SWCDuke

Download and read the attached pdf.

All referenced contact sets are manufactured by Standard Motor Products, but only NAPA part numbers are listed. Most can be cross referenced to other brands - same parts, just a different brand/part number on the container.

Duke

rene-paul

Very good info! Thank You!
Brgds,
Rene

SWCDuke

ttt

Mikado463

thanks Duke for the info .......

SWCDuke

ttt... in case anyone missed it.

narlee

Thanks Duke, nice to see actual data. Makes it easy to select the correct part for the job.

AZDoug

Dukes article brings up a question.

He references .3 ohm and 1.8 ohm ballasts...

If you are running a true modern 12V, non-ballast coil, will you burn points NOT having ballast in line with the coil?

Doug

VITIV Coupe

Thank you sir for the article, much appreciated.
Leo

dplotkin

12 volt breaker point ignition must have a ballast, either resistor or resistor wire. Primary current must be limited. The ballast rating varied with contact set application/engine/vehicle as as Duke reports GM changed this to deal with different ambient temps. No ballast = burned points fairly quickly depending upon type of points used.

Dan

AZDoug

Is that based on engineering analysis, or just repeating what you read/heard?

I was under the impression that the 1960s' ballast/coil system basically used a 6V coil, and the ballast was to reduce current to the coil due to the higher voltage. IIRC coil resistance was 1.8 ohms, plus 1.8 ohm ballast = ~3.5ohms total

A 12V coil that doesn't NEED a ballast with electronic breaker... why would you need ballast if you used contact points instead? I would assume (you know about assumptions), that a 12V coil has higher internal resistance, which would limit current thru the coil. Wouldn't a coil with higher resistance (say 3-4 ohms), not require a ballast?

Doug

dplotkin

Well Doug, we repeat what we read or hear when asked, that is called learning/teaching. Even the Duke himself didn't come down the chute with a-priori knowledge of breaker point ignitions. He learned from others too.
Ballasts were used primarily to deal with voltage drop weakening spark while cranking as most ignition systems, but not all, had some form of resistance in the primary circuit to throttle current. Some coils had the resistance built in, others external or resistance wire. 14.2 volt energy is enough to stress a coil and consume contact point face. Some amount of resistance in the primary circuit was almost always part of any ignition system whether 6 or 12 volts, sometimes it was just how the coils were wound.

My understanding as to Pertronix and other similar aftermarket systems is that the electronics requires a direct 12 volt feed, unballasted, but the coil needs primary current ballasted, regardless of the lack of points.

Dan

AZDoug

Thats if you use the factory coil. They make coils that are for 12V, direct line current use, with no ballast.

I suppose the VOM will tell whats up with each particular coil.

And yes, everyone learns something somehow, the difference is, is it school/engineering based learning, or shade tree mechanic "wisdom" (groove the crank main journals for better oiling for performance use) BS, that is just repeated with no thought given to if it is a correct answer, or not?

Believe it or not, some "performance " engine builder in PHX told me you have to groove the crank mains when you build a racing engine. he got pissy when I tried to explain you are cutting the bearing load capability by about 1/3-1/2 if you did that, so I took my business elsewhere.

Doug

2KREDVert

An "Old Wive's Tale" at best. Plenty of points distributors run just fine with no ballast resistor. And the points don't burn.

dplotkin

That would explain the millions upon millions of ballast resistors and resistor wires deployed across the majority of manufacturers.

Dan

dplotkin

I don't opine about that which I don't know Doug. I'm not an engineer. I own 9 antiques of various makes and learned what I know same as you. I read and I abide by those with proven wisdom. I come to my conclusions after seeing a variety of opinion. The views of career mechanics tend to carry more weight and value in my view, less so the hobby types you mention.

Dan

GTOguy

That's because they run a resistor wire as Dan stated, (like my Pontiacs).

dplotkin

And there you have it...Jeff (GTOguy) is a career mechanic.

Dan