What started as a bit of play in the distributor
shaft of my '79 ZX has become me making and selling distributor
bushings. The details about the bushings and purchasing
them are on another page and I would suggest reading through the rebuild
very carefully before purchasing them. I will concentrate on rebuilding
what I feel was the best of the distributors, the D4K8 and D6K8 series
for the 280ZX models 79-83 (more information on these is available at Jason's
page). Why are these the best? Because, they have a solid state ignition
module that is attached directly to the distributor housing making it extremely
easy to put into earlier model Z's. I actually
rebuilt one of these to go into my 70 240Z and replace the point unit distributor.
It is an easy exchange and one which will be discussed
in this page. While the ignition module changed during the course of
evolution, the distributor body remained the same and I have rebuilt distributors
from 83's and simply put an earlier model ignition unit on them. A very
good discusion about the merits of the different distributors is Jason's
Regardless, I assume you found this page because you feel
that your distributor needs some work.
A nice thing about the Z's is that
the distributor drive shaft is asymmetric. You can simply remove the distributor
and not have to worry about putting it back in and lining up a gear. However,
if you want to practice good automotive repair habits: turn the crankshaft
to TDC and see if the rotor is lined up with the #1 sparkplug wire on the
cap (remove the cap and see if that is where it is). If not, turn the crankshaft
one more time to TDC (it turns twice for one rotation of the distributor)
and now it should be lined up. You should already have the cap off, so
go ahead and remove the vacuum advance hose and the ignition module connector.
Remove the two 10 mm bolts at the base of the adapter where it connects
to the timing chain cover. There you go, that was easy.
I often get emails about the ignition
module failing (on the side of the Dizzy).
This failure is usually very easy to diagnose. You could be driving along
just fine and then the car quits - Tach drops immediately to zero. It usually
occurs after the car has warmed up or gotten hot. After you let the car
cool for a few minutes it starts up again without a problem as if nothing
happened, then it does it again...Because a number of Z heads feel that
the ignition modules are outrageously expensive, they have developed a
way to use a
much cheaper GM ignition module with earlier model distributors. Not
of interest to me but maybe to you.
Before discussing the rebuild, it is
worth deciding if your distributor needs rebuilding! Even if you just replace
an ignition module, it is worth making sure the rest of the distributor
is working properly. Usually distributor problems come on gradually and
are characterized by poor idle, or poor gas mileage. Sometimes you can
put a timing light on each spark plug wire and see a miss occasionally.
Poor gas mileage can also be attributed to a failing vacuum advance system.
This can fail in two ways. First, the vacuum dashpot may have a hole in
it. This is easy enough to check, just get a piece of hose, attach it and
try to suck air through it. Second, the breaker plate which the vacuum
dashpot turns falls apart and the ball bearings it rides on fall out of
place. It gets stuck, and no more advance.
You can actually check the distributor
shaft for play before removing it, but I like to check it out of the vehicle.
First, the shaft should turn freely. You might feel the reluctor points
as they pass the stator points (see image), but they
should not touch the stator points. Further, they should all have about
the same clearance. You might find that contact has already broken or worn
a couple of the stator points. Wiggle the distributor shaft and see if
you can get the reluctor and the stator to make contact. If so, the bushings
are shot. Some people have also reported the bushings "screaming" or clearly
making noise. This might be solved by simply rebuilding the distributor
and greasing the existing bushings.
Returning to the exterior of the distributor:
Remove the cap and rotor - straight forward.
Remove ignition unit - it should already be marked with red/green.
Use needle nose pliers to remove connectors.
Remove the 3 bolts holding the stator in place If
the reluctor does not come off easily, then remove this before trying to
pry off the reluctor! If you do not, you may
damage it! It should come off easily, but sometimes the pickup coil sticks
to it. Don't break the magnet!
Here is a picture
of the stator (not a good one unfortunately). It has a magnet behind
it - if the magnet is cracked or broken, then, in my opinion, it needs
Now, with the stator out of the way,
you can pry the reluctor off. Without the stator out of the way, prying
the reluctor off always results in a broken stator
Remove pickup coil, and check that
it has ~ Ohms resistance.
Remove screw from vacuum advance to
breaker plate. Then remove vacuum advance dashpot.
Remove the two screws holding in the
breaker plate. Don't worry about direction, you can check it from the image.
Remove breaker plate. Note if the ball bearing cage on the
breaker plate has broken and the ball bearings have come loose. The breaker
plate should rotate freely back and forth.
The shaft is now free to be removed, but
check it for play and rotation now that the junk is off. You might have
to clean the end of the shaft that the collar
was on with a 3M scotch pad (not steel wool,
it is a green nonmetallic dish pad) before it will slide out of the distributor
housing. There is one washer between the housing and the collar and three
thin washers between the shaft assembly and the inner flanged bearing (see
image). Sometimes the flange breaks and it appears that you have four
washers in the distributor - one which is rather thick...
Remove bottom adapter: first note or mark with a scribe the
position on the adjustment plate.
Remove adjustment plate: scribe top on the top. This is necessary
if you are going to bead blast and paint it. I put
dents in the top.
Remove the collar by pushing out the roll (spring) pin. This
is a cheap item, just plan on replacing it.
If you decide to remove the governor
weights etc., be warned that upon reassembly, you can get the rotor and
the shaft 180 degrees out of alignment. When reassembled, the short side
of the alignment slot in the bottom is on the same side as the rotor contact
(see picture - ok, it isn't a great picture, but
it could save you some trouble).
Clean up the shaft with the 3M
scotch pad and some soap and water (or solvent if you like) and visually
inspect it for damage. Make sure you clean out the oil groves at the bottom.
