DIY Electronic Ignition: Pre-Crossflow and Crossflow

For LUCAS and Motorcraft Distributors

Kris Bubendorfer (c) 2002, 2004

In any case, the original distributor in your Classic Ford is at least 25 years old - and it was hardly a precision piece of engineering in the first place. The upshot is, that the cam that acts on the points will no longer have the original profile due to wear, the bushes supporting the distributor shaft will be tired, the springs that control the advance of the bob weights will have stretched, and perhaps most significantly, the petrol, oil, driving conditions and state of the engine tune are different from those anticipated by the Ford designers - who certainly never expected to see the cars still on the road decades later.

A distributor is responsible for triggering a high voltage discharge from the coil, and directing that spark to the correct spark plug at exactly the right moment to combust the fuel air mixture being compressed within one of the cylinders. In this sense all distributors are equivalent, the only differences being in direction of rotation, advance (both total and curve), and physical fit in the engine.

A few months ago, we bought an MGBGT and through the one of people I met at the annual meet, I heard that certain distributors fitted to certain Japanese cars could be adapted to fit in my MGB. A search on the Internet revealed that the distributor of choice is the Hitachi D4R8X-XX distributor, as fitted to various Hondas and Nissans. The important points being similar shaft size, direction of rotation (counter clockwise) and similar overall shape to the Lucas 25D4 fitted to the MGB. All we need is a little clever adaptation.

Some of you will have already latched onto the fact the assorted old Fords, particularly Classic/Capri, Cortinas, and Mark 1 Escorts are also fitted with the Lucas 25D4/DM2P4 distributor. Score! The other thing is, that the Motorcraft 12100 distributors fitted to the MKII Escorts are also interchangeable.

First steps - what have you got at the moment?

Before I get into any details of what to look for in terms of an electronic distributor, and what to do, the first thing you need to do is find out and record (for later) exactly what your car has as its current fitment. The following table contains a summary of the static timing* information from the UK/NZ and the Australian MK2 Factory Manuals. The static advance was changed to 6 degrees BTDC for all the NZ models, except for the 1.6HC (2V) which remained at 10 BTDC. The Haynes manual lists the 1.3 HC(2V) at 6 BTDC - I prefer to believe Ford.

Right, now start the car, and warm her up. Remove the vacuum pipe from the distributor and plug it. First thing is to check that the mechanical advance is not cutting in early. Connect up the strobe light and reduced the idle until you are sure there is no change in advance. Usually there is no mechanical advance below 1100 rpm, but old weak springs could have altered this. This is the reading you want to record, and is quite likely to be different from the number of degrees you set statically - that's normal, most manufacturers give separate figures for static and dynamic (strobe) timing. I can't find anything but static figures for our cars, and that's why I want you to measure yours. If you don't have a snazzy strobe light that will let you measure the advance by twiddling a dial, just make up a piece of card to read the measurement (use a protractor or extrapolate from the timing case marks).

The other thing to do is record the total advance built in to your distributor. To do this you need to pull it out, and remove the contact breaker plate and look for a number stamped onto the base of the rotor shaft - see next photo. You don't need to do it now, but do make sure you do it sometime.

This establishes your total mechanical advance. It should be 12.5 degrees on the 1600 2V, the graph at the end of the article has the values for the rest of the engines in the range. There are a couple of points to make here. Essentially, this value is in terms of distributor advance, since the distributor turns at half the speed of the crank, this translates into 25 crankshaft degrees. Therefore, the total mechanical advance given by the distributor is static+distributor, and in this case is 10 + 2 * (12.5) = 35 crankshaft degrees total advance

While you are here, check that you actually have the correct distributor fitted in the first place. See above table on static advance. If you are dealing with a MK1 or Cortina, The Lucas distributor has a service number followed by a date code, for example the service codes is 40927A for the 1500, the date code is week+year, so 865 is the 8th week of 1965.

If you have a Motorcraft distributor (and hence a Xflow), then it's the same deal, remove and unscrew the contact breaker plate. You'll find there are two arms with different numbers stamped on each. This photo is not of a 12100 distributor - but the layout is similar.

The advance is the number stamped on the arm that locates with the nylon stop. This is quite cunning, as you can remove the cam and turn it around to select a different amount of mechanical advance. A couple of my distributors are 12.5/12.5 (1.6 Sport 751F 12100AA) and 13/16 (1300L 77BB 12100AMB).

