Coil help ?

I have a Flamethrower coil in my '52 F1 and really like it. I installed it first and later (several weeks) put in the Pertronix igniter kit to replace points in distributor. Just the coil was a big improvement and the Pertronix kit really finished the job!!
 
ctaulbert said:
Jim - I'm running a 3-4 ohm internally resisted coil on my stock distributor V8 (in an effort to not have to mount a ballast resistor somewhere on the car). Based off your comment, you would suggest replacing it with a 1.5 ohm coil with a 1.5ohm resister?

Just looking to get the best performance out of what I have......

For what it's worth, I do have one of your electronic crab setups on another car!
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I don't like mounting a ballast resistor also, so I use a resistance wire to the coil. I swiped it out of an old 60's Ford wiring harness.
 
flatjack9 said:
I don't like mounting a ballast resistor also, so I use a resistance wire to the coil. I swiped it out of an old 60's Ford wiring harness.
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Thats good ! NAPA has a section in their catalogs for these resistance wires .
In actuality the oems have used these resistance primary ( called a loom resistor) for a long time.
Plus the wire from the coil to the distributor is considered a resistance cable as well. It is a finely stranded cable and eats up the final voltage before the points..
If you do the math on a 1.5 coil and a 1.5 resistor and 12 volt battery.
Total resistance is 3 ohms divided into 12 volts= 4 amps of current draw.
Voltage drop is amps times the draw which would be 3x4= 12 volts. Pretty good until the engine starts and we charge the battery at 14 volts.
Then the coil would drop 4x1.5 or 6 volts and the resistor would do the same leaving 2 volts extra. The heat and additional primary wire from the coil will handle this extra 2 volt shot leaving a very small amount at the contact points. Maybe a couple tenths etc......

Then the hot rodder in us replaces this distributor lead with 14 gauge and all that final protection is gone....:eek::confused:
 
Bubba, what method would I use to test an original 1940 Ford coil with the stock helmet distributor? Have you already covered this subject and I don't understand it enough to see it?
 
L78CHEVELLE said:
Bubba, what method would I use to test an original 1940 Ford coil with the stock helmet distributor? Have you already covered this subject and I don't understand it enough to see it?
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No i would need to drag one down and hook it up. It would have a primary ( low ohm) side as well as a secondary side as well.
I will post up a couple pictures etc.......
 
BUBBAS IGNITION said:
The GM HEI module needs a .5 ohm coil to activate the current limiting and coil controls designed in the module.
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The two coils I have on hand for HEI both measure 0.9 ohms. Would there be any seat of the pants advantage to going to a 0.5 ohm coil?

And who makes a "genuine" quality GM module now?
 
Richard in Florida said:
The two coils I have on hand for HEI both measure 0.9 ohms. Would there be any seat of the pants advantage to going to a 0.5 ohm coil?

And who makes a "genuine" quality GM module now?
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I would have to use a amp probe and a scope to see the difference , however there would be a pretty good sized difference.
Using wattage with 12 volts the .5 coil would be 288 watts and the .9 would be 156 watts.
The only visable difference on a lab scope would be the rise time.
The rise time of a coil ( as well as current) is controlled by one of two methods.
1=Time =The coil and engine ( number of cylinders and resistance) would control the rise time ( ramp) build up of the coil by design and it would just ramp and fire in a givin amount of time. Many of todays vehicles work like this.

2=Current Limiting ( GM HEI) would control the current using a peak and hold circuit. The current would peak ( in this case in 3.6 mili seconds) and hold ( at 5.5 amps) until the firing point.

I think if you have a current limiting module its better to push the circuit as designed , in this case using the proper coil .

It will work either way .
My sons slant six hot rod uses a GM HEI module mounted on the fender triggered by the factory chrysler distributor and a standard old chrysler coil ( more than likely a 1.5 ohm unit) and works very well and has for years.
In his case we were at the Goodguys event in Columbus Ohio a few years ago and his module ( factory chrysler) died on our way in one morning.
I had a booth in the swap meet and bought a old GM Hei for $10 , removed the module and grounded it with a existing screw in the fenderwell wired it up and its been there for a few years , starts very well and runs great !!!!!:eek::D
I think he finally cleaned up the wiring job after he got back to Indianapolis....

Beats me on the best HEI modules today, i would just buy from someone that would warranty them when they fail.
In my mind the best you could ever get would be a orginal GM hei core from a swap meet or something. If marked delco/GM it would have all the circuits....

Maybe we could get the internet guys to round some up and send them to us for testing . I bought two heis ( really nasty ones) from my trash person this week, both had good GM modules in them.....
 
A Coil by Any Other Name...

BUBBAS IGNITION said:
I think if you have a current limiting module its better to push the circuit as designed , in this case using the proper coil.
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Lemme see... I think you just said if I have a gen-yoo-ine Delco GM module, the proper coil (0.5 ohms) would get the most out of it... but I probably wouldn't feel it.

Is that about it?
 
BUBBAS IGNITION said:
Plus the wire from the coil to the distributor is considered a resistance cable as well. It is a finely stranded cable and eats up the final voltage before the points.
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Yup, I've heard that before, but those wires on distributors I've salvaged are always charred or missing. Where does a fella get 'hold of some of that wire?
 
I must be spoilt,on my stock 33 and 34 with the 6v setup ,repaired coil runs great,starts on half a turn on the starter.
Lawrie
 
I've got a bunch of coils here from several models and they range from 1.4 to 1.7, have no idea where they come from. I also have a 3.2 with an internal resistor. Now my meter is a cheap one and the accuracy may be questionable
 
Bubba, hope you don't mind me asking because some where you probably covered this .
on my original 30 coupe what should my coil read primary and secondary.
 
Just a word of caution ... when measuring the coil primary resistance, be sure to make a measurement of your test leads shorted together at the probes. Because the resistances are so low, you can easily have a half ohm or more error in the meter and test leads. So measure with the leads shorted ... say you measure 0.5 ohm. Then measure the coil. If you get 1.8 ohm, then the real reading of the coil primary is 1.8-0.5 = 1.3 ohms.

Also the temperature is a very important parameter to make sure you are getting valid readings. Copper wire has a positive temperature coefficient of about .3% per degree C. So a coil that has been operating at say 80C inside the car will actually read about 18% high at that temp relative to room temp ( 0.2 ohms or so).
 
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