Distributor options for the MGBGTV8

Gordon Hesketh-Jones (Harvest Gold 1907) from Cornwall uses his car all the year round and with a total mileage now rapidly approaching 400,000 so has a great deal of experience of maintaining the model from his regular servicing work and numerous rebuilds. One regular service difficulty is with worn distributors, so he set about some research into the options for the V8 which he reports on in this note. (Feb 07)

An efficient distributor is clearly at the very heart of an engine and now that our cars are 30 or more years old, age will take its toll. A further problem is that whilst I personally have two excellent distributors both rebuilt by Holden (who purchased all of the rights, tools and stocks of spares for the Lucas distributor range when Lucas dropped out of that business), the quality of the contact sets and condensers now sold - even if they have a famous name on the box - is abysmally low. On my car over the past two years three different sets of contacts have lasted less than 1,500 miles before either developing "pips" or, in one case, the fixed contact stud "un-riveted" itself leading to a very variable spark effect! It seems that, whether I like the idea or not, I have to go for an electronic add-on to the distributor in some form just to get away from the points and condensers. So I set out to explore the market and look at the options.

Starting from basics, the distributor fitted to the MGBGTV8 is the Lucas 35D8 to specification 41394 which is similar to that used on the Range Rover, but with different (faster-acting) advance/retard and bob-weights. A unit to an almost identical specification was also used on the Rover 3500 and 3500S, but a very different specification applies to the SD1. If your distributor has covered more than 100K miles there will certainly be wear on the pinion, the shaft, or the bearings. If any one of these is badly worn or if all three are slightly worn, the result will be erratic firing of the plugs and this random output from the distributor shows up very clearly on a Crypton or similar engine analyser. Even on my current Holden distributor which has done less than 34K miles since the rebuild, the outline of the trace on the Crypton screen is fuzzy and slightly curved instead of being sharp and straight, indicating that one of the three wear points
was probably not replaced - the pinion, bearing or shaft. Note that one of the most common problems with the 35D8 unit is that the advance/retard capsule diaphragm degrades (hardens) over time due to the ingress of petrol vapour so changing this is an easy and cheap action (costing around £25) which you should undertake in any case before looking at other options.

If you are fed up with the problems caused by poor-quality points and the other difficulties, and the screen trace of your high-voltage output is not perfect, the question therefore is whether to go for one of the various contactless distributor arrangements, or to buy a new distributor. It really depends on the mileage and amount of wear on your existing unit. If the shaft and bearings are badly worn, then it may mean that fitting a proprietary electronic kit will not give you all of the benefits you had hoped for, so it is worth looking at the output of your distributor on an engine analyser screen before spending your money.

When fitting any form of electronic kit to your distributor (either opto-electronic or Hall effect-magnetic) which does away with the points, you need to be aware that this will change the character of the advance curve of your distributor. This is because the curve has been plotted with the points in place, so if you take them away then the mechanical load on the shaft and cam is no longer there, and the normal contact bounce no longer affects the movement of the bob-weights. The change might be minor within the generous torque curve of our V8 engines but will normally mean that there will be less advance at lower revs, although in the end the total amount of advance provided should be the same, but at higher revs.

Many suppliers of electronic-assisted distributor kits advocate the fitting of high-voltage coils, but if you do this you will need to change the wiring to your coil. Basically the standard coil is a 6volt device fed during normal running via the ballast resistor; the 12v supply to the coil only cuts in you're your starter motor is engaged, in order to give an extra kick to the coil. There is no doubt however that more than doubling the voltage to the plugs by using one of these high-voltage coils, added to the longer dwell (coil re-charging time) provided by the electronic kits will greatly improve both starting and running.
Comments on the various electronic ignition systems available for the MGBGTV8

On the face of it this London-based firm should be the obvious first choice for an add-on system as they have 30+ years of experience and half a dozen patents, however in the early 1980s I fitted one and it - plus two replacements - and they all failed, so I am biased against them. Their system comprises an infra-red generator (LED) with a photocell receiver and an eight-lobe signal chopper, these three items are located inside the distributor cap, then there is an additional black box containing the electronics to be mounted in the engine bay. The standard kit (which is not for high-performance or racing applications) for an MGBGTV8 costs £168 plus postage and VAT and can be bought from most MG accessory dealers. The high-performance kit (for high-revving), which includes a new coil, costs £258 plus postage and VAT. There is a 12-month warranty on Lumenition products. Incidentally the product name is derived from lumens. In the good old days before the metric stuff came in, "lumens" were the units for measuring the brightness of light so as the first ever product of the company was the opto-electronic ignition. The company name came from combining the unit of light measurement with "ignition". It is worth noting Lumenition now also manufacture Hall-effect distributor kits, but not for our 35D8 unit.

