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| Installing a MSD 6AL with a petronix stich | Rate Topic |
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| Posted: 07-26-2020 12:07 pm |
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1st Post |
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discogodfather Member 
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Pretty straight forward stuff in terms of the install of an MSD 6AL unit (this is the newer version with the built in rev limited that you tune with some wheels). Here is the MSD diagram for the install:  Everything looks good but what about the tachometer. Tried called MSD and they put me on hold for 3/4 of a hour. My big question is- will this run my stock Smiths tach if I wire it up like this. I almost know the answer to the question is NO. So then do I need another scheme, possibly with the gray tac output wire? I also found some people called out for a 8910 or 8929 unit to get the right signal to tach, but how that would work is beyond me. Anyone have this project done? I sure would love for this thing to just use the stock tach setup.
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| Posted: 07-26-2020 08:46 pm |
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2nd Post |
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Tom Bradley Member
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Never mind. What I was thinking will not work. If the system will not trigger the tach as is, I think you will be stuck unless the guys at the MSD manufacturers have some ideas. The problem is that there needs to be enough current flow change from the Pertronix being on and off for the tach to trigger. And that will depend on what kind of load the MSD unit puts on the Pertronix. Last edited on 07-26-2020 09:57 pm by Tom Bradley |
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| Posted: 07-26-2020 09:26 pm |
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3rd Post |
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Tom Bradley Member
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Last edited on 07-26-2020 09:51 pm by Tom Bradley |
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| Posted: 07-27-2020 12:06 pm |
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4th Post |
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subwoofer Member
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Converting the tach with one of these: https://www.spiyda.com/smiths-rvi-rvc-conversion-board.html is probably the best option. Has the positive side effect of reducing voltage losses to the coil and increasing reliability since you can eliminate several plug connections on the way from the ignition switch to the coil. -- Joachim
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| Posted: 03-10-2021 08:40 pm |
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5th Post |
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Distributorguy Member
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The 6AL actually steals power from your HT ignition and won't result in more power produced. I've done the back-to-back dyno testing. If you want to upgrade to the MSD 7-series box, you'll gain power. 4 cylinders, especially small displacement ones, don't lack dwell time so adding multiple sparks is really just a trick. You need longer spark dwell, not shorter via capacitors in the MSd box. If it won't fire your tach, then its not firing your coil properly either. Glitchy Chinese junk. Sorry.
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| Posted: 03-11-2021 03:30 pm |
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6th Post |
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noomg Member
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Disco, I installed an MSD with the Pertronix ignition several years ago and had the same problem you have, the tach wouldn't work. I found the remedy in the MSD install instruction booklet. It recommended purchasing a Chrysler dual ballast resistor that was used from '73 to '76. I installed it as per directions and it's been working ever since. I did mine 20+ years ago and my instruction booklet is dated 6/97. You probably have a newer book which may not have this information included. The install was a snap, MSD switched red to one side of the ballast resistor, MSD white from dizzy to the other. To get the B/R I simply went to a Chrysler dealership and got one from the parts dept. Unfortunately that option is not open to you, you'll probably have to find it aftermarket. Also, I believe it was used on their vans.
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