Ballast Resistor: Need Help!

[Ray C.]

I rebuilt my 61 270HP engine during the frame off restoration process. The resistor that was on the engine was in very poor condition (many cracks) and I replaced it with an after market reproduction replacement resistor (. 3 ohm) which should be correct for the high performance engine. With this resistor the left set of points would burn out after a few hours of run time. After replacing three set of points, I replaced the resistor with an over the counter generic resistor (.8 to .9 ohm). I am still using this resistor at the current time and have about 500 miles on this resistor. I have just purchased an original GM# D111 1931385 resistor and would like to install it on the 1961. I measured the resistance and it is .3 ohm. Why would the original resistance specifications cause the points to burn with such short run time and what needs to be corrected to use the original resistor? The coil is an #091 coil.

Thanks Ray
#36314

[Duke W.]

Re: Ballast Resistor: Need Help!

The lower the ballast resistance the higher the primary current, and high primary current can burn points. This was not an uncommon problem with the 0.3 ohm ballast, but not every two weeks, so I wonder if today's points are poorer quality.

On dual point distributors one set of points opens/closes slightly ahead of the other, so the last set to open sees high current and arcing.

A leaky condenser can also cause point burning, so make sure your condenser is okay. Since they are tough to test (other than shorted) just install a new one,and make sure it is correct for the dual points dist. I'm not sure if they used a different capacity condenser than the single point distributors,

Burned points was a common malady with the .03 ohm ballast and Chevrolet wrote a TSB in 1963 recommending the "standard" 1.8 ohm ballast, especially in cold weather, and stopped installing the 0.3 ohm unit on all but SHP/FI engines and finally abandoned it after '64.

I also recommend you run the standard 1.8 ohm ballast, which should stop burning points. The lower primary current will mean a little less per spark ignition energy, but if the plugs and wires are in good shape, it should not result in less performance due to misfires.

There was another thread on this issue within the last week, so you may want to scroll down and read it.

Duke

[Ray C.]

Re: Ballast Resistor: Need Help!

Thanks Duke

Ray

[Doug Flaten]

Re: Ballast Resistor: Need Help!

I had a similar problem with the points. I used to replace them every 2000 to 3000 miles on my 61 270 HP and it made a noticeable improvement in the performance each time. I was always stumped by the fact that the points were not pitted or blued like they were burning. I eventually hooked up an MSD box and blocked off one set of points. The remaining points carry very little current and are used to trigger the MSD. I have not changed the points now in 8 years or so and my spark plug maintenance from the rich carburation has dropped to nothing.