[Blue 69]

Wiring up a test stand from scratch. How would i run power to the coil for ignition? I see some diagrams running straight 12V while others show a ballast resister???? BTW I'm running a points distributor.

 

[GTO44]

Points distributor will need a balast resistor as they dont run on 12v. They need 12v during cranking which is why certain starters or starter solenoids have an “I” post or terminal. This also goes to the coil + to provide 12v during cranking. As soon as cranking stops, 12v goes away and the coil is powered thru the ballast resistor wire.

Now you could do a Pertronix points conversion which uses the same points distributor but ditches the points with a magnetic pickup. Then you can run a straight 12v and have more powerful ignition spark.

 

[Blue 69]

Soooo at the time of cranking is power fed by both the wire from the solenoid and the resister wire?

 

[chaze]

I'm wondering how much arc damage to the points would occur if you ran 12 volts to the coil without a ballast resistor during engine stand tests. Seems to me it would be minimal.

 

[chaze]

Soooo at the time of cranking is power fed by both the wire from the solenoid and the resister wire?

Electron flow will follow a path of least resistance so my assumption is that DC current would only flow to the coil via the starter solenoid wire during cranking and revert to the resistor circuit once the cranking circuit is eliminated via the start (key) switch.

 

[GTO44]

Soooo at the time of cranking is power fed by both the wire from the solenoid and the resister wire?

Electron flow will follow a path of least resistance so my assumption is that DC current would only flow to the coil via the starter solenoid wire during cranking and revert to the resistor circuit once the cranking circuit is eliminated via the start (key) switch.

Its the same power source so its the same voltage (not additive).

For an easier example lets look at lets say an electric fan. Fan has a 14 gauge positive 12v source and a ground. Now if we run another 14 gauge wire from the same battery to electric fan it won’t have 24v (12v x 2)... it will still be 12v. But what we’ve done is effectively increased our gauge size and consequently allows for more current (amps) to pass to the fan. Two 14 gauge wires would be around a 10 guage wire.

So when the 12v gets applied by the starter solenoid it just overrides the 6volts from the resistor wire. When the cranking stops the voltage drops down to 6 volts.

 

[GTO44]

Soooo at the time of cranking is power fed by both the wire from the solenoid and the resister wire?

Its the same power source so its the same voltage (not additive).

For an easier example lets look at lets say an electric fan. Fan has a 14 gauge positive 12v source and a ground. Now if we run another 14 gauge wire from the same battery to electric fan it won’t have 24v (12v x 2)... it will still be 12v. But what we’ve done is effectively increased our gauge size and consequently allows for more current (amps) to pass to the fan. Two 14 gauge wires would be around a 10 guage wire.

So when the 12v gets applied by the starter solenoid it just overrides the 6volts from the resistor wire. When the cranking stops the voltage drops down to 6 volts.

 

[Dean]

Soooo at the time of cranking is power fed by both the wire from the solenoid and the resister wire?

Yes, the starter's R terminal (yellow bypass wire) feeds 12 volts to the coil when it is cranking the engine, bypassing the resister wire..

 

[71350SS]

I'm wondering how much arc damage to the points would occur if you ran 12 volts to the coil without a ballast resistor during engine stand tests. Seems to me it would be minimal.

In the 80's I had a 65 Chevy Impala and for some reason (I probably did it when I R&R'd the heater core from the AC plenum) the resistence wire lost continuity to the coil so it would start and stall immediately after releasing the key from start.Being the middle of the winter and too cold to fix it I ran a jumper wire from the battery to the coil positive for well over a month.After fixing the wire there was no additional wear and tear on the points when I checked them because everyone told me I would burn up the points wiring it like that straight to the battery. I noticed no running problems wiring it like that.

 

[Dean]

In the 80's I had a 65 Chevy Impala and for some reason (I probably did it when I R&R'd the heater core from the AC plenum) the resistence wire lost continuity to the coil so it would start and stall immediately after releasing the key from start.Being the middle of the winter and too cold to fix it I ran a jumper wire from the battery to the coil positive for well over a month.After fixing the wire there was no additional wear and tear on the points when I checked them because everyone told me I would burn up the points wiring it like that straight to the battery. I noticed no running problems wiring it like that.

Same thing on my nephew's 66 Impala before I ever knew about the resister wire.
His resister wire went bad and I ran a 12 volt wire from the ignition.
He never had any problem with the points and the car was still running fine when he traded it in over a year later.

 

[chaze]

Now if we run another 14 gauge wire from the same battery to electric fan it won’t have 24v (12v x 2)... it will still be 12v. But what we’ve done is effectively increased our gauge size and consequently allows for more current (amps) to pass to the fan. Two 14 gauge wires would be around a 10 guage wire.

EDIT: PLEASE DISREGARD THE CONTENTS OF THIS POST - See post #15

My electronic engineer brother sez...NOPE.

Current will only flow through the wire that offers least resistance - it will not flow through both simultaneously and therefore amperage capacity would not increase.

 

[GTO44]

My electronic engineer brother sez...NOPE.

Current will only flow through the wire that offers least resistance - it will not flow through both simultaneously and therefore amperage capacity would not increase.

Hmmm so all the pro motorsport wiring guys that use 2 to 3 12 gauge wires to pass a high load thru a bulk head connector have had it all wrong. Dang!! Thank goodness for your brother now everyone can be doing it right!

 

[Blue 69]

THANKS Guys for the help. So it sounds like running 12V straight to the coil would be fine for my intent( 20 min. run stand to break in the cam)

 

[Dean]

Hmmm so all the pro motorsport wiring guys that use 2 to 3 12 gauge wires to pass a high load thru a bulk head connector have had it all wrong. Dang!! Thank goodness for your brother now everyone can be doing it right!

But none of those wires is a resister wire.

 

[chaze]

Hmmm so all the pro motorsport wiring guys that use 2 to 3 12 gauge wires to pass a high load thru a bulk head connector have had it all wrong. Dang!! Thank goodness for your brother now everyone can be doing it right!

I contacted my brother and neither of us could recall the conversation criteria that led to the below quoted interpretation mentioned in a prior post:

"Current will only flow through the wire that offers least resistance - it will not flow through both simultaneously and therefore amperage capacity would not increase."

MY INTERPRETATION in the above quote IS INCORRECT.

Sorry for the erroneous post. GTO44 is correct and below is a link that confirms his conclusions.

Combined Wire Gayge Calculator

 

[71350SS]

THANKS Guys for the help. So it sounds like running 12V straight to the coil would be fine for my intent( 20 min. run stand to break in the cam)

That's what I would do I really doubt that will damage any points sets you're running plus the same ignition wire & switch can be used for your HEI's too.