This successful company started making electronic ignition kits for racing motor-cycles in 1969 and most of their business is still in motorcycles plus F3 and classic racing cars, however they make a cheap and simple kit for classic cars which retains the contacts. The unit uses the points to switch the electronics which is in a small box external to the distributor. As the points no longer switch any serious voltage or current their life becomes infinite, and the exact points gap is no longer important. The company is based at Maidstone in Kent, (Tel 01622 730939) and their Contact Assistance Kit costs £29.93 including postage and VAT.

Based in Dudley (Tel 01384 572553) this firm manufactures a wide range of engine tuning kits - much of it aimed at Fast Fords etc but they also are a major supplier and tuner for Caterham Cars and have two rolling road dynamometers for engine tuning. Their "Ignitor" kit fits entirely inside the distributor cap with no external electronics box and is said to give 26K to 27K volts to the plugs with a standard coil, or 30K to 35K volts when used in conjunction with their oil-filled coils. For reference the standard set-up on the MGBGTV8 gives 18Kv. Their system relies on Hall-effect (magnetic) sensors rather than the opto-electronic sensors used by Lumenition. Apparently two types of base plate were fitted into the 35D8 distributor; for the round base-plate the price is £65 plus postage and VAT, and for the triangular base plate £70 plus postage and VAT. Their kits come with a 30 month warranty.

The OPUS unit was fitted to the SD1 from 1976 to 1984 in various forms as they tried to achieve reliability and the final version 35DLM8 with the chip mounted on a heat-sink on the side of the distributor is currently being advertised by Rimmer Bros (Tel 01522 568000) at £235 plus VAT. The Rimmer website makes it clear that these did not come from the vast stocks of SD1 parts which they found in India and recently repatriated, but unfortunately the nickname of OPELESS applied by the trade to these units was well deserved and it should be noted that for reliability reasons the Range Rovers stuck to a version of the 35D8 with conventional points right through to 1982.

This is an American kit using the Hall effect principle that has been in production for a wide range of vehicles for nearly twenty years. Information on their website is a bit sparse but as I understand it they provide a circular plate into which they have mounted eight magnets, with the Hall effect device contained in an epoxy moulding which also fits inside the distributor cap - so no external box is needed. Their early products were for use on VW's then on Porsches so it is no surprise to find that their UK distributor is Maxted-Page & Prill Ltd of Halstead some 17 to 18 miles from Chelmsford, tel 01787 476338 who are Porsche specialists - including racing success at the Le Mans Classic event. Their model number for our car is LU181, price £79.95 +postage plus VAT. Their high-voltage coils work out to £66 plus postage plus VAT.

This firm, based near Malvern (Tel 01886 880101) specialises in the manufacture, overhaul and repair of all types of distributor for UK, European or American vehicles. They can machine up new parts for the Lucas 35D8 etc but their recommendation for all old distributors is to fit their Hall effect magnetic unit which fits entirely inside the distributor cap - no external electronics box is needed but as with all electronic units, there is a two-wire connection to the coil instead of the standard single wire. The standard rotor arm is retained as the "chopper". The unit for the 35D8 costs £93.90 plus £6.00 postage and VAT, and they are prepared fit their kit and also to overhaul your unit if required. They give a two-year warranty on their kits and I like the fact that they do much work for the military, where the requirements for reliability are high.

This was another early pioneer in the transistor-assisted ignition market but they went into liquidation in March 2006 and their assets and designs were bought by Autocar Equipment Ltd
who make the Lumenition range. The Piranha units are now marketed under the name NEWTRONICS; their TO5A kit for our cars costs £66.49 plus postage and VAT and has a 12 month in-car warranty. I understand that in future the Newtronics range will focus on motorcycles leaving Lumenition to cover the car market.


Based in Holland this company has for many years produced new distributors for a wide range of continental classic and vintage cars, then some years ago started to make counter-clockwise kits for UK cars. Their approach however is quite different from the firms listed above in that they dispense with the points-operating cam, the bob-weights and the points box and also the (worn) top bearing. Their view is that it makes no sense to fit fancy electronics which would be triggered by the old cam, which with worn bearings and old bob-weight springs, could have differing moments of velocity at various points in the rotation. They provide two small strong magnets which slip onto the drive pins which previously held the advance weights, and then their ignition kit is simply bolted on. This is a very logical approach, and although the basic system is Hall effect, an LED is also fitted to allow simple static timing. Their kit for the MGBGTV8 will cost £213.00 including VAT and postage. At the moment their kits for the MGB and the TR6 have been on sale for some years and there have been very favourable reports. The V8 version incorporates as standard 16 different advance/retard curves (you can choose which to use using the rotary dial on the base of the unit) and also variable dwell control so that you can vary the voltage developed by the coil. The electronics is also said to incorporate "spark balancing" to equalise the performance between different cylinders. These units are now available from SC Parts on tel 01278 457372.
See sequel on 123 Ignition system (Oct 07) More

