Why I started this project - Vintage Lamborghini Garage



Espada Single Distributor

Cap/Rotor/Points

Conversion

Bob Staaterman 9/15/2008

I was faced with getting a new cap, rotor, points and ignition wires for my series II car.

The cap & rotor alone are quite expensive so I looked at the various alternatives. I found out that for my car the Jag cap utilized by some others would not work on the style of rotor I had. So I looked into adapting the Jag cap & rotor to work on my distributor. It turns out that I only needed to make a mounting adapter for the Jag rotor and then everything would work.

I also wanted to eliminate the points but I preferred to have the car remain stock looking so I went with the Pertronix Ignitor system which is completely self contained in the distributor body even with dual sensors that were replacing 4 sets of points. There’s more room now than before. Pertronix also has an Ignitor II series which has additional features but Pertronix claims that two of this type of sensor will not fit in that distributor housing. I’m not so sure about that. The Ignitor II series also will not work with solid core wires.

I did think about the various crank triggered digital ignition systems that some have successfully installed but since I wanted an original look these were not appropriate. It’s very clear that technically, the direct digital ignition systems are a superior solution. There also are other points replacement type systems available, which have been quite successfully installed in these cars but these all required two external boxes. Some actually still utilize the points as a low current switch. That I did not want.

To begin with, I sent the dizzy off for an initial test on a Sun machine to determine what was happening and whether it required a lot of rebuilding. I was lucky and except for the points which were a disaster the bearings and advance mechanism were very good. If I had to spend a lot of money fixing the advance mechanism I might have opted for the digital direct ignition solution.

Servicing the dizzy.

I’m not going to go into the details about a complete servicing of one of these distributors because that’s not within the scope of this article. There are much more qualified sources of information available for that topic. Briefly then, if you look at figure 1 you can see the depression mark worn in the cylinder by that spring-loaded pin in figure 2. The bright mark on the tip of the spring-loaded pin in figure 2 is the wear mark. What was recommended to me was to use emery cloth to smooth out the depression area in the cylinder (figure 1) and make the tips of spring loaded pins in the weights uniform in shape. These pieces were reviewed by someone who does a lot of rebuilding and calibration of the Ferrari versions of these distributors and he suggested this approach as the wear was not that bad. If yours is worse then you had better get some expert distributor rebuilding advice. This part of the distributor was then cleaned lubricated and reassembled. These types of greases were recommended to me.

Go to and enter the part numbers from below.

Dupont Krytox Synthetic Grease and Oil High Temperature Xht-AC Grease, 2-Ounce Tube # 10195K25

Dupont Krytox Synthetic Grease and Oil Extreme Pressure Gpl 215 Grease, 2-Ounce Tube # 10195K32

Figure 1 Area of Depression Caused by Centrifugal Weight Contact

Figure 2 Centrifugal Weight with Spring-Loaded Pin

Parts List For The Conversion

I used a Jag V12 Marelli cap & rotor from the later XJS model. There are knock-offs out there, which I’ve, been warned to avoid. I got mine from a Jaguar dealer for a total of about $220. The price is reasonable; it’s authentic Marelli and years from now these should be a lot more available than the Lamborghini based ones.

I used an aluminum bar for the rotor adapter. I had the holes precision milled for $25. McMaster #6023K191 About $12 and you only need 2” of the 12” length. So, you can do 6 cars!

A big brass washer serves as the adjustable mounting base for one of the sensors. McMaster 92916A231. About $5. The washer had to have the center hold enlarged a bit to fit.

Pertronix MR-161 kit supplies the V6 reluctor and one sensor.

Pertronix 1847VC kit for a VW bug supplies the other sensor. You can throw away the rest of the kit.

Both are available from Summit Racing and other sources.

Aluminum tape as used for ductwork or Lucas backing for anti-vibration on brake pads (what I used). This tape makes the reluctor fit tightly onto the cam of the dizzy. It serves as an interference fit shim. The adhesive backing only serves to help in assembly.

I used Loctite, the wicking variety for placement on the screws and nuts after final alignment.

You can use a 9 volt battery for testing.

De Plane Boss, De Plane

Let’s begin with a brief discussion about the dual plane operation of this distributor before we modify it. This is a dual plane distributor whose properties can be observed by looking at figures 9 through 16 where the cap & rotor conversion pieces are illustrated. It may be helpful to reference these figures as you read about the conversion process. Looking at figure 6 you see plug wire position #1 is show and then 60 degrees later #5 is shown on the distributor body. These two positions operate on the lower plane of the distributor and fire via the same sensor and lower rotor arm. In between #1 and #5 is another plug wire position that operates on the upper plane.

The firing sequence of this engine is 1-12-5-8-3-10-6-7-2-11-4-9 and it alternates between each plane after each firing of the ignition. So the lower plane wires are sequenced skipping one position (the upper plane ones) in between each one as follows 1-5-3-6-2-4. That’s why # 1 and # 5 are marked for testing purposes on the distributor body.

