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Old 07-06-2009, 03:06 PM   #1
Reno67
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Default Help with MSD 6AL w/Mallory HEI Distributor

Hello, I need some help from the experts. I am a noobie to these fancy ignition systems, so sorry if this is a dumb question. I searched the forum and could not get the information I needed (or couldn't understand what I was reading).

I just recently bought a 78 vette with 350 (L-48) rebuilt to a 383 stroker. It has an MSD 6AL that feeds a Mallory 8548201 HEI Distributor (the one with the coil in the top cover).

I believe the MSD fried (it was hot as fire and I smelled a scent like burnt circuit boards from it). The car was running perfectly, then just died and shut off on the interstate (fyi, the engine was not running hot, about 180deg). It turns over but will not start anymore. No spark is getting to the plugs.

I have removed the MSD 6AL box and was wondering if there is a way to just run off of the Mallory HEI distributor without the MSD. I would like to just keep the Mallory and not have a MSD type box if possible. The Mallory does have two wires coming out of the side of it that the MSD plugged into. It looks like the unit on the Mallory website for the 8548201C, but only has two wires (purple and green) coming out of the side instead of 3 as shown on the site.

I guess the main question is will it be possible just to run with the Mallory distributor, or do I need to replace the distributor (or add back some type of ignition box (MSD, crane, mallory). If it is possible, a wiring diagram or links to wiring diagrams would be helpful. Also, any info on any another components for the Mallory distributor that I will need to buy would be helpful.

The vette is for weekend driving only.... no racing. According to the guy I bought it from, the car needs 93 octane gas, so I don't think it is too high a compression (maybe 10.5 to 1).

Thanks for the help and sorry for the length of the post.
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Old 07-06-2009, 04:44 PM   #2
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There's no reason you can't run with just the Mallory HEI. For a street car there's no real advantage to having the capacitive discharge box anyway. You might find better starting but that's about it.

Disconnect the MSD, remove it and the wiring, make sure the HEI wiring is correct, and enjoy driving.
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Old 07-06-2009, 04:55 PM   #3
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Thanks for the reply. That is what I thought. I do not have the documentation for the Mallory HEI, so I am also looking for info on how to wire it up without the MSD box. The Mallory site instructions are too vague for me. Thanks.
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Old 07-06-2009, 07:09 PM   #4
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If no one can supply the answer to your wiring question you can call Mallory - they have good phone tech.s.
iHere is a quick way to solve the MSD misery:
1) Wire the Mallory to make the vehicle start and run.
2) Place MSD box on floor just behind the left rear tire.
3) Position your self in the drivers seat and with engine idling move gear selector to "R".
4) Listen for satisfying crunching / crackling sound.
5) Stop vehicle after 10' of travel.
6) Crack open cold barely / malt / hops beverage.
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Old 07-07-2009, 01:55 PM   #5
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Bump to the top. Also, does the tach wire go to the terminal labeled "coil" on the mallory distributor cap? Mine does not show a "tach" terminal.... just a "Batt", "ground", and "coil". Thanks.
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Old 07-07-2009, 03:09 PM   #6
Duke94
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If your MSD dizzy is like mine (Mine is a 8365 Pro Billet), you will need the module that goes inside the dizzy. On the cap connections, the +12VDC goes to the "BAT" terminal, and the Tech goes to the "TACH" terminal. Then there should be a 3 wire cable that goes from the remaining 3 terms on the cap to the module inside the dizzy. See below.

Gary

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Old 07-08-2009, 08:01 AM   #7
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Thanks for the info and diagrams. This helps alot.
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Old 07-08-2009, 08:54 AM   #8
jackson
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Most coil-in-cap HEI ... MOST of em ... all I've seen ...

... there're 2 wires (trigger wires) coming out of pickup coil and going to HEI module. One Green and one White. Green is Inboard & White is Outboard. Those are the 2 wires that get connected to msd 6 box when module is bypassed/removed.

If you need a new harness from module to cap ... that's probably still available from local parts store that sells "Standard Ignition" branded parts ... I don't recall the p/n ... same if you need a new pickup coil, ignition coil, module etc.
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Old 07-08-2009, 10:58 AM   #9
Dantana
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Quote:
Originally Posted by Reggie Dunlop View Post
If no one can supply the answer to your wiring question you can call Mallory - they have good phone tech.s.
iHere is a quick way to solve the MSD misery:
1) Wire the Mallory to make the vehicle start and run.
2) Place MSD box on floor just behind the left rear tire.
3) Position your self in the drivers seat and with engine idling move gear selector to "R".
4) Listen for satisfying crunching / crackling sound.
5) Stop vehicle after 10' of travel.
6) Crack open cold barely / malt / hops beverage.
Been here...
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Old 07-08-2009, 10:58 AM
 
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