John Hugh1 April 2013 at 16:51 #50096
Has anyone experience of using coil ignition on a 2 litre? After endless magneto bothers (despite expensive rebuilds) I’ve fitted a coil conversion that uses the ubiquitous Bosch 009 distributor. Usual practice with a 2 litre is to start with a little manual retardation then whack it straight up to full advance when it fires. The advance curve of the distributor is such that full advance (set to 36 degrees) is only reached at about 2500 rpm from about 15 degrees advance at idle. I’m concerned that spending more time with less advance may cause an engine that already overheats at the drop of a hat to overheat even more easily.ray sherratt1 April 2013 at 19:47 #50097
Is the old mag auto advance or static, if auto and you know
the curve of the old unit, then the Bosch unit can be calibrated
to suit.You could have slight retard to start.
Distributor doctor is a good man discuse it with him.
Ray.John Hugh2 April 2013 at 21:50 #50098
Thanks Ray. The old mag is static so there’s not really a curve in normal use. Just a little manual retard to start and preserve the bendix, then straight up to max advance. I suppose this could be imitated on the distributor by mucking about with the springs controlling the centrifugal weights but I’m no expert and that worries me. Thanks for the URL, this could be the answer.
Johnbill3 April 2013 at 07:12 #50099
John, if all else fails a very simple solution is to convert your original magneto into a distributor – if it is a type which makes this possible. Take the mag coil out and put an HT lead in a holder in its place. The HT lead goes to a modern coil (tucked out of sight) and condenser. I did this mod on my 3 litre (Scintilla mag) and it cured all the starting problems (always a bit marginal on the 3 litre as the mag goes at 3/4 engine speed). It is then easy to carry a spare coil and condenser – just in case. This does not really affect the original look of the engine bay as you still have the mag in place -as long as you can hide the modern coil out of sight. Much cheaper option than fiddling around with mags !John Hugh4 April 2013 at 10:18 #50100
Thanks Bill. I had thought about converting the mag to act as a distributor but mine (Bosch FF4) uses the wound armature and I reckoned I would need to butcher the thing a bit to make it work and that I don’t want to do. Incidentally, why did manufacturers not all adopt the Scintilla rotating magnet approach? It would seem to be so much simpler and better a design.
JohnPeter S3015 June 2014 at 13:55 #50892
I mentioned I had recently trouble with the magneto ignition (BTH GA4) on my 2ltr LC. During a drive it failed and only gave some rare misfiring. I did put my spare coil ignition in instead (I now also have the adaptor piece to be able to use the clamp of the magneto without change). It has no advance-retard options but worked fine to bring me home. The complete unit (without the distance piece adaptor which I made from wood and painted black) is supplied by club member John B29.
Later with the magneto on the living room table I found the simple and stupid reason: the contact breaker distance had become to small (below 0.2mm) and the cam-ring which is operated by the advance-retard lever had some play and probably had tilted a bit (a fraction of a mm). So the spark was erratic. Bringing the gap back to 0.3mm (12 thou) it is working perfectly well again. When playing with the magneto, I saw that the spark when turning it slowly by hand was much stronger than from the coil ignition. I like the magneto and keep the coil in the car just in case.
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