After reading a previous post about ignition voltage to the coil and ballast resistor I thought I would do a little checking on my own. First of all this car, a '64 L84 is running fine. It does not have the original Delco coil however. Don't think that is a problem in itself but thought it necessary to at least mention it. I checked, or at least tried to check the resistance at the ballast resistor today and got nothing. Engine was not running at the time. The test probes were on the end fixing screws. Shouldn't I have seen a reading in the order of 1.6 ohms or such? Did I miss something here? Somebody point me in the right direction on this and any other resistance or voltage check I might do. Lastly, I understand that this engine should have an "091" ignition coil so, due to the fact that I have some aftermarket replacement how do I know if it is "right" for my application. thanks in advance Blake
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Re: Ballast resistor L84
You should have gotten a reading on the order of 1.6 ohms if it is a Delco resistor. The other option would be a reading of about .3 ohms which was used on previous models with a different coil. Assuming your resistor hasn't been by-passed, it has to be making a circuit in order for the engine to run. Ohmmeters can be finiky sometimes. Is this a digital meter or analog? If analog, has it been "zeroed"? I assume you touched the two probes and got a reading of infinity before starting toverify the function of the meter. You might also try a different range. -
Re: Ballast resistor L84
You should have gotten a reading on the order of 1.6 ohms if it is a Delco resistor. The other option would be a reading of about .3 ohms which was used on previous models with a different coil. Assuming your resistor hasn't been by-passed, it has to be making a circuit in order for the engine to run. Ohmmeters can be finiky sometimes. Is this a digital meter or analog? If analog, has it been "zeroed"? I assume you touched the two probes and got a reading of infinity before starting toverify the function of the meter. You might also try a different range.Comment
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Re: Ballast resistor L84
SHP and FI in 1964 used the "low ohm" ballast along with the 091 coil. This combination resulted in more primary current for more ignition energy, but was tough on points, and it's possible to get stranded from burned points. It happened to me once with my SWC as it also has the low ohm ballast.
Since the nomimal resistance of your ballast is only about 0.3 ohms, it's unlikely that a conventional analog meter, even with a "times one" scale will give you anything but zero, but a digital ohmeter - even an inexpensive one should give you a valid measurement, and it should be close to 0.3 ohm. Make the mmeasurement with the engine off and one (either one) of the ballast leads disconected so it is isolated from the circuit.
In early 1963 ALL Corvettes used the low ohm ballast and 091 coil, but the problem with burned points led to a running change. The 250 and 300 HP engines were switched to the conventional 1.4 ohm ballast with the 087 coil, but SHP and FI engines continued with the 0.3 ohm ballast and 091 coil. This is documented by the change record on the AIM that references the coil and ballast.
Use of the 0.3 ohm ballast and 091 coil continued on point ignition SHP and FI engines through 1965. Beginning in 1966 all point ignition systems were equipped with a 1.4 ohm ballast and the 202 coil.
As I stated earlier, I would recommend that you keep a spare set of points in the car with a screwdriver to change them. You can take a used set, install and adjust them, then remove them. If you have to reinstall them the dwell angle should be close to spec. Also, with high revving SHP/FI engines I recommend the high breaker arm tension point set, such as the Borg Warner A112P.
DukeComment
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Re: Ballast resistor L84
SHP and FI in 1964 used the "low ohm" ballast along with the 091 coil. This combination resulted in more primary current for more ignition energy, but was tough on points, and it's possible to get stranded from burned points. It happened to me once with my SWC as it also has the low ohm ballast.
Since the nomimal resistance of your ballast is only about 0.3 ohms, it's unlikely that a conventional analog meter, even with a "times one" scale will give you anything but zero, but a digital ohmeter - even an inexpensive one should give you a valid measurement, and it should be close to 0.3 ohm. Make the mmeasurement with the engine off and one (either one) of the ballast leads disconected so it is isolated from the circuit.
In early 1963 ALL Corvettes used the low ohm ballast and 091 coil, but the problem with burned points led to a running change. The 250 and 300 HP engines were switched to the conventional 1.4 ohm ballast with the 087 coil, but SHP and FI engines continued with the 0.3 ohm ballast and 091 coil. This is documented by the change record on the AIM that references the coil and ballast.
Use of the 0.3 ohm ballast and 091 coil continued on point ignition SHP and FI engines through 1965. Beginning in 1966 all point ignition systems were equipped with a 1.4 ohm ballast and the 202 coil.
As I stated earlier, I would recommend that you keep a spare set of points in the car with a screwdriver to change them. You can take a used set, install and adjust them, then remove them. If you have to reinstall them the dwell angle should be close to spec. Also, with high revving SHP/FI engines I recommend the high breaker arm tension point set, such as the Borg Warner A112P.
DukeComment
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Re: Ballast resistor L84
Thanks Duke, I have a digital voltmeter. When I checked the BR in the car both leads were conected. Could this be the reason for a faulty reading? BWComment
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Re: Ballast resistor L84
Thanks Duke, I have a digital voltmeter. When I checked the BR in the car both leads were conected. Could this be the reason for a faulty reading? BWComment
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Re: Ballast resistor L84
Possibly. With the ignition switch off, the circuit should be open in the other direction, but it's always best to disconnect one lead to be sure that the component is isolated. The other issue could be the sensitivity of your meter. You should check the booklet to make sure it will measure to 0.1 ohm or less. If its sensitivity is only one ohm, then it will probably read zero on the 0.3 ohm ballast.
DukeComment
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Re: Ballast resistor L84
Possibly. With the ignition switch off, the circuit should be open in the other direction, but it's always best to disconnect one lead to be sure that the component is isolated. The other issue could be the sensitivity of your meter. You should check the booklet to make sure it will measure to 0.1 ohm or less. If its sensitivity is only one ohm, then it will probably read zero on the 0.3 ohm ballast.
DukeComment
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Re: Ballast resistor L84
Thanks again Duke, Always appreciate your help. BlakeComment
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Re: Ballast resistor L84
Thanks again Duke, Always appreciate your help. BlakeComment
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Re: Ballast resistor L84
The resistance of a ballast resistor is temperature dependent by design. Isolate the resistor by disconnecting it and measure the resistance at 75 degrees F. It should be close to 0.3 ohms.
Dale.Comment
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Re: Ballast resistor L84
The resistance of a ballast resistor is temperature dependent by design. Isolate the resistor by disconnecting it and measure the resistance at 75 degrees F. It should be close to 0.3 ohms.
Dale.Comment
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Re: Ballast resistor L84
Thanks everyone for the infor on the ballast resistor. Now, what about the coil? My application calls for the 091 which I have not been able to locate for a reasonable amount of money. Question is what is the difference between that particular coil and one of the others Delco manufactured; ie 202 ect? Is there some voltage measurement one can make at the coil to determine if the coil is operating up to standards. Does the coil need to be matched to the ballast resistor for max performance? Since I don't have the 091 coil (aftermarket replacement) what specs should I be looking for?Comment
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Re: Ballast resistor L84
Thanks everyone for the infor on the ballast resistor. Now, what about the coil? My application calls for the 091 which I have not been able to locate for a reasonable amount of money. Question is what is the difference between that particular coil and one of the others Delco manufactured; ie 202 ect? Is there some voltage measurement one can make at the coil to determine if the coil is operating up to standards. Does the coil need to be matched to the ballast resistor for max performance? Since I don't have the 091 coil (aftermarket replacement) what specs should I be looking for?Comment
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