Did the 56 Buick use a 12V positive ground electrical system

[56 Buick]

Hi

 

I am after a bit of help here.  Now i always assumed the mid fifties GM cars all had negative ground systems but I am looking at the distributor and coil and the points wire runs from the distributor to the positive terminal of the coil and the negative terminal of the coil is connected to the ballast resistor. My understanding is that this makes it a positive ground system?

 

Do the 56 Buicks use a positive ground system or has someone wired up the coil incorrectly?

 

Thanks

 

Drew

[56 Buick]

But having looked at the battery terminals, the negative terminal is grounded onto the engine block - so that means it is a negative ground system.  That being the case then it seems to me that the wiring to the coil is not correct.  The points wire from the distributor should run to the negative terminal of the coil and not the positive terminal of the coil.  Having said that, I am not sure what effect if any occurs when the coil is wired up on a different polarity.  Anyone have any advice?  Thanks

[JohnD1956]

It should be 12 volt negative ground. And the wire from the ballast resistor should go to the positive terminal on the coil. Negative terminal of the coil goes to the distributor. But whatever damage could have been done to the coil is a question I cannot answer. 

[old-tank]

Look at the wiring diagram in your service manual.

[Frank DuVal]

No damage to coil, it  does not care. 

 

BUT! The spark plugs care. Care about polarity I mean. 

 

1. electrons are emitted by the negative terminal of a source. The electrons travel to the positive terminal of the source.

 

2. Sparks are electrons

 

3. Easier for an electron to travel from a point source to a large "positive" electrode (plate in electron tubes are an example).

 

So, therefore,  the spark plug wants the center electrode negative with respect to the outer shell/large L shaped electrode.

 

The way to get an ignition coil to make the center high tension terminal (the one that goes to the center terminal of the distributor and the spark plugs) negative is to hook the + and - small terminals of the coil properly.

 

On a negative ground car, this means the - terminal of the coil goes to the points.

 

On a positive ground car, this means the + terminal of the coil goes to the points.

 

'Lectricity lesson over.

 

Oh another question? What is the effect of wrong spark plug polarity?  Poor higher speed performance. 

 

BTW, look in an old general shop manual and you will see the pencil test for correct spark plug polarity. 

 

AFAIK, only Packard used the 12 volt POSITIVE ground system in American car production, and just for one year. Foreign, that's another story, Lucas seemed to like it....?

[56 Buick]

Many thanks. It appears that for whatever reason someone has wired the coil up the wrong way.  I will set it correctly.

[Joseph P. Indusi]

As described above, coil polarity is very important.   A friend has a beautifully restored 1940 Ford convertible that had driveability problems under load.   On these cars they often replaced the original coil including the mounting position.  This is a positive ground 6 volt system.  I checked the coil wiring and found that it was incorrect.   Once we changed the wiring to the correct polarity the problem disappeared.  

Joe, BCA 33493

[37_Roadmaster_C]

The polarity of the coil may or may not have a real effect on performance of the engine.  I am not a expert and do not dispute the findings of those above that have had real world findings.  I only want to point out that sparkplug  polarity is ignored in several current or slightly older designs. Look at the GM coilpack operation as used in many V6 and V8 models.  That design has sparkplugs connected to both ends of the coil that fire at the same time. With this design, one plug is firing center to ring while the other one is firing ring to center. These engines seem to run very well on all cylinders, not just half of them.  Just something to think about........

[1956322]

In my experience engines with what is called a wasted spark ignition system do seem to run a little off.. But maybe that has more to do with the v6 reality.. Also pretty early on they discovered abnormal wear on the plugs so they switched to double platinum to address that issue.

[Frank DuVal]

Actually, it is the higher voltage of the new ignition systems that overcame the spark going the wrong way. Old points/ coil system still needs to observe polarity of the spark plug.

 

From Motor magazine back in 1999:

 

 One plug fires with the traditional forward polarity of an ignition system: negative (2) to positive (1) The other plug fires with opposite polarity: positive (1) to negative (2) Thus, one plug always fires with what has always been called "reversed polarity." The voltage capacity of a DIS coil is high enough, however, to ensure that the available voltage is always high enough to fire the plug with reversed polarity when it's on the compression stroke.

[37_Roadmaster_C]

Excelent info...  Thanks