This company acquired all of the old stocks of distributors and parts when Lucas withdrew from manufacturing. In the case of our Specification 41394 their stock of parts is low so they will not sell spares for you to do the rebuild yourself - you have to send your unit to Bromyard in Hereford (Tel 01885 488488) for them to rebuild it in their workshops. The current price is £181.56 plus postage and VAT and the workshop time is quoted as being 3 to 4 weeks, although they rebuilt one of mine in ten days when I was in a hurry in 2003.

RPi Engineering/Mallory

This Norwich company (Tel 01603 891209) has built up an excellent reputation for their work on Rover V8s, many of which are used in racing or for extremely fast road use. They offer brand-new Mallory (American) distributors and you have to remember that even today in this oil-starved world, more than half of all the cars sold in America are V8s, so Mallory are in a very competitive market. RPi have already sold over 1,000 Mallory units in the UK and they come in two forms:

Mallory Twin-Contact
he argument for these is that the voltage is shared equally between the two sets of points and they suggest on their website that a mileage of up to 20K miles is quite normal, but I have also heard of various V8 owners having problems with these units. On these units you can adjust the advance/retard curve and the twin-point system provides an extra 10° of dwell time which gives the coil a longer charge leading to a higher voltage to the plugs. Currently this distributor is priced at £245 plus postage and VAT - this price including a high-voltage coil and ballast resistor.

Mallory Unalite or Magnetic - these are complete electronic distributors, ideal for racing and similar applications but rather expensive at £375 plus carriage and VAT.

RPi Engineering
RPi recognised that many customers wanted to have brand new electronic distributors but would try to avoid spending nearly £450 on the Mallory Unalite, so they have just introduced their own range (based on the Hall effect principal) to fit any Rover V8 engine at £175 plus carriage and VAT. This new unit is not yet on their website but has a heat-sink etc on the outside just like the Lucas 35DLM8.

SC Parts Group - the final solution
These people have also come up with a totally different way of solving distributor problems - keep the thing there for the sake of appearance and originality but take away most of its functions. This might sound expensive and complex but the benefits in terms of the engine always staying in tune, of better starting and running and of improved economy mean that this "final solution" should not be ruled out! Basically you would fit an ECU (electronic control unit - a totally normal part on all modern cars) - together with sensors for crankshaft position, throttle position, water temperature, and air intake temperature together with lambda sensors in each exhaust manifold at the point from each bank where the four pipes have joined into one. These lambda sensors detect the amount of oxygen and other gases in the exhaust so helping you to tune the mixture very accurately, whilst tuning the ECU allows you to adjust your advance/retard curve for maximum torque or for maximum power etc. Assuming that the distributor is retained just for sending the voltage (as controlled by the ECU) to the plugs and that the standard coil is also kept in service, then the cost of the parts will be around £700 plus VAT, however fitting the various sensors will for most of us require professional help, followed by a rolling road session to map the ECU properly so the total cost will probably be near to £1,500. For more information contact SC Parts on tel 01278 457372.
The initial posting on the V8BB from Gordon Hesketh-Jones brought a large response from fellow members including:

Chris Armitage: For anyone pondering this I would refer them to my V8NOTE316. In my view the way forward is the Mallory dual point distributor. I fitted it a few years ago, immediately noticed a massive improvement in running quality, and have literally not touched it since! It is a wholly more substantial and better engineered item, but in character with the rest of the car in that there's nothing electronic involved, i.e. if it should ever fail the chances are you'll be able to fettle it by the roadside.

Gordon Hesketh-Jones replied: Yes I did read your V8NOTE316, but the trouble is, there are two separate MGBGTV8s here in West Cornwall whose consistent misfire problems were only cured once they got rid of the Mallory Twin-Contact distributors, so I am not keen to go down that route I would class you as one of the lucky ones.

Mike Russell: I ran a BGT for 10 years with relatively little trouble with points other than a general reluctance to start but I've found that goes with the territory. I bought my current MGBGTV8 in 1997 with a Lumenition unit fitted, but the records I inherited do not include a receipt or date when it was fitted. However it has performed faultlessly for 10 years and I have never had occasion to 'fiddle' with it. Turn the key and off you go. Mind you I do not clock up the kind of mileage Gordon does, but if I bought a car without electronic ignition it would my very first purchase closely followed by halogen headlights and then a battery conditioner unit.