Here is an image of a nice clean distributor shaft.
Even the oil grooves at the bottom have been cleaned. If the top of the
shaft were the reluctor attaches was rusted, clean this up with sand paper
or a file, then oil it. This is when you decide to replace the bushings
or not. Clean it, and then grease it with a little molybdenum grease and
return it to the housing. How much play is there? Does it freely rotate?
I just pulled a distributor off of an '83 280ZX that had 110,000 miles
on it and the distributor bushings were fine. A little wear is normal,
but deep grooves could prevent the bushings from working effectively.
Ok, now if you decide that the bushings need to be replaced,
I strongly advise getting a distributor
from the junkyard and rebuilding that one!
Or having a back up plan in-case the
bushings will not press in or there are un-forseen difficulties because
removing the old bushings will destroy them - there is no going back! So
far only about 1/3rd of the bushing replacement attempts I have made have
been succesful! Now that you have a distributor from the junkyard, check
it as above, and see if it needs to be re-built. No surprise if it does.
It has probably seen more or equal mileage as yours. Go ahead and clean
it up and see if it needs to have the bushings replaced. Of the two distributors
that you now have, replace the bushings of the one which is in the worst
condition. Mix and match shafts if necessary to get a nice, woblle free
distributor. Try the replacement bushings on the shaft. There may be a
little bit of play, but once they are pressed in, this will disappear.
Time to remove the old bushings. I use a nut driver and
a hammer (click on image for larger image).
This step, however, will
destroy the old bushings, so make sure that you do need to replace
them! Knock the bottom one out, flip the unit over and knock out the flanged
one. Before going further, see if the new bushings fit. Actually, they
shouldn't. They should be just barely too large to fit. If they slide in
easily then there is a problem and you should contact
me. After checking the bushings, I solvent clean the whole distributor,
then seal up the interior with rags and masking tape, cover machined areas
with tape, and bead blast it. Aluminum will oxidize so it is necessary
to seal it after bead blasting. I use a product called Steel Wheels (one
of my favorite
products) which holds up well and I like the color (see
After you have cleaned up the distributor
it is time to install the new bushings. Using the back of a hammer, gently
tap the bushing in. For the bottom bushing, it may be necessary to put
the distributor on a block to prevent bending the cap hold downs (image
below click for full size image).
Now that the bushings are in place, put some molybdenum
grease on the clean distributor shaft, and the 3 washers that go between
the flanged bushing and the shaft (see image), and
slide it into the housing. It will be a little difficult, but once it is
in all the way and the bushings lined up with where the old bushings were,
it should turn very smoothly! Check it at this point, it should turn smoothly
and have no side to side play....
Now it is time to start putting it together.
Through-out the rebuild process make sure
that the shaft turns freely and doesn't rub. For some reason one of the
problems I encounter is that the replacment bushings "cock" the shaft at
a slight angle. Why this occurs I do not understand but may be do to the
manufacturing process with the original bushings...
Clean and regrease the ball bearings on the breaker slide
if you didn't replace it.
Return the breaker plate with the cap
locator in the right position as well as the hole for the vacuum advance
Install vacuum advance dashpot, and test that a vacuum rotates
the breaker plate.
Check to make sure the shaft turns easily: if not find out
where it is hanging up.
And there you have it! I would suggest either replacing the
wires and plugs before doing this (making sure the car runs after your
work) or after this, but not at the same time. If you just work on one
item at a time if the car doesn't work, you only have to trouble shoot
one item....Hopefully your car will run much more smoothly after this operation.
Install pick-up coil and then stator, but don't tighten down
yet (again check that it is rotating freely).
The reluctor may need to be tapped on (use an oversized socket)
the shoulder in the up position. Make sure
the roll pin is in place.
Now rotate the shaft and see if there is contact between
the reluctor and stator. You haven't tightened down the stator yet because
you want to align it so that the gaps all the way around, while rotating
remain the same. Tighten the stator down firmly, but don't over tighten,
you may break the magnet.
Attach the ignition unit and wires.
Now, I usually add the collar last so that I can check for
rotation throughout the whole re-assembly. At this point grease the bottom
of the distributor, add the washer and the collar. Tap the roll pin into
Put the adapter plate and foot back
on adjusting so that it is in the same orientation as before. You should
have labeled the positions to make this easier...
Return it to the auto.
into an earlier Z:
I hate adjusting points! When I found
out that I could put an electronic ignition in my 1970 240Z I jumped at
the opportunity! When I found out that it was only a two wire swap, I was
First, turn the crankshaft to TDC and
see if the rotor is lined up with the #1 sparkplug wire on the cap (remove
the cap and see if that is where it is). If not, turn the crankshaft one
more time to TDC (it turns twice for one rotation of the distributor) and
now it should be lined up. Then, disconnect the ground terminal at the
battery, the wire running to the distributor and, finally, remove the original
distributor (special note, remove the distributor with its respective adapter
plate, that is, remove the complete distributor from the timing chain cover).
Now, put your D4K8 distributor in palce and wire her up! Here are schematics
(much thanks to Dick Denno):
Original Wiring (click image to view)
Modified Wiring (click image to view)
Note: these are currently lousy pictures - I will improve
them in the future!
If you can read schematics, then there
you have it! If not, then what you need to do is take the wire that was
originally going to your points (from the minus pole of the coil) and connect
it to the C connection on the outside of the ignition module. Then run
a second wire from the B terminal on the ignition module to the plus connection
of the coil. The connection to the balast resistor from the coil should
allready be there. Now, just short out the balast resistor. I left mine
in place and simply ran a wire between the two connectors.