63 Ignition Coil and Ballast Resistor and primary current goals

[Frederick W.]

I am looking to correct my ignition set up. My May-build 1963 327/300 has an old Delco coil that is not original and a newer ballast resistor, also not original. The coil primary resistance measures about 2.7 Ohms and the ballast resistor about 3 Ohms.

My understanding is that the correct coil for my application is the Delco-Remy 1115087 "087" coil with a 1.8 Ohm Ballast Resistor (this set up began on or about 2-12-63, vs. the earlier 091 coil/0.3 Ohm BR setup). I have not found information on this forum regarding the primary resistance of the 087 coil, or the desired primary current.
I did find in another source (Bill Carroll's "Chevrolet V-8 Performance Guide 1955-1971) that states that the primary resistance of the 087 coil should be 1.28-1.42 Ohms. Using 1.35 Ohms as the average of these values, and adding the 1.8 Ohm resistance of the correct ballast resistor would give 3.15 Ohms. This would translate into a primary current of 12/3.15=3.8 amps.

I have read many sources referring to approximately 4 amps as the ideal primary current to presumably create enough spark energy without burning the breaker points too quickly.

My set up with almost 6 ohms total resistance would net only 2 amps primary current. Yet I notice no issues with how the car runs with this set up.

Questions:

1. In selecting matching Coils and Ballast Resistors, what is the relevant issue? Is it the primary current? If so is about 4 amps ideal?
2. What noticeable deterioration in performance or function would I expect with my 6 Ohm total resistance set up?
3. Does anyone know if the GM Reproduction Parts 087 Coil has the correct +/- 1.35 Ohm primary resistance?
4. Is the Repro 087 "correct" in form/function and judging?
5. Is their a correct reproduction 1.8 Ohm Ballast Resistor?

Thanks for any input,
Fred

[Duke W.]

Re: 63 Ignition Coil and Ballast Resistor and primary current goals

Actual operating voltage is closer to 14, so primary current is a little higher than you calculated at 12V.

Four amps, steady state, is considered the limit to avoid point burning, and the higher the primary current, the higher the ignition energy, so any design is a tradeoff.

As long as your existing setup operates properl , which means quick starting and no misfiring, then it's good to go other than the originality factor.

There have been many discussions in the past about ballast resistors, both the 0.3 and 1.8 ohm versions mainly focusing on small physical differences over the years.

Nowadays there basically is only one SMP-manufactured coil and ballast available in various "brands" to replace all single point applications, but I don't have the specs.

Duke

[John D.]

Re: 63 Ignition Coil and Ballast Resistor and primary current goals

Fred Often I see NOS '087 coils for sale on Ebay. That would be my first choice for your May 63 300HP car instead of a repro.
I think the ballast resistor for that coil is a D1110 instead of a D1111. If not others can correct me.
The correct ballast resistor for judging is very hard to find. John