OK, here is what is going on. Last year, my car ran perfectly. This year, all I did was change the ignition coil, (went to the one recomended by MSD for my 7 pin GM HEI ignition in my 62 corvair), and now when I get to around 3850, the tach will go nuts, just a little, and the car misses when that happens. Under load, it seems to be a little less than just cruising, but still happens. I am going to talk to MSD, to see if they think the low resistance of the coil could possibly be the problem, (very small distributor cap not made for HEI). I suppose the best test would be to through the old coil back in and see if the problem goes away. Anyway, I did do a data log, I was wondering if any of you who know more about this than me could look at it. I took a look and the RPM would go from 3800 or 3900 to 9000 or so! (obviously only in the log, I WISH I had engine responce like that!). What really surprised me was the timing. I would think that perhaps the timing would go nuts at the same time, but it did not. Yet, I did see a couple times the timing went down to 9 degrees, just for an instant, with nothing else looking strange on the data log.
Like I said, if someone could look at the log and see if they see anything MS related that may be the problem, that would be great.
Thanks!!!
MS 1 with V 3.0 board
Wild RPM problem only at 3850 and above
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64Vair
- Helpful MS/Extra'er
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- Location: Detroit Michingan Area
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Problem solved
Called MSD and the guy had a good idea of what it was right away. He suggested that it was noise. I had thought of that, but went through great pains to prevent noise, put ECU within 24 inches of battery, shielded cable for tach, etc. Well, when I looked at my installation, and thought about it, I realized the problem. The coil was mounted on the outside of the enclosure that held the module. They were inches apart. So I put a metal plate under the coil and grounded it. I then drove the car and while it still had the problem, it was less trouble and started at higher RPM. So I made an enclosure that goes completely around the coil, and ground it to the plate under the coil. The problem has gone away. The ONLY time I get ANY hint of noise, is when I lift at around 4500 or 5000, I get just a split second of noise, and that is it. But I must be a WOT and then lift. Under ANY other driving it will not do it.