In a similar manner the upper plane wires, which are serviced by the upper arm of the rotor, are sequenced starting at the cap position that’s 180 degrees opposite the #1 position plus a counter clockwise rotation of 30 degrees. More simply put, after #1 aligns and fires the next rotor arm to align with a post is 30 degrees counter clockwise on the opposite side of the cap and on the upper plane. So those wires are assigned skipping a post (lower plane ones) in between each one as follows 12-8-10-7-11-9.

Play with the distributor for a while and observe all of these relationships.

Sensor Installation.

I laid the sensors out myself 150 degrees apart (multiples of 30 will work) with the ability to adjust the sensors. I did the drilling and tapping required with ordinary shop tools. There are no permanent changes to the dizzy so this is a completely reversible modification.

Figure 3

There is an aluminum base plate supplied with the kit MR-161 that you see in figure 3 underneath the large brass washer. It is secured with two of the original flat-headed slot style screws. Note that the holes are slotted. This allows alignment of the bottom sensor (which is fixed in place to the aluminum base plate) relative to the distributor body. The top sensor is fixed in place on the brass washer with adjustment provided via slots in the brass washer. Those slots can be seen around the bottom sensors post mounts.

To adjust the bottom sensor you loosen the two original flat-headed slot style screws and rotate the aluminum base plate. This moves both sensors at once. I utilized the bottom sensor for my lower plane

portion of the distributor. That includes the #1 plug wire position.

To adjust the top sensor you loosen the two nuts on the bottom sensor and rotate the brass washer then re-tighten the two nuts.

To accomplish these adjustments I printed a degree wheel, laminated it to poster board, cut out the center and made an alignment index notch so that I could slip this over the distributor body. This is shown in figure 4.

Figures 5 through 8 show the various alignment marks I made on the distributor one of which, the #1 plug wire position, is already marked on the body with a notch as shown in figures 4 & 5. I would suggest that you study the distributor for a while and become familiar with how things are aligned with the dual plane nature of this unit. I ended up putting tape around the outside of the distributor and cap in ring fashion so that I could make alignment marks for this modification and eventually document the plug wire sequence. This makes later installation much easier.

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Alignment Of The Sensors

As the magnetic lobes embedded in the reluctor rotate they cause the sensor to break the circuit which in turn causes the coil to generate the high voltage pulse which fires the plug. To test your alignment you use the 9 volt battery and hookup a circuit with a VOM as described in the Pertronix instructions.

The idea is to adjust that bottom sensor in figure 3 so that the circuit opens just as the rotor is properly engaging the # 1 post on the cap. The blades on the rotor are very wide and can easily accommodate the alignment shift caused by the advance mechanism. I aligned it to be at the 2/3rd mark when at full advance so it ranges in between the first 1/3rd and the last 1/3rd mark on the rotor blade during the entire advance range. I believe that given the wide nature of the rotor blade you probably have a lot of leeway with this adjustment.

Similarly, adjust the top sensor by loosening the two nuts of the lower sensor mounting post. Then rotate the brass washer to align the next distributor post in physical firing sequence on the other plane of the distributor to be just opening the circuit sensor in the same sort of physical range on that post as you did for #1. Eventually the #12 plug wire will connect to this post because it’s the second cylinder in the firing order.

The final accurate alignment between the two sensors at an EXACT multiple of 30 degrees is performed on the Sun distributor machine. You’re just getting the alignment between the two sensors close here. A cap & rotor are not required for the alignment/test on the Sun machine.

You test using a 9-volt battery.

All of these adjustment screws and nuts should be Loctited upon final assembly.

Cap & Rotor Conversion

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

The Rotor Conversion

Figures 12 through 16 illustrate the old saucer shaped Marelli rotor versus the new Jag rotor with the adapter piece constructed from a piece of anodized aluminum bar. Both rotors have an orientation such that the rotor arms are not in alignment with the center securing bolt. So if the new rotor & adapter looked a bit crooked that’s intentional as it matches the original rotor’s orientation.

The screw going through the adapter threads into the center shaft and exits on the other side of the adapter. This is the original screw supplied with the distributor. That screw plus the ones retaining the rotor on top of the adapter should be Loctited.

You will have to measure and determine the location for the cross hole in the adapter that the locking bolt passes through so as to allow for proper alignment of the rotor height when the cap is on. In my case it was positioned closer towards the top of the aluminum adapter bar. . This can easily be measured with a set of calipers and a little bit of patience. After measuring this dimension I had a machine shop do this work for about $25.

The top of the distributor shaft sticks above the adapter bar when it is secured in the proper position. The rotor slips over that protrusion, uses it to centrally locate the rotor and is then held in place with the two screws.

Once again, as you can see from the pictures the rotor arms are not oriented at a 90-degree angle to the adapter nor are they in alignment with that big center bolt. This is so as to duplicate the orientation of the original rotor. I got it approximately correct.

In figure 15 you can see the red dot I placed on the adapter bar. That aligns with the red dot on the distributor shaft and thus ensures you are in phase with the proper rotor blade on the correct side.

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