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+--- Thread: Distributor mystery (/showthread.php?tid=7609)
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Distributor mystery - Nick Mayne - 10-06-2022
Having just received a new strobe I started to set up the timing on my 1932 AVG (RN) van. I realised the advance was not working at all so took my Bosch distributor apart only to find that the balance weights were very neatly welded together and I attach a close up. How can this possibly happen? I have several fuses in my wiring including a master fuse but none are blown.
The history is that I originally had electronic ignition in the unit but changed it to normal points. I just found that the rotor arm lacks continuity but maybe there is a condenser or similar buried there?
Also I have just had the dynamo armature and filed coils rewound for 12 volts
I was thinking of buying a new distributor from Powerspark but am worried this could happen again. I do not know when it happened which is a problem.
Erudite advice welcome!
RE: Distributor mystery - John Cornforth - 10-06-2022
Hi Nick
I can only think that someone in the past has welded up the weights so as to use it on a manually adjusted system. Nothing to do with the car's electrics.
Some rotor arms have a suppressor resistor between centre and tip. This component is sometimes encased in the insulation or under "potting compound". They should read roughly 5000 ohms. If it shows open circuit, throw it away and replace it with a good quality new one.
RE: Distributor mystery - Adrian Payne - 10-06-2022
Hello Nick
This is not due to an electrical short. Someone has arc welded the weights together for some reason.
Adrian.
RE: Distributor mystery - Charles Levien - 11-06-2022
(10-06-2022, 08:10 PM)Nick Mayne Wrote: Having just received a new strobe I started to set up the timing on my 1932 AVG (RN) van. I realised the advance was not working at all so took my Bosch distributor apart only to find that the balance weights were very neatly welded together and I attach a close up. How can this possibly happen? I have several fuses in my wiring including a master fuse but none are blown.
The history is that I originally had electronic ignition in the unit but changed it to normal points. I just found that the rotor arm lacks continuity but maybe there is a condenser or similar buried there?
Also I have just had the dynamo armature and filed coils rewound for 12 volts
I was thinking of buying a new distributor from Powerspark but am worried this could happen again. I do not know when it happened which is a problem.
Erudite advice welcome!
Hi Nick, I’m using a Lucas ( ex Mini) distributor with electronic ignition supplied quite a few years ago. I think the system is called Magnetronic, with a black plastic disc that holds four magnets — I was in touch with Pigsty at the time as they were making a four branch exhaust manifold for me. I got talking to Tim Myall about electronic ignition and he advised welding the weights together, which he subsequently did for me.
This has certainly worked very well on my special — brisk acceleration and no loss of flexibility. With light throttle it will happily pull away from 20mph in top gear. Of course 15ins rear wheels helps.
I subsequently fitted Powerspark to my Opal using the original DK4A with 6v positive earth. The Bob weights on this car are still ‘’working’’. The Opal runs beautifully.
I hope my experience is helpful — in your case you could apply that old adage, suck it and see.
Charles.
RE: Distributor mystery - Nick Mayne - 11-06-2022
Thank you all for the information. I bought the Bosch distributor advertised as new on Ebay and have no other detailed records....a mistake maybe as I suppose it could have been welded. I think I would have disassembled it as I had to have some machining done on the body (known problem) but perhaps did not look at the bobweights. Also Pigsty looked at the mixture (made a special needle) and timing for me and I suppose they could have welded the weights without me knowing however I did not have a rod from the steering column. I might try to cut open the welds and clean up the weights and suck it and see! I had already added a small stop to limit the advance to about 3 degrees which I was told was about right as the Bosch otherwise had a much larger advance.
My engine is tuned in so far as it has a medium machined camshaft and followers and oil filter and machined oil pump from Pigsty and they also sold me a Nippy manifold. The engine also had oversize inlet high spec valves, double valve springs, an inlet manifold from John Barlow and a high compression head. John Barlow also supplied his new crankshaft, NC machined con rods and special pistons with floating gudgeon pins. I only aimed for a bit more power but got rather carried away as it is only a van hard to keep in a straight line and hard to stop!! The fuel consumption was very high and that was why I took it to Pigsty. They pointed out that the engine did not fit regular specs so they modified the SU needle in a lathe using emery paper! I find it hard to believe they welded those weights but will not ask now as it was a long time ago. Will keep you posted.
RE: Distributor mystery - Nick Mayne - 11-06-2022
Got weights separated and put all together. Engine runs but advance not smooth with sudden extreme advance so I need a new distributor. The Powerspark one seems to have the electronic option and using that I would have to abandon my nicely made copper wire HT leads as the small print says they would not be suitable so why is that?
Could someone increase my knowledge and tell me why there is a high value resistor in the rotor arm?
RE: Distributor mystery - Charles Levien - 12-06-2022
Hello Nick,
I do hope you get it all sorted out but I’m left with an image of you hurtling along in your 60mph van, with no brakes.
Is this a good idea?
RE: Distributor mystery - Terrytuned - 12-06-2022
Copy of Bosch rotor arm Article. Terry.
RE: Distributor mystery - Alex Myall - 28-06-2022
At Pigsty, we have done extensive dyno testing of many types of A7 engines and have found that the engine does not need an advance curve in the distributor. The dyno data shows that with fixed timing if the ignition is retarded slightly the peak power goes up very slightly high in the rpm range but the bottom end loses power. However, this does make the engine kick back when hand-cranked.
RE: Distributor mystery - Hedd_Jones - 28-06-2022
That pretty follows the advice as I remember it in the handbook for the manual set up.
Retard to start, when running move the lever to the fully advanced position.
Which is what I did on my chummy with a manual advance/retard on the dizzy.