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Positive or Neg ground, should I switch?

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AH.MKII.Restomod said:
Can you make the alternator switch and remain pos earth?
Click to expand...
I think alternators came out after all cars went to negative ground. There might be some positive ground alternators, but they would be hard to come by and, thus expensive. Your typical alternator requires negative ground.
 
AH.MKII.Restomod said:
Can you make the alternator switch and remain pos earth?
Click to expand...

Anything is possible depending on how determined you are but it is much easier to swap the battery over. An externally regulated alternator has only the diode block earthed so it shouldn't be too hard to isolate that with some careful machining and addition of an insulation washer. The regulator is usually ground referenced so that'd need isolating and a 0V reference taken to the reg.

I'm currently running EFI on a Longbridge engine with positive earth and have only had one problem- the USB-laptop plug touched the gear stick and fizzed a circuit board track... There are always consequences when doing non-standard mods and for most ppl it is far easier to stick with known ways of doing things.

Andy.
 
According to Lucas a positive ground gives, less battery terminal issues, a 10% better spark efficiency and less wear on the rotor arm. The latter is due to the direction of the current. With a negative ground a small amount of metal is transferred from the rotor to the spark plug leads contacts each time it passes them. With positive ground the flow is the other way and therfore divided over 6 (or 4) contacts rather than just the one.
 
DerekJ said:
According to Lucas a positive ground gives, less battery terminal issues, a 10% better spark efficiency and less wear on the rotor arm. The latter is due to the direction of the current. With a negative ground a small amount of metal is transferred from the rotor to the spark plug leads contacts each time it passes them. With positive ground the flow is the other way and therfore divided over 6 (or 4) contacts rather than just the one.
Click to expand...

Where do Lucas say that about spark efficiency? I know they recommend a negative spark, where the spark jumps from the earth to the centre electrode on the spark plug, and hence from distributor terminal to rotor. However, that is not the same thing as negative or positive earth for the entire low-voltage system. Rather, that's a function of how the coil is wound, be it a coil intended for negative low-voltage earth or one intended for positive low-voltage earth. Modern coils are wound to give a positive earth spark - the plug electrode is negative relative to the block. This is called a negative spark. Confusing isn't it?
 
It's all electrickery to me

As I understand it, negative ground allows an alternator - more boys toys to spend your money on - giving more amps - equals nice shiny uprated lights in the dark.

Oh and something about corrosion, but can't remember what - :wall:

:cheers:

Bob
 
I did a search on the subject and came up with this interesting quote on a non-british car forum:

"



Someone told me that cars manufactured in the UK that have a positive
chassis electrical system, as opposed to negative, do not suffer from
rust. Is this true? Can anyone there confirm?

"

Discuss:emmersed:
 
Alternator was my first reason for to switch to NEGATIVE GROUND this make easy turn also to 123 Electronic Distributor- two big steps in reliability of my AH,
on my MG TD no modification is made- but in a night race, during a MG meeting, battery was completely drained by the head lamps absorption, my good, but poor
Dynamo haven't the right capacity to feed 100w continuous work
 
glemon said:
I did a search on the subject and came up with this interesting quote on a non-british car forum:

"



Someone told me that cars manufactured in the UK that have a positive
chassis electrical system, as opposed to negative, do not suffer from
rust. Is this true? Can anyone there confirm?

"

Discuss:emmersed:
Click to expand...

NO it is not true and if it were importing clean Healeys from the USA would not have occured.
 
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