John Harris

I have had a 123 dizzy in cars for the last 15 years or so, in a Spitfire and MGB GT V8. I have had one failure when an alternator diode failed and put nearly 20v across the dizzy. The failed dizzy was replaced by Southern Carbs. I have had no coil failure from them.The alternator on the Spitfire and MGB put out about 13 v when running. Problems I have seen in other cars fitted with them have arisen from two problems - poor spade connector connections on the low tension side leading to intermittent firing - this is the fault of the installer, and secondly poor fitting of the ignition leads, particularly the coil lead not pushed home enough either on the coil or dizzy cap. If all of the above are ok the only other problem I have seen is incorrect initial timing with the green light coming on at TDC or the advance at idle in the program being set incorrectly ( sometimes in combination with the vacuum advance settings ). If it is a 123 dizzy with 16 pre set curves then in most cases the car will start which ever program is selected as long as the initial timing is ok, obviously it might not run well through the revs if the incorrect pre set program is used, but it will run. If fitted correctly and there is a spark at the plugs but it is not firing, or fires then fails, then it has always been a fuel/carb problem. I have used them with standard coils, sports coils and flame throwers. The MGB is used extensively on track days and European trips, so no shortage of vibration and heat cycles. The Spitfire recently went to the South of France. Happy to come and have a look if it helps.

Pete In the opening paragraph I did say coming down the rev range. From maximum advance down. And yes is does complicate matters, that's why a conventional dizzy is designed with an operating envelope because most of the time it will not be timed properly, and so is designed to work OK, but not optimally unless properly times. And I did not seek to replicate the WSM, just to point out that a standard dizzy, whilst OK, can be made to run better, but needs some skills to do it, the same skills needed for a programable ignition.

I don't have one, but a friend of mine uses one when tuning twin carbs. He sets them and then double checks the temperature at the jet/needle intersection and insists that they must be with 1/2 degree of each other and that therefore ensure better accuracy/evenness of the mixture in each carb. ( airflow etc is all checked and even ). From the colour of the plugs they seem exceptionally even. Not tried it myself but am going to on my spitfire. Has anyone else done this ?

Apologies in advance for the long post. A set of points, with a fully reconditioned dizzy, using standard weights and springs and properly timed is not optimised ignition. It is a manufactures operating envelope that will work well in most conditions and allows for the fact that most garages back in the day could not or not be bothered to set dwell angles and timing accurately from a work shop manual. Anything set just statically to BTC or dynamically at BTC will not be accurate, the tick over of the engine will not allow very accurate measurement. That is why in a good work shop manual the measurement is given at RPM points and must be measured coming down the rev range and should be checked at the point from maximum advance down. Most garages would not do this. You can find the advance graph for a dizzy online, with the advance at set rpm through the range. Indeed many of them have a +/- 2 degrees or so at each point and you can plot the envelope. To optimise for this you would still need to know what you are doing with at least a programmable strobe. With this technique, you could optimise for the advance for the particular weights and springs. This would not be the optimised advance curve for the engine. That's why racing engines were set up on a dyno with the tuner testing different weights and springs. A conventional dizzy can never be optimised in a production car, the graph alone is governed by the weights and then the point at which the secondary spring comes into operation and the cut off point for maximum advance. Elegant in its day, but when fuel efficiency was needed mapped ignition came to the rescue. They are not curves put two straight lines as the first springs takes precedent before the second one comes into operation. Fuel injection and engine management overcame this problem. Taking a programable ignition, entering the advance graph for the conventional dizzy and timing on the engine in the conventional way is not complex or difficult. It will of itself be an improvement on a conventional dizzy because its frequency of spark operation is far more consistent. Anyone who has seen even a new dizzy on a test bed under a strobe will know their variability in comparison with an electronic system. I completely agree that fitting an electronic pick up to a convention dizzy brings no advantage other than not needing to change points. If properly timed as above, then at least it should relatively be fit and forget and remain accurate. Having bought classic cars with these fitted - my current spitfire included, I find that most of them have not been properly timed. If you added an electronic pick up you have to ask yourself did you properly time it or just set it at static or dynamic BTC. If that is all you did it is not running optimally for the weights and springs in the dizzy. To optimise for a conventional dizzy then every time points are changed the correct timing procedure must be gone through. With an electronic pick up this only needs to be done once. With a programable ignition, the torque and bhp can be properly optimised, and this will enhance the driving experience. I accept the cost issue, but before fiddling with fuel or filters etc then at least properly time a conventional dizzy. A programable ignition is not a must have. To get a car operating properly a must do is to have a properly operating conventional dizzy timed properly, which is more work than setting it statically or dynamically at BTC. Lots of members will have a strobe light, so having got data for the graph, could measure at a set rpm ( probably no more than 1800 rpm ) against a timing mark, this will be more accurate than just setting dynamic timing. The strobe light/timing mark will be steadier. Those that have a programmable strobe can test the curve all the way from maximum advance down. Those that are capable of doing this will manage a programable ignition easily. A conventional dizzy, points or electronic pick will make a car run well, provided it is truly properly timed and in good condition. Anything with old springs and weights is unlikely still to be following the ignition graph well.

