Technical Wiring Help

[luigirox]

So I am starting to put my car back together
Fiat 500r 1975. I noticed that it was setup for positive ground and ignition coil was wired with the positive end to the chassis. I think it has dynomo and not alternator. It has a regulator on the firewall.

Questions
Why would it be setup for positive ground?
If I switch it to negative ground do I have to change something with the dynomo?
I am just good with switching the coil over to negative to the chassis.
I attached some pictures

 

[bugsymike]

So I am starting to put my car back together
Fiat 500r 1975. I noticed that it was setup for positive ground and ignition coil was wired with the positive end to the chassis. I think it has dynomo and not alternator. It has a regulator on the firewall.

Questions
Why would it be setup for positive ground?
If I switch it to negative ground do I have to change something with the dynomo?
I am just good with switching the coil over to negative to the chassis.
I attached some pictures

Others may have more advice, but personally I am of the "if it ain't broke don't fix it brigade" regarding this. Basically if you want to run an alternator which has benefits in higher better regulated output etc. then you have to run Negative earth as that is the way they are designed.
But dynamo systems are generally Positive earth, although I believe I read somewhere that they can be set to run Negative earth by flashing the field winding terminal, but read up about it first and like the coil and possibly the radio and other things you will need to change that, so don't just dive in!

 

[luigirox]

Im am going to wire it as it was with postive ground. I just find it strange it was this way.

One question is there a way to test lights horn etc without the motor in the car?

 

[bugsymike]

Im am going to wire it as it was with postive ground. I just find it strange it was this way.

One question is there a way to test lights horn etc without the motor in the car?

That is what I would do.
Nothing strange about positive earth, probably used for over 80 years until alternators came along, when I started as an apprentice in 1969 every vehicle had a dynamo, gradually in late 70s started to see cars with alternators.
As long as no wiring left hanging to short out from working on engine , then no reason not to be able to test horn and lights etc.
As a precaution in case you miss something only drop the terminals on the battery loose, don't bolt on solid then you can whip them off if needed.