HEI rotor button differences..

[marco_1978_spyder]

I have 2 HEI brushes. I think one of them may be a low resistance one.

Like this one here.. http://www.classicindustries.com/firebi ... 20900.html

""ACCEL HEI IN-CAP COIL LOW OHM CONTACT BRUSH
The standard OE carbon brush in GM's HEI in-cap coil distributor has a very high (5k to 10k Ohms) resistance. When an aftermarket capacitive discharge ignition system, such as an ACCEL, Mallory, Crane, Holley or MSDunit is installed, this high resistance can create enough heat to melt the distributor cap.

ACCEL's low Ohm contact brush solves this problem because it passes virtually all the energy to the rotor without causing excessive heat build up."

I'm using an in-cap higher voltage coil... would this low resistance brush be necessary? I suppose I'll need a cheap voltage tester..


Ok- Electrical guru's..

Here are the OHM readings I got, which one has less resistance?

#1

Ohm Setting / Digital readout:

200 / 03.2

2000 / 002

20k / 0.01

200k / 0.00

2000k / 0.00

#2

200 / 1 (same as open test leads)

2000 / 1

20k / 2.93

200k / 2.9

2000k / 003

Thanks for your help!

[ROB]

Good knowledg , didn't know about this. Hell, I'd use the low resistance one even in the stock setup. What couldit hurt? But yet sounds necessary in a performance setup.

[marco_1978_spyder]

Ok- Electrical guru's..

Here are the OHM readings I got, which one has less resistance?

#1

Ohm Setting / Digital readout:

200 / 03.2

2k / 002

20k / 0.01

200k / 0.00 (same as test leads touched together)

200M / 0.00

#2

200 / 1 (same as separated test leads/ full resistance)

2k / 1

20k / 2.93

200k / 2.9

200M / 003

Thanks for your help!

[spencerforhire]

#2 is the lower resistance one. Think of it like this; when the meter leads are touching, the theoretical resistance is zero. A perfect path for the current to flow. When the leads are not touching, the resistance is infinitely high and no current can flow.

[marco_1978_spyder]

Thanks for the reply spence.... I don't doubt you, but I'm still confused.

I re-worded my post, I might have been confusing.

So, if a lower number equates to less resistance, then looks like #1 might have less resistance to me?

Judging by the 20k results for both, and also how #2 gave a full resistance reading at 200 and 2k. While #1 had a small value.

[spencerforhire]

Yes, Mark #1 is indeed lower; your meter(cheap by your own admission) gives ambiguous readings at both ends of the scale. I'm spoiled, my big $$$ Fluke meters are auto-ranging so there's no confusion about where to set them to measure resistance. Also last night I was reading(and replying) on my phone so I mis-read your readings.

[marco_1978_spyder]

Thanks Spence! I thought I might not have been as clear as I could have, and I really wanted to sure about getting an answer that makes sense of the readings..
Thanks for checking in again, and your help here. I owe ya a beer if you make it to one of the meet's.

Ultimately, looks like I do have one low resistance brush in my possession (a $10 savings).

The low resistance one is all bright copper appearing , the higher resistance one looks like a duracell battery, dark carbon color, the end is copper.

It was 29* in the garage when I checked so I didn't stick around to take any pic's, which always makes for a better thread.

[spencerforhire]

The low resistance copper colored button is made of just that, and the black one is made from carbon which has a higher resistance. Originally installed by GM to limit interference on your AM radio. I guess that's not an issue any more; don't know about New York, but up here in Nova Scotia there's no AM stations left. What you quoted from Classic Industries earlier explains why one is better than the other; if you try to use the stock one with any kind of aftermarket ignition box or even a high output coil, that resistance creates heat in the same way an incandescent light bulb works. I have seen lots of melted HEI caps from just this scenario.

[marco_1978_spyder]

So Yesterday, going thru some drawers, I find some other rotor buttons.

1st, Another of the 'duracell' looking ones. I noticed that these ones are copper on each end. Both of them offer the highest OHM readings/ most resistance.

The dark carbon part seems to be an added on coating.

2nd, I found this all carbon one. At least I think it's carbon it's pure shiney black. Quite different from the other's.. It has a very low ohm reading/low resistance!

The final one I have is installed in the distributor currently, it was all copper and has the lowest resistance of them all.

The all carbon one is the mystery...you'd think that would be the highest resistance one. Looks like the one jeg's offer's.

The bottom one pictured is the all carbon one. Low light in the shop.