How to select the right points for single point distributor
#1
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How to select the right points for single point distributor
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
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
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ttt
#4
Safety Car
thanks Duke for the info .......
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ttt... in case anyone missed it.
#7
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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
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
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Dan
#10
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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
Dan
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
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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
Last edited by dplotkin; 12-18-2021 at 11:47 AM.
#12
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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
#13
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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
Dan
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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
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
Dan
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