Mustang Sallys Land Rover Pages

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Mustang Sallys Ignition Saga

• My 109 has a General Motors/Holden 3.3 litre (202 cu.in.) six cylinder engine. When planning the installation, I always intended to fit an electronic ignition module built from a kit of parts. This is really just a transistor-assisted ignition which retains the points but uses them only for triggering rather than as a switch for heavy coil current. The design  was developed by an Australian electronics magazine and is described more fully on the Electronic Ignition page. Its use of a fixed duration spark and an extended "dwell"  time for the coil gives a higher energy spark at all engine speeds. An ordinary ignition coil is used, in my case a ballast-resistor type from Bosch.

• The distributor was also a Bosch and I'd taken it apart, verified that the shaft bearing bushes were in perfect order, that the centrifugal advance unit moved freely and that the vacuum advance capsule was working. The electronic module was built, bench tested and installed. This module also has input circuitry for a Hall-effect device or a reluctor-type trigger found in more recent distributors. The Bosch ignition catalogue lists a Hall-effect trigger and interrupter vane which can be retrofitted to older Bosch distributors but I thought that the points type triggering would be good enough for me.

• I settled into a debugging and refinement period after the Land Rover was registered for the road. It went well enough, though I thought it seemed a little unwilling to rev. I put this down to its state of tune as a later de-toxed version of the Holden Red six.
  Then came the ignition dèbacle described in A Text-book case.  I began to wonder whether I should try the ignition advance curve used in the earlier pre-emissions law version of the 3.3litre engine. The  advance was restricted in the later models, though precise details aren't easy to obtain. Later Holden 3.3's also had a gearbox switch to allow vacuum advance only in top gear, only after the engine had reached operating temperature and only six degrees of vacuum advance in any case. There is no such gearbox switch in my Land Rover so I'd already abolished the top-gear-only restriction and fitted an older vacuum capsule which permitted more advance under part-throttle/light load conditions.. I find, by the way, that vacuum advance capsules are no longer made for those Bosch distributors so I am adding every serviceable one I see to my lifetime supply of spares.
  Well, I gave my distributor to the local Bosch service depot and explained how I wanted it to match the advance curve used for the earlier engines. When I collected it again, I learned that the centrifugal advance mechanism had been totally worn out. The technician showed me the two bobweight pivot pins he'd replaced. They were worn nearly half way through. Though the unit looked and moved OK when at rest,  a run on the distributor test machine showed the bobweights sticking and binding on the pivots which restricted the advance very badly. After repair, the mechanism was adjusted to the desired advance curve.

• After refitting the distributor, the difference was stunning. Acceleration through the gears was very noticeably better and highway fuel consumption improved by three miles per Imperial gallon. The comparatively small bill from the Bosch serviceman was money well spent, as I'd learned that centrifugal advance units can look alright and still be totally unserviceable. Something to keep in mind when working on other old klunkers of any make.

• This should have been the end of the story, except that I still wasn't happy with the performance of the points. Sure, they did not burn or pit because they were only being asked to trigger the ignition module while passing just enough current to keep them clean. However, the rubbing block still wears so that the points gap needs readjustment at intervals. Not the "set and forget" system I was hoping for. 

• But there is hope for any Holden Red six, in the form of the Bosch breakerless electronic distributor fitted to the VC and VH Commodore "Blue" engines from 1980 to 1984. The abolition of points came to Australia somewhat later than in the USA where breakerless ignition in domestic cars dates from the early '70s. The Bosch reluctor type distributor was used for four years in Holdens and a nearly identical one appeared in contemporary Ford Falcons. In 1984, the VK Holden Commodore featured the final black-painted version of the ancient red engine with either an Electronic Spark Timing engine management system or the full Bosch Jet-tronic EFI.

• The beauty of this Bosch breakerless distributor is that it will fit any Holden Red six from the 1963 EH model onwards. It is a popular conversion for older Holdens because it gives slightly improved economy, a slightly smoother idle, better starting in adverse weather conditions and is virtually maintenance-free. Unfortunately, its desirability is reflected in its price and scarcity. A perfect Economics 101 illustration of the Law of Supply and Demand!

• I got mine over the phone from Barsby Spare Parts in Maryborough, Queensland, a firm of specialist Holden breakers.  The thing was purchased, sight unseen for $180 Australian and arrived in the mail a few days later. The price was right, according to the word on the street, and I got exactly what I was promised; a used Bosch electronic distributor in clean condition, in working order with new shaft bushes fitted and including the correct Bosch ignition coil. A very satisfying buying experience and well worth a mention in the Links section.

Description and Fitting

• The electronic distributor is somewhat larger in diameter than the one it replaces and the distributor cap and rotor arm are of different dimensions. The High Tension lead terminals on the cap and ignition coil are male fittings resembling a spark plug top rather than the sockets found on the points type distributor so a new set of plug leads is required. The distributor does not have electronic advance. It has a centrifugal advance unit hidden away below the reluctor assembly and a vacuum advance capsule acting on a moving plate carrying the pickup stator. These need to be checked for serviceability. I recommend a checkup by a distributor specialist if in doubt.