The trip to the wreckers

This will probably be the only time you'll be happy to seen in a Japanese wreckers. What you are after is the Hitachi distributor from a Nissan Sentra/Sunny 1982-1989, or a mid 80s Honda City or Accord. There are of course some caveats, only some models of Honda City are useable, and the suitable model of Accord (JJ engine I am told) is rare - I have not seen one yet. The point is, that whichever you choose, there are pros and cons between these various models, which I will summarise later in this tech guide. Whatever you get, the bearings will be fine, as the absence of side loading from the points, ensures they will last indefinitely.

All of these are two wire (one two each side of the coil) and don't need an external module - so look right in our engine bays.

For now I will talk about the distributors I harvested from my local PickaPart. I came home with four distributors, coils, leads and some spares for under $140, that's a bargain in anyone's book - considering the cost of a Luminition conversion kit.

General Scavenging

You will also want to get some spare vacuum advance canisters. About half of those fitted to the distributors I got leaked. You should check all of the distributors by sucking on the rubber pipe from the carb (yes yuck), and make sure that the canister moves the base plate and holds it. One thing I found useful was looking at older models (points) and taking the working canisters from those. Some people might point out that various canisters have various rates of advance etc. This is true, however, in reality it just doesn't matter.

Nissan

Be careful looking at earlier distributors, such as those in early 80s Pulsars, as these are points based - even though they have the same body and look the same. Check by removing the distributor cap, or by checking the number of wires going to the coil.

The important numbers on the side of the distributor are:

D4R83-30 (1300 cc) and D4R83-36 (1600cc)

These distributors have caps with two screws and a very nice weatherproof gasket.

Both distributors have 14 degree advance (28 crankshaft). These are nice for a number of reasons, they have an o-ring, they are almost the right body length and require little modification.

Honda

The nice thing about these distributors is that they have a distributor cap held on with normal clips rather than screws as with the Nissan. So, these look the most authentic under bonnet. The shortcomings are that they have no o-ring, and require a little more modification due to a longer shaft. These are my personal favourite despite this.

One word of warning, there are a large number of Accords that have similar D4R83 part numbers, but these have totally different shafts and bodies. These can be identified from having two mounting lugs rather than one. Of course these have the same internals, rotor, etc. and are a useful source of spares - it is from one of these that I got my spare IC ignition unit and a couple of the coils and condenser.

Conversion

For the Nissan distributors, remove the retaining screw (I needed a impact driver on 3 of the 4 distributors) holding the vacuum advance unit, unscrew the advance arm from the 'breaker' plate. Remove the rotor with two flat blade screwdrivers as per the drawing.

Next drive out the roll pin holding the collar, remove the two screws holding the breaker plate, unplug the IC ignition unit from the harness and remove the internals from the distributor body. Clean everything, especially make sure you remove all the old hard grease from the bearings between the two halves of the breaker plate. If the grease goes hard, it can result in the plastic cage that retains the bearings breaking - which is bad news. Regrease and make sure that the advance bob weights move freely and the advance pins run freely in their slots. Make sure you replace the thermal grease on the IC ignition unit - Dick Smith or Jaycar etc.

The next job is to cut off the Nissan mounting flange, which you can do with finesse and a lathe, or almost as neatly with a hacksaw and file (like I did). Clean things, and make it all shinny - I used a soft wire brush, although bead blasting would be better.

Reassemble the distributor, making sure that the breaker plate is aligned correctly with the locating indent in the body. If you removed the stator from the breaker plate, you will need to reset the airgap. The correct gap is set with a 0.012 to 0.020 in feeler gauge between the two tips of the stator and two corresponding rotor tips. You now need to fit the Ford skew gear to the Hitachi shaft. You will find that the Ford skew gear needs to be reamed out to fit the Hitachi shaft (I used a 31/64 drill), then fit the original washer that was under the drive collar and fit the skew gear. Rotate the roll pin hole so that it is at a right angle to the original roll pin hole. Drill a new 3.3mm hole and fit a new roll pin. You will notice that the shaft does not extend all the way through to the end of the skew gear, this is the same as the original.