Lets just deal with some facts. To get the most out of a standard engine ignition timing must be fully optimised, carbs set optimised, this assumes everything else as per the specification. The first statement - ignition timing fully optimised cannot be achieved with a standard set of points, with standard weights and springs. So the first point of performance improvement should be ignition timing. ( I won't enter the debate, but I use a programable 123 - other solutions are available ) Second step to performance is get more fuel and air into the engine - K&N filter do do this, side by side rolling road test show this, it is modest perhaps 5 %, little bit more if the exhaust is optimised for flow - up to 10%. Torque a little bit more perhaps getting on for 7%. Yes you have to change the needle - AAQ/AAT for a 1500 would be the richer needle. I accept the cost/performance argument but K&N will provide an improvement assuming all the other steps are done first. If I was to spend money, I would always start with the ignition before anything else. You can see an improvement on a rolling road throughout the rev range immediately.

I have adjustable front wishbones, so run about 1/2 degree of negative camber. This will be fine for road use and for a wish bone suspension will keep the tyre in better contact with the road as it comes under load when cornering. Even with longer shimming bolts I am not sure I would shim all the way to negative camber, you are transmitting a lot of force through the distance of the wishbone end, through the shims to the chassis. From memory that's a lot of shims. The Castor angle on a Spitfire should be about 4.5 degrees, but these vary quite a bit due to manufacturing tolerance and can be quite different on either side. I have not been able to alter it by shimming. Less castor angle will make the steering lighter and have less return to centre after cornering, and will feel less stable in a straight line. More castor angle will solve for this, and keep more negative camber when cornering, but means heavier steering - hence power steering on modern cars. As said previously, when setting up a car such as my 1500 spitfire, I did it with weight - 120 kg - in the vehicle ( two people ), a full petrol tank. I also have adjustable trailing arms, so no shimming, and can be adjusted along with the wishbones whilst on an alignment system. ( plus lowering block to set the rear camber angle correctly ) I have an MGB V8 which I have also put negative camber into the front suspension - 1/2 degree achieved by offset bushes. On it I have increased the castor from 7 to 11 degrees by putting wedge shims into the front cross member to maintain more negative camber when cornering, but have added electric steering to compensate. The offset bushing method may work on a Spitfire too, but some calculations would be required first. If they would then better than shimming but not as good as adjustable wishbones.

Before you could buy them I made mine from UHMWPE for fitment to as new spring from an exact set of measurements that I got of the net. The Dutch club made some, but they were too thick if I remember correctly - I did get some to check

I know I a am a bit late to this post but if you have not solved for it I can send you a good starting 123 ignition curve with the correct vacuum advance element. Used on my spitfire 1500. If for your engine you have higher compression than standard you might need to reduce the advance slightly after 2000 rpm. Also do not just rely on setting it with the green light, once you have fitted the 123 and got it running pick a reference point at say 2000 rpm and use a programmable strobe to set that at TDC it will be much more accurate. I have a standard 1500 ( 1980 ) with K&N air filters and appropriate needle. Flies round to 80 MPH no problem, yours should be even quicker. As the previous post says, a rolling road will do the trick. I also have an MGB GT V8 with a 3.9 high compression engine that I have just fully rebuilt. That was put on a rolling road with a programmable 123 - done at Northampton Motorsport - I live just outside Brighton.

With regards to my earlier post, I have a 1500 standard spitfire. Used extensively, including trips to the south of France. I have attached the 123 ignition curve I have programmed. This was copied and adjusted from a Mega-jolt map posted on the web for a 1500 spitfire. I know lot's of you will look at it and say, "way too much advance" but it runs really sweetly. Lucas sports coil and 35 thou NGK plug gaps. Having installed the 123 I checked the timing at 2000 rpm and adjust to the ignition point I have for that in the curve. That process ensures greater accuracy. I have a programable strobe. You could experiment with weights and springs in a conventional dizzy to get a similar shape, but as said earlier it will be a best average.

I have run 123 programable systems on my spitfire for the last 5 years and on an mgb gt v8 for 10 years. No failures, much better torque through the rev range if you understand how to optimise them. Once set, they have been utterly reliable. Rebuilding my V8 as a ground up restoration at the moment, even the engine builder recommended a 123, that engine is being set up on a dyno before being installed. No comparison to mechanical dizzy, even with electronic/optical pick up, much smoother too.