Graham Cornford: My MGBGTV8 has the original Lucas distributor. I have a Pertronics electronic ignition system that fits totally within the distributor cap with the exception of a lead to the coil which has been changed to a Pertronics flame thrower coil. I never touch the distributor. It always starts well even after a long layup. The only problem was that at first there was a problem with the tacho. It read backwards. That was solved by Speedy Cables. I know of another later unit that has been fitted to a V8 and that one had no trouble at all. It was realistically priced, about £50, unobtrusive and works well. It came from the USA but I believe that Pertronix have an agency in the UK. It is thoroughly recommended. The plug points gap though has been increased to 45 though to make the spark really jump.

Tim Edmonds: I have had a Lumenition system fitted for over 15 years to my MGBGTV8 as I also got sick of replacing the points and the plastic adaptor had failed.

Gordon Hesketh-Jones responded to Mike Russell and Tim Edmonds: My problem with the Lumention unit is the THREE of them have failed on me and I really don't want to try "fourth time lucky"!

Nigel Melbert: I would like to confirm Graham's comments as I also run a Factory MGBGTV8 with a Pertronix Ignitor 2 electronic ignition coupled with their Flame Thower 40,000 volt coil having removed the Luminition unit. Currently it has covered 10,000 miles without a hiccup, starts first time every time no matter what the condition. I had the earlier unit fitted to an 1800 Roadster which covered more than 30,000 miles without the distributor cap ever being removed. I think that this is one of the best and neatest units on the market and at approx £50 to £60 is excellent value for money with a two year guarantee. I have the original publicity blurb if anyone is interested. I purchased both items through www.lbcarco.com/

Chris Armitage returned with additional information regarding his advocation of the Mallory distributor I have to confess that I have mine set up in single point mode rather than dual point! I bought the Mallory unit from RPM in Norwich, who have detailed instructions on how to set it up on their website. Lacking a dwell meter, I found this a bit daunting so disconnected one point and set up the other as per a standard distributor. When I have more time and a dwell meter I will set it up 'properly'. But even with the single point, the size of the contact set is at least double that of the flimsy Lucas item, and is clearly much better made, and the condenser is again at least twice the size of the Lucas equivalent. Everything is engineered on a grander scale, there is no slack in the mechanism and the amount of advance is adjustable.

If the examples Gordon has quoted suffered from miss-fire I would venture to suggest that maybe the dwell of the 2 point system was not set up properly. If you operate in single point mode then there is no feasible difference to the Lucas set up, except that the spark happens at exactly the right point in time rather than scattering all over the place. This was first apparent to me when the strobe light indicated a rock steady setting rather than the blurr previously, and this was reflected in the running quality. Get a Lucas distributor in one hand and a Mallory in the other and you will never want to put the Lucas one back!!

Chris then added he has no connection with Mallory or RPi and the distributor is the only non-standard bit of the car. He used to have an optical Luminition system on the previous Lucas distributor but it suffered from misfire which went away when I replaced the manual points. Finally, replacing the points with electronic ignition on the Lucas distributor is only solving half the problem, as you still have all the slop in the mechanical advance mechanism and have to keep replacing the vacuum advance unit frequently - or at least I did.

James Heaton added some comments: I have done about 60,000m in my MGBGTV8 in the last two and a half years. The car came with Piranha which died after about 25,000 miles on a wet, dark, wintery night - as they do. I fitted a Lucas Opus 35DLM8 bought from Rimmers and as I was away abroad on business, took the opportunity to upgrade the oil pump to increase its capacity and pressure. I have run with the Lucas Opus for about 35-40,000 miles without a problem. Having said that the first unit received from Rimmers was faulty but they happily changed this. I know that Clive Wheatley sell these and know he would not do so if he had doubts about them. My previous car was a Rover P6B, 3500S fitted with Lumenition and this worked faultlessly for three years and 90,000miles.

Ph-A Kaplan from Antwerp in Belgium added: I have been on the side of the road on Saturday night so I changed to Lumenition. It works faultlessly. Done 6,000 miles since with a mixture of weekends and mixed urban/highway motoring. He added a comment on the oil pump: I am quite interested in supersizing the oil pump. I do not know what the exact pressure should be, but as I have a heavy right foot and my V8 is quite willing to perform, I would like to go for a larger pressure/ flow, so as not to harm her. Could you advise me what/where to buy from?

Gordon Hesketh-Jones responded: Reference the query from Ph-A Kaplan about oil pressure and whether to change the oil pump, the V8 engine will only have had a pressure of 42psi when brand new. If your engine is showing better than 39psi at say 3,000rpm when hot, then it is OK. Fitting a high-pressure oil pump will not help the bearings.

To be continued . . . See V8NOTE379 (20.6.08)