63-67 ballast resistors

[Brian J.]

I have an NOS ballast resistor GM part #1957154 D1110 in the box. In the 66TIM&JG it doesn't say anything about a blue stripe across the top terminal. Can anyone clue me in if I have the correct balast resistor. It also says the originals have small notches on the attaching tab mine does not. Any help will be greatly apperciated.
I'm one of the young pups born in 65, you guys know everything, thanks for all your input.
Brian Juraska NCRS# 32829

[Mike M.]

Re: 63-67 ballast resistors

brian: the judging man. is correct. if your NORS BR doesn't have a tab on the attaching bracket, the judges will have a problem. locate an orig BR in junk yard off early to mid 60's GM cars(olds, caddy chevy etc) to see what the config of an orig br bracket is supposed to look like, then carefully grind a tab into the nos bracket. Its fun to fool the judges . mike

[Duke W.]

Re: 63-67 ballast resistors

What you have is an example of the "common" 1.8 ohm ballast that was used on most Chevrolet and Corvette engines in the '63 - '67 era and beyond until the ballast was incorporated into the wiring harness on C3s.

Very early 1963 Corvette engines (all four power ratings) used the 1931385 ballast, which is only 0.3 ohm. The lower resistance provided higher primary current for more ignition energy, but it was tough on points and there was a relatively high incidence of customer complaints due to burned points. As a result, Chevrolet modified the coil/ballast utilization. For the remainder of '63 and '64, SHP/FI engines continued with the 091/385 coil/ballast combination, but 250 and 300 HP engines were switched to the higher resistance 754 ballast along with the "087" coil. You will find the evidence of this change in the engineering change record of Sect. 7 Sheet C7.00 and the L-76 and L-84 sections of the '63 AIM. Also, Chevrolet wrote a TSB on the situation documenting the production changes and field fix for burned points, which was to install the higher resistance ballast for winter operation. I believe that beginning in '65, all engines, including SHP/FI used the 784 ballast along with the new "202" coil.

At the '02 National Convention I submitted a letter with backup documentation to the '63 Team Leader as the current '63 JG is incorrect on coil utilization, but never received a response or feedback.

Both the 385 and 754 resistors have the same ceramic body and bracket and can only be identified by measuring their resistance. Also, over the years the configuration of the ceramic base and/or bracket underwent some minor changes (I think Jack Humphrey has posted the details). There is some controversy as to whether the "blue stripe" (784) and "black dot" (385) were visible on plant installed resistors. My feeling based on the available evidence is that they were not - only the service parts were so maked with this informal identification.

Duke

[frank mccracken]

Re: 63-67 ballast resistors

So with 12v going into the ballast resistor, what voltage should becoming out of the ballast resistor to the coil?

[Duke W.]

Re: 63-67 ballast resistors

Depends on the primary resistance of the 202 coil. The spec should be in any service manual for any year that the 202 coil was used.

Two resistors in series form a voltage divider circuit with the drop across each resistor proportional to its share of the total resistance, so if R1 and R2 are the ballast and coil primary resistances respectively, the voltage drop across the ballast is V x R1/(R1+R2) and the drop across the coil is V x R2/(R1+R2).

In the case of an operating engine "V" is system voltage which is usually about 14 volts depending on temperatures and regulator settings, so you can compute the voltage drop and then check with an ohmmeter, and you should probably find that the voltage drop across the coil is in the range of 8-9 volts with the remaining drop across the ballast.

The resistance of the ballast varies with temperature and increases as it gets hotter. This helps limit current across the points to keep them from burning. A couple of years ago the late Dale Pearman went into long winded explanations of how the ballast was really an "analog computer". He argument had plenty of merit, and was rather quaint, but I don't think most bought into it.

Duke

[frank mccracken]

Re: 63-67 ballast resistors

Thanks Duke! The reason I ask is I have an old tractor converted to 12v. I installed a ballast resistor to the coil to preserve the points but on checking I discovered that there was allmost no voltage drop to the coil. Approx 2 ohms resistance across the resistor. But if the resistance increases as it gets hotter, that should work fine but it creates a question. If the resistance starts out low and increases, it seems to me that there isn't a need for a start circut with the full 12V?

[Duke W.]

Re: 63-67 ballast resistors

I'm not that familiar with 6V systems, but I assume 6V coils have lower primary resistance than typical 12V coils. Installing a ballast in conjuction with the conversion to 12V was a good idea, but you should also buy a 12V coil. Any generic 12V coil with an approximately 1.8 ohm ballast should do.

During cranking battery voltage drops off to 9-10V, so that's why the starting circuit bypasses the ballast. This arrangement ensures at least as much current as when it is operating in normal mode with the ballast in the circuit to assure plenty of ignition energy during cranking for a fast start.

Duke

[frank mccracken]

Re: 63-67 ballast resistors

That makes sense, Thanks again Duke.

[Joe C.]

Hey Mike....Naughty, Naughty.......

....but I done the same thing, heh, heh. Somebody else told me to slop up the attaching area with "dum-dum" to hide the tab. But I didn't do that. I haven't found anyone yet, with the temerity to trash my "tab", because it's a real good lookin "tab".

Joe

[Jack H.]

Both blue stripe and black dot....

are called out on the respective ballast resistor part drawings and the Engineering Change Revision history of both documents does NOT indicate 'added' or 'deleted' episodes.

So, where do you think it'd be more important to have the color code distinguishing marks used--on factory parts that were shipped in bulk and 'binned' or on service parts that were individually boxed and labeled? I doubt we'll get agreement on this one....

But, remember both versions of the ballast WERE used in the same factory setting (St. Louis made trucks and pass cars with low performance ignition systems too) AND there was a period (e.g. '63-64) when the same parts were intermixed on the Corvette assy line (low performance ballast + coil for hyd lifter engines & high performance ballast + coil for solid lifter engines).

I can't tell you what's 'right' but I have my hunch based on the above.... Plus, the identifying marks were simple ink--easy to wear/fade away over time.

[Zachary K.]

Re: Hey Mike....Naughty, Naughty.......

Hi Joe, or anyone else with a digital camera. Can you post a picture of this tab and the approx. dimensions. I've been hit quite a few times during judging for this. I've searched junkyards in my area for these and haven't been able to find any as the old bones have been picked over pretty good by the vultures. I have an over the counter NOS GM resistor with blue stripe, and a spare but both are the same w/o tab. Thanks for the help.