I have had several people email me for directions on the wiring of a
four
pin GM HEI module and a 280 dist, so here it is.
Many of us have heard the down side of these modules as being
limited
to 5000 rpm on an 8 cylinder eng. Actually these modules are
not limited
by the operating frequency but rather the original coils were the limiting
factor. The original coils where mounted in the top of the distributor
cap,
where the temperature is quite high. Also as the frequency increases
the amount of time for the primary winding to cool decreases, so the
effect
is as the temp of the coil rises so does the resistance in the coil,
which
decreases the output. This is why MSD claims that if you replace
the coil
in the cap with there Blaster coil it will increase the max rpm to
6000.
This setup with a MSD blaster coil can work to 7500 rpm on a six cylinder
engine.
---------------
/
\
/
\
W\ ------------- /C
G\/
\/B
W= positive lead from the
pickup C= negative side of the coil
G= negative lead from the
pickup B= positive side of the coil
First, mount the mod to a piece of aluminum .060in - .125in thick.
Make
sure that you use the silicone grease that comes with the mod.
I typically
mount the mod to the bottom coil bracket bolt. The following
wiring
directions are for 240 z models. There are two black with white
tracer
wires. For convenience, I connect the short one to the + side
of the coil.
Now connect the longer black and white wire with the green and white
wire
to the mods terminal B. Then a wire is connected from the coils
negative
terminal to modules C terminal.
Here are some tips for swapping the distributors. Before you remove
the
old dist turn the engine to 10 degrees before TDC, make sure it is
on the
compression stroke by observing the direction of the rotor, it should
be
pointing at the number one spark plug lead. When installing the
new dist,
turn the dist body so that the #1 spark plug lead is lined up with
the rotor.
In both cases you may want to mark the distributor bodies with the
location of the number one spark lead, so that you don't have to keep
installing the cap to check for its location. If this is done
the timing
should be set at approximately at 10 degrees BTDC, which should allow
the
engine to be started so a timing light can be used.
----------------------------------------------------------------------------
----
Andy Levy (allevy@oboe.aix.calpoly.edu)
California Polytechnic State
University, San Luis Obispo
----------------------------------------------------------------------------
----
Date: Sun, 12 Mar 1995 19:49:02 -0800 (PST)
From: Andrew Levy <allevy@violin.aix.calpoly.edu>
To: Z-car <z-car@CS.Princeton.EDU>
Subject: ignition - HEI
Mime-Version: 1.0
Sender: snd@CS.Princeton.EDU
Precedence: bulk
Here are the details on the
HEI ignition system that I'm running.
Sorry about the delay with this info. I have been too busy filling
sand
bags trying to save my property from the severe flooding here in central
CA.
About three years
ago I built a L28 for a friends 70.
I intially set it up with a MSD 6A and a 76 dist. After a month
or so
the MSD failed. So in order to get the Z on the road again I
went down to
the local autoparts store and got an HEI module, it cost about $25
dollars.
Went back to the hooked it up and realized that it worked every bit
as good
as the MSD. I have used HEI mods. in many applications before,
but never
compared them to other electronic ignitions.
Here are some benefits to
this system. First, the stock
tachometer will work with out any extra devices. Second, they
are sold
everywhere and only cost $20 - $30 dollars. Third, they seem
to be more
reliable than the aftermarket ignitions.
The installation is quite
easy and should cost less then
$100 dollars complete. The parts needed are a magnetic pickup
\ reluctor
type of distributor, and a four pin HEI module (Standard ignition pn
#
LX-101) or equivalent, no ballest resistor is needed.
First you need to determin
the polarity of the wires going to the
distributors pickup. Some have a red and a green wire, the red
is the
positive. If you have one with two green wires or you can't tell what
color they are you will need to test them. This can be done by
rotating
the dist. shaft the same direction as it would be turned by the engine
and
use a volt meter to establish the polarity. This system generaters
AC
current so look for a positive reading when the raised portion is
approaching the pick up and negative when it departs. You could
try to
establish the polarity by starting the engine and use a timinglight
to
check each combination, the one that gives you the most retarded timing
should be correct.
Below is a drawing of a
average HEI module, the letters refer
to the pins. I mounted the HEI mod. on a piece of aluminum ,
sheet .o6o"
thick which bolts to the fender via. the bottom coil bracket bolt.
Remove the factory ballest res. and locate the two black-white wires,
short
and long and the green-white wire. The longer black-white wire
will
connect to the positive side of the coil. The short black-white
wire will
be connected to the green-white wire. A piece of 14-16 gauge
wire will
need to be run from the positive side of the coil to pin B on the module.
Another piece of wire will need to be run from the coils negative to
pin
C on the module. The positive wire from the distributors
pickup connects to
pin W and the neg. from the dists. pu. connects to pin G. I connected
a
ground wire from a dist. hold down bolt to the HEI bracket. Make
sure
you use the silicone sealer that comes with the module between the
bracket and the mod. If the the module is not grounded well it
will fail.
/-------------------\
HEI module ->
/
\
/ W
C \
/\ G / - - - - - - \ B /\
dist. + /\/
\ /\ - batt.
-
+
This setup will not work
with all coils. It works best with a MSD
blaster coil. You can mail order these coils from Summit and
Jegs for
about $25. I have gotten distributors from wrecking yards for
$25-$40
dollars. The distributors where used in datsun 810's and Zs.
These dist.
are very reliable electrically, but not so mechanically. There
is a
plastic cage that holds three, 3mm ball bearings half of the time it
is
broken or the balls have pitted the the thin spring steel races. This
only
effects the operation of the vaccum advance. I don't run vac.
adv. with
S.U. carbs. So in this case you could solve this problem with
epoxy.
Another solution is to replace the bearing and cage with bushings made
of
brass bronze or teflon PTFE. I have also modified these dist.
to use
torrington bearings.