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Hey Guys more stuff again,

Would anybody know the Resist Value of the ballast resistors on the ss1 1972
And also the point setting the book has a dwell angle of 26* to 28* but thats after the car is running right ? I need to get in the ballpark somewhere with my feeler guage first do you agree?

I have read somewhere that the rolls has a coil of 9V and must use a ballast resistors why can't we just use a 12V coil ?

Thanks again
Glenn
 

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Glenn,

All of your questions will likely be answered in by looking in the Workshop Manual and Illustrated Spare Parts Manual (along with a treasure trove of other documents) available at the Rolls-Royce Owners' Club of Australia Technical Library - SY Series Section.

Based on the designation in the Spare Parts Manual I'd have to believe that the coil is definitely a 12V and had been since the start, but I could be wrong.

So much depends on your specific chassis number and when, precisely, your car was made. Though sometimes upgrades took place at model year changes, there were many that were introduced at "in between" times.
 

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Speaking of ballast resistors:

I suspect that my 1975 Shadow with electronic ignition still has its original ballast resistor. What is the realistic life span of the ballast resistor? Should I have a replacement on hand just in case; or is it reasonable to leave well enough alone until there is a malfunction? Thank you!
 

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Hey Guys more stuff again,

Would anybody know the Resist Value of the ballast resistors on the ss1 1972
And also the point setting the book has a dwell angle of 26* to 28* but thats after the car is running right ? I need to get in the ballpark somewhere with my feeler guage first do you agree?

I have read somewhere that the rolls has a coil of 9V and must use a ballast resistors why can't we just use a 12V coil ?

Thanks again
Glenn
As a general rule, on a non electronic ignition system, the resistance of the ballast should match the resistance of the coil primary winding. Remove all low voltage connections onto the coil and use an Ohmmeter to measure the resistance across the terminal. My guess is that it will be 1.5 Ohms.

I've never come across a 9v coil and usually if you are reading this at the coil + terminal it's an indication that a 12v coil with a 3 Ohm resistance has been fitted instead of a 6v 1.5 Ohm item. It'll work but at far lower efficiency especially when the engine has eight cylinders

Mismatched coils were once quite common on 70's British cars as Lucas 12v coils were marked 12v wheras 6v (operating voltage) coils used on ballasted 12v systems were also marked 12v.

All contact breaker point systems draw about 4 Amps of current. Any less and the ignition coil will be inefficient, any more and the contact breaker points will burn prematurely which, once again, causes the coil efficiency to drop off.
 

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Speaking of ballast resistors:

I suspect that my 1975 Shadow with electronic ignition still has its original ballast resistor. What is the realistic life span of the ballast resistor? Should I have a replacement on hand just in case; or is it reasonable to leave well enough alone until there is a malfunction? Thank you!
Do you have the single resistor that's in a ceramic holder or the resistor block that looks like its enclosed in an aluminum envelope (and that has 3 male slide terminals at each end)?

Regardless of which you have, the consensus when I was asking about these is that they're generally very long-lived, though they have been known to fail on rare occasion.

The best explanation I've found for the ballast resistor block is on the page dedicated to same on the reopusignition.com website. The problem is that he has no data on the Lucas 9BR 47247A resistor block internals (and I've written directly to see if he did, but these had not been put up on his website). It would be great if we were to have this data.

I've attached a photo of the ballast resistor block from one of my two-series cars and a diagram I drew showing where the output wiring from the block goes.
 

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Thanks, Brian! Mine is the ceramic version; which I hope is the more long-lived of the two.
Having a spare on hand would not do me much good anyway because I can barely see the one in my car, let alone actually access it for replacement. This would be a job for my technician. Oh well . . .
 
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