LUCAS DISTRIBUTORS, WHY THEY NEED TO BE REMAPPED, TO CORRECT THE ORIGINAL MAPPING PROBLEMS AND TO RUN WELL WITH TODAY'S FUELS.

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Most of us now drive Twin Cam 4 valve cars without even knowing, or caring what is under the bonnet. Manufacturers are totally interested in efficiency, emissions etc, as well as power, torque and smoothness. Even the “El-Cheapo” cars are wonderful compared with the lousy cars that we had in the early days of driving. Then a Twin Overhead Cam 2 valve engine was a car to drool over, or a racing car. 

In the 70’s, with the world wide need to make fuel efficient low emission engines came new ignition systems, fuel injection, high compression etc. With the huge improvement in engines came an equally big improvement in fuels, to operate these engines. Who would have thought that cars would run 10 to 1 or higher CR with 91 RON fuels, back when the MGB pinged at 8.8-1 CR, unless Methyl- Benzine was added to the normal Super Grade fuel.

As fuels changed so did the mapping of ignition systems and air/ fuel ratios to minimise emissions and improve economy. This leads into what I want to say regarding the necessity to re-map all old distributors [PARTICULARLY LUCAS] to operate properly with modern fuels, which have very different burning profiles, [they need less low end and midrange advance and less overall mechanical advance], to the fuels which were available when the MG was a common sight on our roads. 

I have known of this problem for years, but who would one trust to try to re-map the advance curves of a distributor on a 30 to 50 year old car using a simple points and capacitor ignition system. 

I tried to get the “C’s” distributor remapped when the problem became so bad that even on 8.6-1 CR, that I was using, the car would not run well on 97RON fuel. I had previously used BP100 or 100/130 Avgas for years until it was no longer easily available. I took the distributor to Kevin Baker [Beam Electrical] and Kevin tried to get it to conform to the workshop manual settings, which were vague and very imprecise anyway. This allowed me to just run on 97RON fuel, but pinging around 3,000 RPM was still critical under power. The distributors in the early “C’s” had the wrong advance springs fitted, by guess who, LUCAS. The correct springs were written up in “Safety Fast” magazine in August 68 but were not available here, or the UK, by the time I tried to locate a set. I expect that they were all snapped up by UK “C” owners, or replaced under warranty in the UK. My car was the only “C” in Australia until 1970 and the “C” ceased production in late 69 early 70.

I just accepted this and put up with it, not knowing what to do or how to do it. A few years ago I was looking at the MG Motorsport web site [UK] and was surprised to see that they were claiming that their fast road engines in “B’s” and “C’s” ran well up to 11-1 CR on 95RON fuels with their re-mapped distributors. I E-Mailed MG Motorsport [they refused to provide any information on this remapping or to supply spring sets etc.] and they replied that their re-mapped distributors were available for 65 Pounds on an exchange basis only. Too long away and much too expensive in AUD plus air freight both ways and ‘X’ weeks off road with no guarantee that the distributor would not go missing. 

While buying “EBC” Green Stuff pads for the “C” I talked to Steve at Greg Tunstall Mechanical, at Cleveland, about the problem with the Ignition and he said, “The first thing Greg does when he rebuilds a Triumph or any motor with a Lucas distributor is to send the distributor to “Performance Ignition Services” in Victoria, to be rebuilt and remapped for use with the current fuels. 

This resulted in me contacting Dick, the owner of Performance Ignition Services, I asked how long they had been servicing Lucas distributors and he said “I have had the business for 25 years. I bought it when the original owner retired and he set it up 25 years before that”. So here was a company that has been rebuilding and remapping distributors for 50 years. To add irony he said we are about 50 metres from the Victorian MGCC clubrooms. Dick says that when the MGA Twin Cam engines are remapped that they will never burn holes in pistons again, it would seem that the real problem with the Twin Cam was not the cylinder head design or the compression but the ignition mapping was all wrong right from the start, just the same as the MGC. [It is no surprise to me that the UK lost their Motorcycle and Car industries to countries that could and did do their engineering homework properly]. The MGB-V8’s also benefit from remapping, as would all MGA’s & MGB’s. I would expect higher compression X-PAG and X-PEG motors would all benefit from having current knowledge applied to get the best results, from current fuels, or just to have the mapping correct for the first time. Lucas did not pay a lot of attention to accuracy or precision in their designs, cost was always the primary motivation, if it worked that seemed good enough. Fortunately Bosch did pay attention to precision, cost was secondary.

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I discussed the problem with the distributor. Dick said they knew all about the mapping problem with the MGC. I mentioned this to a friend in the GCMGCC who has a C-GT. He then sent down his distributor [this unit was not even a “C” distributor but a Lucas Australia 6 Cylinder without vacuum advance] to be rebuilt, with electronic ignition and remapping. A group of GCMGCC members then went for a little tour to Karumba, on the gulf, and back to Maryborough a distance of 2,000 miles. The C-GT on 95 RON fuel got 30.8 MPG. Standard MGC-GT’s do not run on 95 RON fuel and certainly never get 30.8 MPG and this car is Air Conditioned as well, he is very pleased with the result.

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So I then decided to send down my distributor to be rebuilt and remapped, I already have a Lucas electronic ignition kit in it. When it came back I fitted it and timed it to 10* BTDC as instructed. Whammo a whole different car. For the first time ever the idle was smooth and at constant revs, not plus and minus 200 RPM around 800 RPM as it used to be. Much improved low down torque, and power from 1,500 to 2,000 RPM.