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Negative Earth Conversion ?

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DavidThorn

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I know this has been discussed before in this forum but I cannot now find anything about Negative earth Conversion`s
The car is a late BJ8 and as a winter project I am considering such a conversion - so that I can use a modern radio and more importantly Sat Nav.
What are the pros and cons ? I read somewhere that corrosion is inhibited by Positive earth - can that be true? Would a change now after 40 years possibly make corrosion easier?
Also what are the physical steps? I am aware of the need for a fuel pump - I have a modern dual polarity one so that would not be a problem but can the rev counter be adapted and if so how? Finally concerning the wire from the coil to the cut off in the boot (trunk) is that retained ? If not will the cut off switch work with Negative earth.
 
Hi David,
Take a look here for the conversion steps including changing the loop behind the rev counter. The cut-out switch in the trunk wouldn't be affected by the change.
 
I forgot to mention. You didn't say whether or not you'd switch to an alternator. The late BJ8s had a max 30 amp generator. I'm not sure how big a radio you want to run. :blush:
 
David -

If you have the fuel pump sorted already, the only thing to worry about is reversing polarity on the Tach. You can do it yourself if a later tach. If you have an early tach it's best dealt with by either Margaret Lucas or Nisonger.

Note that there is no difference with positive or negative ground, and of the 4 British cars I own, I've converted three to negative ground. I only keep the BN1 positive ground as I have no need for a radio or any sort of electrical doo dads in that car. There are no cons to conversion - it will make no difference on corrosion.

Cut off switch will work just fine either way.

One last note - if you have a Pertronix EI on your distributor, you will have to change that unit and swap the leads on your coil. If you just have points, you can leave them as is.

Alan
 
Thanks for the info and the link.

It all looks pretty straightforward. I do not have electronic ignition just points.

I was only intending to use an old FM radio of the period - nothing fancy -I dod not intend to change to an Alternator.

One point in the Link it talks of swapping over the wires to the Coil but after starting the engine - shouldnt it be before,or will it run either way around?
 
DavidThorn said:
One point in the Link it talks of swapping over the wires to the Coil but after starting the engine - shouldnt it be before,or will it run either way around?
Click to expand...
Hi David,
It will run either way and you probably won't notice a difference driving. From what I understand, the plugs last longer when you switch the leads. Meaning you keep the relative polarity the same.
 
Hi David,

One of the " pro's " of doing the negative ground conversion is that if you should ever need more electrical power in the future, you will have many choices of alternators as most/all of them are for negative ground systems.
1/2 of the work will have already been completed and tested for an alternator upgrade.
Another " pro " is that you can easily install the negative ground LEDs from Roger's LED conversion of your dash light bulbs. This allows you to clearly see all of the gauges after dark and you can actually see your green turn signal arrows on your dash as well as the high beam indicator IN BRIGHT SUNLIGHT !
Ed
 
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