On a switchable 123 ignition you time it at TDC, the green light comes on, and therefore the curve given in the instructions is already the total advance. When you have installed the 123 then re-time it with a programable strobe at say 23 degrees at 2000rpm, as per the choice of curve, it will be more accurate than static with the green light at TDC. I run a 1500 spitfire with a programable 123 and have found that it will take more than the max set out in the WSM. I developed my curve from a mapped ignition system published on the internet and then adapted it. My 1500 is standard with K&N air filters, yellow carb springs and slightly richer needles for the K&Ns, original engine, 75000 miles. I attach it for comparison.

Harry Below are two articles to read. The first gives the basics, the second the data you need. http://auskellian.com/paul/links_files/performance_enhancements.htm - Basics http://auskellian.com/paul/links_files/springs.htm - suspension data Be careful with spring suppliers. Moss and Rimmer Bros quote spring rates of 150 Lb and supply springs with 12 coils for 1500. On a 1500 with standard shocks, including Koni's it will become coil bound. SC parts quote 180 Lb and 11 coils, works much better. If you want to lower the suspension you will need a higher poundage and less coils combined with a short action damper. The articles talk through the geometry front and rear. I run SC parts 180 Lb on the front with Koni shocks, shimmed for negative camber. On the rear I run a standard leaf with a compression/lowering block, with UHMW polyethylene thrust washers made to the spec in the article with Koni dampers and adjustable radius arms. I also have an MGB GT V8 which runs Gaz rear shocks. Koni and Gaz both work well. Not too hard on the lowest settings.

Luke No problem, sorry to hear that's the case but I understand, if it does not sell drop me a note and I will help you get it going for a better sale. John

Luke How is your car ? it might be possible over the next month to get you going now lockdown restrictions are easing. Let me know your thoughts

Thank you, much appreciated. I knew I had seen them somewhere, I looked at their adjustable radius arms, but bought them from Rimmer's in the end. John

I am inducing some negative camber in the suspension, and in doing a set of measurements note that the castor angle is only just 2 degrees on the near side wheel. 4 degrees on the off side. In calculating the shimming to push it back to the correct 4 degrees I think there is just enough thread on the stud, however, to be sure if I can get ones with longer studs I would. I have changed the front springs from 167lb from moss ( for a 1500 spitfire ), to 180 lb from SC parts. The former had 12 coils and a shorter free length, 7.5 inches when compressed, but were coil bound. The 180 lb are 8 inches when compressed and have 11 coils. The car now drives much better. However, the new springs, even after settling have induced some positive camber and I want to push it back to negative. John

I have a spitfire 1500 and I need to buy lower wishbone brackets with longer studs going through the chassis rail so that when I shim them there is ample thread for the nut. In particular I need the rear bracket to have a longer stud. Does anyone know where I can get them, I have seen them advertised before, but seem unable to track any down now ? John

Unless I am missing something in the photographs the 15 thou gap does not correspond to the peak of the cam on the dizzy ? But may be I am missing something in the photo ? If my interpretation above is correct, then the dwell angle will be out and the capacitor may not get enough charge to discharge enough current through the coil, and thus not creating enough HT to spark across the plugs, and then when it starts running and is under greater pressure, hence it stops after 20 seconds or so. I agree that it should start with the timing out, however, if the time to charge the capacitor is restricted less discharge across the coil will happen and a lower HT voltage, meaning it will not jump the spark plug gap. Be sure that the 15 thou is at the top of the dizzy cam and then the gap opens at the static point before TDC. If the picture is meant to show the point at which the points open and the static timing marks my apologies. Nonetheless, I once had an engine ( midget 1275 ) display the same characteristics, three capacitors later it ran fine !

I have done it on a 1500 spitfire, wide radiator, I replaced a blower Kenlow fan so no original fan to remove. Initially you might think it will not fit, it is so finely engineered, but it does and it works every well. I flushed out the cooling system, prior to installing, with a flushing agent and then hosed through. The car went to the south of France two years ago in the middle of summer, no issues with cooling on the motorways or up alpine passes. In fact the fan only came on when stationary after a long run, but returned quickly to normal. The car kept a steady 70MPH on the motorway.

Luke Keep the battery charged, then when we need to get it sorted we have power, something like a CTEK device. Catch up when lock down is over, I was working on my spitfire today and my two sons gave me a hand and then took it out for a test drive.

Luke, I live just outside Brighton and have a 1980 spitfire. When we are allowed to move again I am happy to come and get you going, I have programable strobe, air flow meter, plus other tuning tools. We can work through ignition timing, then fuelling and tuning, get it going well with the bits you have on it and you can have a go at doing the changes and learn in the process. John