63 FI Ballast resistor

[Michael G.]

At this point, it's about impossible to find an original 3.0 ohm ballast resistor for a 63 fuel car. Unfortunately, I have two of those cars and just one 3.0 ohm resistor. As I understand it, (from researching the earlier posts on this subject), the only reason I would need to use the 3.0 ohm resistor is to get maximum performance at 7000, or so, RPM. Since one of my fuelies now has a 327-350 hydraulic cam, it won't get anywhere near that, so I can (assuming I don't want to have the car judged) just use the common repro 1.8 ohm part instead, and get (supposedly) longer point life.

Is that a reasonable analysis?

Thanks,

[Timothy B.]

Re: 63 FI Ballast resistor

Mike, I think you got it right except I would be careful buying repro anything. Look for the more common 1.8 ohm ballast NOS, if you are patient one will come along. It will work fine with the 091 coil or a Napa ic-12 if that's what you have.

[Michael G.]

Re: 63 FI Ballast resistor

Thanks Tim, I have a repro in my stash of unused stuff. I'm wondering if there's a way to test it? I don't think that my multi-meter is accurate enough to measure such low resistance...

[Michael G.]

Re: 63 FI Ballast resistor

I tried it and it varied constantly, from about 0.8 to 1.8 ohms....

[Richard M.]

Re: 63 FI Ballast resistor

Mike, Yes you need a good meter.

Measure the meter lead error by shorting the 2 lead probes then record that error value. Measure the ballast then subtract the error value. Typically you will see lead errors of 0.1 to 0.2 ohms using a good quality meter.

Be aware that even GM NOS is not configured the same as the assembly line part.

Rich

[Duke W.]

Re: 63 FI Ballast resistor

At this point, it's about impossible to find an original 3.0 ohm ballast resistor for a 63 fuel car. Unfortunately, I have two of those cars and just one 3.0 ohm resistor.


Thanks,

The "low ohm" ballast resistor used up until 1963 on 12V Corvettes is 0.3 ohm, not 3.0. A running change replaced the 0.3 ohm with a 1.8 for the 250/300 HP engines along with the change from the ...091 to ...087 coil. SHP/FI engines continued to use the 0.3 ohm/091 coil through the end of 64 production. For 1965 all engines with single point distributors used the 1.8 ohm ballast with the ...202 coil.

Because of its lower resistance the 0.3 ohm ballast allowed higher primary current that created more spark energy, but it was tougher on points. They could actually burn and leave you stranded... happened once to my 340 HP SWC back in the mid sixties, and it was more of a problem in cold weather. GM wrote a TSB on the subject, and suggested swapping the 0.3 ohm ballast with a 1.8 during the winter months. I wonder how many people did that?

The physical configuration of GM service ballasts changed subtlety over the years, and there have been threads and Restorer articles on the subject over the years. So for judging you want one that conforms to the '63 production configuration, and AFAIK both the 0.3 and 1.8 look identical for any given production era, so the only way to distinguish is by measuring resistance. Some were IDed by the black dot (0.3) /blue strip (1.8), but IMO that only applied to service parts, not production line parts. I still have my original 0.3 ohm ballast, and it has no such marking, but I bought a replacement (purely for cosmetic reasons) in the seventies that does have a "black dot".

For normal driving, I think a generic 1.8 ohm ballast with just about any coil (for point type ignitions, not TI) will provide satisfactory performance as long as the distributor and secondary ignition components are in good working order and you use the 28-32 oz. breaker arm tension points on engines with redlines over 5500.

BTW, the P & A catalogs list the low ohm ballast as 0.03 ohm. That is an obvious mistake that was never corrected AFAIK.

Duke

[Michael G.]

Re: 63 FI Ballast resistor

My meter wanders all over the map: error varies from 0.1 to 0.6; resistor reads 0.6 to 1.4. I'll get another meter and try it.

Thanks Duke, I've gotta pay more attention to decimal points...Not too worried about 63 production configuration: this car has a repro frame, Tremek 5 speed, power rack and pinion, Vintage Air, a serpentine system, electric puller fan, Detroit Speed headlight motors, a silver interior (in a 63!), an in-tank fuel pump and so on. Not much judging in its future.

You might be interested in the fact that by removing the engine-mounted fuel pump and re-routing the fuel lines near the cowl, and adding the puller fan, I"m having zero, nada, no, problems with perc in the Rochester FI unit, even with the added heat from the A/C.

Mike

[Cecil L.]

Re: 63 FI Ballast resistor

Here's the TSB.

[Michael G.]

Re: 63 FI Ballast resistor

Thanks Cecil, very interesting stuff. Mr. Purcell (if he's still with us) probably never dreamed his letter would be dredged up in 2017...

[Brad V.]

Re: 63 FI Ballast resistor

SHP/FI engines continued to use the 0.3 ohm/091 coil through the end of 64 production.

Reading a different archived thread, it appears the 1963/1964 Judging and Spec guides are incorrect. They changed mid-year 1964 to 087 and 1.8 ohm for SHP.

Source: 1964 AIM | D301
1964 AIM, Section L76, Sheet 1, along the RH side of the page, under "The Following Parts Install the same as R.P.O. L75"
Revision Record Change Date: 1-13-64
Change 7: 115087 WAS 1115091
Change 8: 1957154 (1.8 ohm) WAS 1931385 (0.3 ohm)
---
Source: John Hinckley
https://www.forums.ncrs.org/showthre...ined-hopefully
You can follow the usage trail through the Assembly Manual and NPC's (Notice of Production Change) - it goes like this:
'56 - Early '63 all used the #1931385 (0.3 ohm) resistor; carbureted cars used the #1115091 coil.
TSB #DR-577 (2/27/63) described the February 4, 1963 production change at St. Louis to the new #1957154 (1.8 ohm) resistor on all 250hp and 300hp engines, " to eliminate point burning during cold-weather operation". The #1115091 coil continued on all points applications. It also noted that the Service parts would be identified with a black dot (for the old 0.3 ohm resistor) and with a blue stripe (for the new 1.8 ohm resistor).
The #1957154 (1.8 ohm) resistor continued to be released for 250hp and 300hp engines for 1964 start of production, with a new coil (#1115087).
NPC 307 and 328 released the #1957154 (1.8 ohm) resistor on 1/3/64 for L-76 (365hp) and L-84 (375hp) engines, replacing the #1931385 (0.3 ohm) resistor, along with the #1115087 coil, replacing the #1115091. For the rest of the '64 model year, all Corvettes with point ignition used the same resistor (#1957154) and the same coil (#1115087).
For '65 (and through 1967), all Corvettes with point ignition used the 1.8 ohm resistor, but the #1115087 coil was replaced by the #1115202 coil.
K-66 Transistor Ignition-equipped Corvettes didn't use a ballast resistor; the T.I.harness had a built-in length of special resistance wire instead.
In '68, the ballast resistor disappeared, and was replaced by a length of woven fabric-covered special resistance wire from the fuse block to the coil that served the same function until 1975, when the HEI ignition system was introduced, powered by a full 12-volt feed circuit.
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[Timothy B.]

Re: 63 FI Ballast resistor

I always wondered the difference between the 087 and 091 coils. My thoughts are it's got something to do with the windings and coil saturation time using points and high rpm's.