Now, onto the one shortcoming. As it stands the length of the shaft is such that the skew gear engages 1-2mm less that the original, which was already driving near the end of the teeth. I have checked by looking at the engagement on a spare block and cam, and it does engage completely - this is the distributor that I am currently using, as is - I have had no problems. If you want to be 100% I suggest you pop the distributor body in lathe and spin 2mm off the body, so that the clamp sits higher up the distributor. I do not recommend you pack additional washers between the distributor and skew gear, to gain the 2mm, as the shaft length is already minimal for mounting the skew gear, because the end of the Nissan Hitachi shaft is a smaller diameter for the last 8 mm.

For the Honda distributors, the process (and construction) is almost identical, expect that they have a longer shaft (and different cap and rotor). The 1982 D4R80-34 differs in detail from the 1984 D4R83-18, as the former has a shorter body, with the same shaft length plus a distance piece. The later, has a full length cast body and no need for a distance piece.

Remove the innards as for the Nissan. You will notice that rather than a cast mounting flange, the Honda has a mounting plate that screws to the body. Obviously removing this is pretty easy, but you will need to also apply a hacksaw and remove the small cast mount into which the plate screws. You now need to remove the distance piece from the D4R80-34, shorten the shaft, and fit the Ford skew gear as per the Nissan. Make sure you get the length right, using the original as a reference. You do not need to shorten the casting, as there is a step in the distributor housing in the block (well in the Xflow anyway) which ensures that the distributor does not go too far into the block. This means that when the clamp is fitted to the distributor, it does not need to locate against a stop on the main body of the distributor.

The process for the later D4R83-18 is similar, except that there is no distance piece, and the casting is much longer and needs to be shortened. You can't just cut it off, otherwise you'll cut through the lower bush. What I did was use a Motorcraft distributor shaft which is just a little smaller than the Honda/Hitachi, and the bush from the same distributor as a drift to knock the existing Honda lower bush further into the casing. Once the bush was in far enough I cut through the casting. This leaves a long shaft - which needs to be shortened to take the Ford skew gear. One thing that I noticed was that repositioning the bush means that the lubricating groves in the shaft that lubricate the lower bush no longer go far enough up the shaft. To correct this what I did with this distributor was to extend the helical lubricating grooves very carefully with a hacksaw.

The D4R83-34 distributor was my favourite, since it looks the part under the bonnet with spring clips and all. Now the shortcoming of these distributors is that there is no o-ring fitted. I have had the D4R83-18 fitted for around 1 year, and none of the oil has managed to make it's way out of the engine via the distributor. Next time I'm near a lathe I plan to cut an o-ring groove in both of the Honda distributors anyway.

Fitting and Starting

You can now fit the distributor to the engine in the usual way, engine at the computed number of degrees (Say 7) BTDC, rotor facing number two inlet port, push in and the rotor will end up facing inlet port one. Rotate the body until two of the rotor tips line up with the stator. Look at which terminal the rotor is pointing at. This is number one lead. Connect the leads up in the usual order 1-2-4-3 CCW, attach the vacuum pipe from the carburetor. You will need to make some changes to the wiring. The first thing is to supply the coil from the ignition bypassing the ballast resistor. MKII Escorts and Later Capris use resistance wire, rather than a separate resistor - so don't be fooled, you still need to run a new switched supply wire. I am not sure what MKI Escorts and earlier Cortina's have. If you do use the ballested supply, you will have harder starting and an intriguing misfire. Use the following wiring diagram:

Advance

A good rolling road can set any distributor up on any car to give optimal performance tailored to the exact tune, fuel, and use of the car - but this is expensive.

Status

Since I wrote this article in 2002, I have converted a couple more distributors and run several in my own cars - utterly reliable. The Nissan consumables such as rotors and caps are harder to get than the Honda ones (here in NZ anyway) but once you have new ones, they should last a long time. The only problem I have had is that early on I twice neglected to tighten the clamp up tightly enough, and the timing has slipped in service. Don't forget the thermal grease, it keeps the IC module cool.

An additional caveat, the distributors are taller than the original - this is especially true of the Nissan. The Honda has a smaller cap and can be shortened more easily. I have yet to put one on a car with sidedrafts - not sure about this, but I suspect that there is a Honda with a suitable side entry cap.

My current project involves building the Jaycar programmable ignition, and playing with my distributor curves. Of course you can also do this with a file, epoxy (change the length of the slots in the Hitachi distributor to increase or decrease the total advance) and a handful of springs - but it's a bit more trial and error (read time consuming = expensive dyno time).

Have Fun, Kris.