Positive VS Negitive ground

[mark171dodge]

The guy that rebuit my starter and generator sugested that i convert to negitive ground. Does anyone have information on if this is a good idea?

[Rusty O'Toole]

How and why did he suggest you do this? Certain parts are polarity sensitive, such as the radio and the ignition coil. Other parts like lights, starter, and heater motor don't care one way or the other.

You could do this by reversing the connections on the coil, polarising the generator, reversing the battery and replacing the vibrator in the radio but why bother?

[Don Coatney]

I know this is the truck forum but I suggest truck forum members hit the "Return to P15-D24.com" link on the above toolbar and read everything there. You may find an answer to your question.

[mechresto]

There is absolutely no benefit to swapping polarity, instead the inverse takes place, starter performance will diminish, it gets a little heady with the engineering calculations but boils down to this, DC current flows one way and the engineers at chryco, ford, chev, and 99% of the old car truck and tractor manufacturers took advantage of this. with pos ground there is more power available to the starter and other accessories. a few manufacturers even kept pos ground when the changeover to 12v took place.

There are several models of chryco vehicles that were equipped with 6v neg ground as standard, if memory serves it was ambulance and police. presumeably for compatability issues with the radio communications.

The regulator is one component that will also need to be changed as well if converting to neg grd.

In 40+ years of working on old vehicles i've only seen one come thru the shop with neg grd as standard.

Bryan

[Plymouthy Adams]

flash..

[jamesadams]

It would make installing modern equipment easier. My dad has a D-17 Allis Chalmers tractor 12 volt positive ground. It will start in any condition. I changed the points one time when the pads (both) were burnt completely off and the arm was blue,but it still started good. There must be something to this.

[Plymouthy Adams]

for that puppy to continue to start and run in theat contiion, the points breaker cam and point surface had to erode at about the same rate to continually keep the gap on the points to where they could close to saturate the coil and yet open to allow the coil's field to collapse..is this a working tractor or a static display unit..I could see it firing and running at idle but would imagine breadown of ignition under a real working load..somethings these things can amaze you..

[jamesadams]

for that puppy to continue to start and run in theat contiion, the points breaker cam and point surface had to erode at about the same rate to continually keep the gap on the points to where they could close to saturate the coil and yet open to allow the coil's field to collapse..is this a working tractor or a static display unit..I could see it firing and running at idle but would imagine breadown of ignition under a real working load..somethings these things can amaze you..

Thats why i was putting points in it,it would not pull a bushog. It started good, idled rough and had no power. I wished i had saved the old points,but that was 20 years ago.

[Rusty O'Toole]

I once did a tuneup on a 1967 slant six Dodge, that had a point gap of .003 that is, three thousandths of an inch.

I know because when I took the cap off the distributor I thought the points were completely closed so I checked with a feeler gauge.

The only symptoms were hard starting and a slight loss of power. That is why the owner wanted a tuneup.

[MBF]

The points gap makes a tremendous difference. I once had a guy bring me a Gravely with a Kohler 14 horse that he insisted needed a motor job. It had no power at all, and would barely rev. I did a compression check and it was right within specs. Went through the carb, and lastly the ignition system. Found the points were only opening about 4-5 thousandths. Replaced the points and set the gap-ran like a brand new engine. He was real happy with the bill and the turnaround time. Mike

[NiftyFifty]

If you have any plans to add accessories or upgrade gauges, lights etc it's a whole lot easier with a negative ground. I took the opportunity to re-wire my entire truck and convert to 12 volt also, another benefit when it's time for additions. My next add on will be an under the hood light...I seem to be doing a lot of night driving and if something happens it would be nice to see