:
GM HEI distributor, AMC V-8 drives gear, cap and rotor,
sparkplug wires, and sparkplugs.
|
|
| Find
an HEI. I found one a
junkyard for $15. You
can purchase a new one, but a used one will do just as good.
To find an HEI from a junkyard or an auto parts you want
look for a GM vehicle from 1976-82 with a GM 250cid inline 6
cylinder. I found
mine in a 1980 Chevy Van. |
|
| The
drive gear on the HEI will not work because the teeth go in the
opposite direction compared to the gears on AMC engines. You
will need a V-8 drive gear from an AMC V-8 (either a 304 or a
360). I have heard
that an '83 or newer gear is what should be used but all AMC V-8
drive gears are the same so any should work.
The picture shows the AMC V-8 gear on the distributor
(left). The stock GM gear that came on the HEI is on the right.
Notice the teeth and how they are opposite. |
|
| Since
the HEI I used was from a junkyard, I cleaned it with brake cleaner
and made sure the advance worked correctly.
I got a new cap and rotor, just so if there were any
problems those 2 items would be automatically ruled out.
Put the new rotor on the distributor and transfer the coil
from the old HEI cap to the new one (4 bolts).
Be careful when removing the spade connectors that the 3
wires attach to from the base of the distributor. |
|
| After
you have done the first 3 steps you are ready to put the
distributor on the engine.
I looked at the old distributor cap and found which wire
went to piston # 1, and marked it.
I marked it on the heater hose with a sharpie marker.
It’s not a 100% accurate; just a ballpark figure (we’ll
adjust the time later).
After you have a reference where the wire went for piston
#1, remove the factory distributor cap.
Now rotate the engine (clockwise) so that the rotor (of the
factory distributor) is pointing toward the mark /reference point
you made.
Now you are at TDC of piston # 1.
You can also check it against the marks on the timing
cover/harmonic balancer. |
|
| Remove
the old distributor by removing the bolt (should be ½” head)
and U-shaped fastener at the base of the distributor, and unplug
the wires that go to the Duraspark box.
Remove the old coil because the HEI cap would hit it if it
were left on the engine. Install
the HEI distributor so that the rotor is pointing to the mark /
reference point of that of the old distributor.
If the HEI distributor won’t go all the way down, remove
it and see what direction the keyed section of the distributor
shaft is facing and then turn the oil pump w/ a long handled
screwdriver so that the keyed part of the shaft can slide into
place. In the pic the
rotor isn’t facing exactly where the old rotor was pointing but
the base of the HEI can be moved to make up for that. |
|
| Install
the HEI’s cap, spark plugs and the spark plug wires.
The spark plugs should be gapped at .045 to get a nice big
fat spark from the HEI. The rotor should face one of the attachment points on the cap
for a plug wire. If
you put the cap on and notice that the rotor isn’t facing a plug
wire connection, adjust the base of the distributor so that it is.
This plug wire is now #1.
I found from other write-ups that Plug wires from a 1977 to
83 Ford Fairmount with an inline 6 work well.
They automatically come in the 8mm size.
They ran $15.99 from Auto Zone.
The firing order (in a clockwise direction) is 1,5,3,6,2,4.
The engine is numbered from front to back, with the front
most piston being #1 and the rear most piston being #6.
|
|
| Locate
the power supply that goes to the factory coil.
You can trace that wire to the wiring harness where it
exits the firewall on the driver side, or you can locate the
Duraspark box and find the fattest wire coming out from it.
Trace that wire up to the harness and notice that it is
spliced into 3 other wires (one of them being the power for the
coil). Out of those
wires find the one that goes to the harness, where it connects to
the firewall. You
want to use the wire coming off the harness.
Cut away the rest of the wires.
The Duraspark box is now dead.
This wire coming from the firewall has a constant 12V
during startup and while the engine is running.
You want to use this as the power for your HEI.
Why can’t I us the positive wire that supplies the
factory coil with power you ask? Well the factory coil can’t accept a constant 12V during
running of the engine. The
wire that goes to the factory coil has a resistor wire spliced in
and drops the voltage down to somewhere around 9.6 while the
engine is running. This isn’t enough voltage for the HEI, and it won’t work
properly.
|
|
|
Now you are ready
to start the engine. It
should start. If it doesn’t, you can adjust the base of the distributor.
If it is running rough, you can set the timing with a
timing light. A lot
of people with CJ’s and the HEI conversions said that they
usually run 8 degrees BTDC, and it works well for them.
Disclaimer: This
write-up is for information only.
I will not be held responsible for what you do to your
vehicle. If you have questions, email me at kvarady@verizon.net
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