• The pickup stator consists of an iron ring a couple of inches wide with a coil of wire of about 1000 ohms resistance wound around it. The inside of the ring has six triangular "teeth" spaced 60° apart. The rotor or reluctor is an iron vane with six similar teeth keyed to the distributor shaft and rotating inside the stator. The peaks of the reluctor teeth pass very close to the peaks of the stator teeth every 60° of  reluctor rotation. Every time this happens, the magnetic field surrounding the pickup coil changes and a voltage pulse is induced in the wire which serves to trigger the electronic module. As the moving parts never contact each other, the ignition triggering components don't wear or need regular adjustment.

• The electronic module hides on a platform under an easily removable metal dust-cover on the side of the distributor base. It is an anonymous looking black plastic oblong with four screw terminals. The leftmost ones marked 3 and 7 go to the reluctor pickup coil inside the distributor. The one marked 16 goes to the negative terminal of the coil. The one marked 15 is the power terminal for the module and goes to +12 volts from the ignition switch. This switched 12 volts can be conveniently found at the positive terminal of the coil. If your previous ignition coil was a 7volt type fed by a ballast resistor, the ballast resistor must be bypassed as the the breakerless coil needs the full 12 volts.

• The plastic module should be firmly screwed down on a smear of silicon heatsink compound as it contains the high current switching transistor which turns the coil primary current on and off in place of the conventional points. Information about this electronics module is scarce but I gather that it uses the same fixed duration spark/extended dwell concept as the box I made.

• The fitting of this distributor to the engine is similar to the procedure for replacing the original points distributor.

• When preparing to remove the old distributor, remove the distributor cap, take all the sparkplugs out and turn the engine until No.1 cylinder at the front is at TDC on the compression stroke with both valves closed. The notch on the crankshaft pulley should be in line with the longest timing mark on the pad cast into the front of the engine. The rotor arm will be pointing at a faint scored line on the top edge of the distributor base which indicates the firing position for No.1 cylinder.

• If the rotor arm is not pointing at the No.1 mark, the engine is not at TDC for No.1 cylinder. But if all is OK, remove the clamp piece and bolt at the base of the distributor and withdraw the distributor, noting how the rotor arm turns clockwise a little as the helical drive gear unmeshes from the gear inside the engine. Do not disturb the engine from now on or you will have to find TDC on No.1 cylinder again.

• On the new electronic distributor, look for the faint scored line indicating the firing position for No.1 cylinder. Rotate the distributor shaft so that the rotor arm is at about the same position clockwise from the line as the rotor arm was on the old distributor when you were completing withdrawal. Slide the distributor into the engine. As the gears move into mesh, the rotor arm will move anti-clockwise to finish up pointing at the No.1 firing mark. You may have to try again if you miscalculated on the first attempt. Replace the clamp piece and bolt and do it up lightly. Turn the engine anti-clockwise slightly so that the pulley notch lines up with the 6 degree initial advance line on the crankcase. Rotate the distributor slightly so that the six points on the star shaped reluctor rotor line up with the six points on the stator ring. Tighten up the clamp bolt. You now have an initial setting sufficient to start the engine and refine the timing further using a dynamic timing strobe light.
  

Ignition Coil

I received the correct ignition coil with the distributor. However, I tend to be suspicious of second hand coils. The Bosch catalogue lists a replacement coil HEC716 for electronic ignition which I purchased. This is quite unlike the oil filled coil originally used, being an epoxy potted "transformer" coil wound on an E shaped laminated iron core. It has a mounting bracket supplied which suits the original mounting point on the side of the engine. The original connecting leads attached to the distributor fit straight on to the terminal hardware supplied with the coil.

In Service

The new distributor was fitted as described and the engine started on the first turn of the key. After refining the timing, the engine seemed to idle more smoothly and the performance was comparable to the reconditioned points distributor with home-built electronics box. In both cases, the coolant temperature is a couple of degrees lower than it was when I first put the Land Rover on the road. This will be because the spark is no longer chronically retarded. I carry the safely wrapped up points distributor and plug leads in the toolbox for fitting in the unlikely event that the electronic distributor fails miles from anywhere. The points-type coil remains fitted in the engine compartment.

According to the designer, my home-built electronic ignition box can be driven by the reluctor pickup in the new distributor. On the other hand, the Bosch module seems to do the same job and is neatly integrated with the distributor so I'm not inclined to experiment just at present while everything is going well.

For what its worth, here is a table with the part numbers for the electronic distributor.

 

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Legal stuff: These pages have no connection with Land Rover, BMW or any of their authorised agents. The information presented herein comes from my personal experience and I guarantee the veracity of none of it. Visitors should exercise their own judgement and seek expert advice about local vehicle laws before applying any of my practices to their own vehicles. The fearsome copyright notices seen on some web-pages probably aren't worth the bytes wasted on them. If you want to rip off any of my stuff for non-profit purposes please let me know and give me credit.