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I’m currently wiring the charging system of my ‘78 after an engine swap to a 383 Stroker and am running a modern GM 4-pin alternator. If I need to bring in the starting system into this convo I will and can draw up a new diagram to include it if needed (I’m running an MSD HEI with an external MSD 6AL ultra). Anyways, the attached image is what I drew up based off what I’ve set up so far. The main thing is that the OEM BAT wire provides power to several other components, is it okay to just connect it to the BAT post along with the what I already have connected so I can get power to all my dash and whatever else it hits? I have plans to build a full wiring harness for the car down the line, but for now I’m just trying to get it running for the first time with this swap and be able to drive it safely while I work on building a new harness
Last edited by Parker Langley; Feb 4, 2026 at 05:48 AM.
Exactly how you wire it, and the size of wire needed will depend on which alternator your running. I highly recommend a 3 wire alternator over a one wire alternator.
Higher than stock output alternators require heaver wiring,
I highly recommend you go to "Mad Electrical's " Web site. Go to their tech pages and read all the articles about the differences between alternators and all about how to correctly wire them. There tech pages are written so an average guy can understand them. Really worth your time to have a look.
I'm pretty sure I'm running a 3-wire (part number on bottom of diagram) and I was reading through all of M.A.D's articles when I started to doubt my setup because of how he has the "New Chevy System" set up. Do you know if he's still in business? I tried to call to talk about it but the call wouldn't go through. I just need some outside perspective because 1) I'm learning as I go and 2) I'm really getting in my own head about it cause I've been spending hours looking at wiring diagram's
I see you included a part number. But that means nothing to me. I also see you've included a adaptor of sorts on the 2 wire connector. Which I don't understand.
Are you not running a 12SI style alternator?
It's not a 12si, I put the part number so you can look and see exactly what it is. It's a 4-pin GM Alt, same as the C7 corvettes. I'm running Holley's "Small Block Chevy Mid-Mount Complete Accessory System". It's all the same as you'd find on an LT1
Last edited by Parker Langley; Feb 3, 2026 at 10:55 PM.
I see, sorry you just didn't put down modern GM 4 pin Alternator straight away.
There is a guy on here who is always jumping on every Alternator thread recommending that people run the modern Alternator. Hopefully he'll see this thread as well and shine some light on it for you.
That looks like the Holley version of a $50- junkyard alternator, or $150- new. The 4-pin is the older Delphi alternator common on GMT800 trucks, and Gen III LS engines. C6s and C7s have 2-pin alternators, and allow for direct output control with a PWM signal. It will work just fine, but wow, Holley is proud of their stuff. $300- for some black paint is pretty steep. If you can find a DR44G alternator instead, you'll be a bit more future-proof.
Here's another aftermarket example, for a C7, with a 2-pin regulator.
Parker Langley
I used a 2-pin DR44G alternator on my 68. Normally PWM controlled by ECM....but have a few options to otherwise control it. Common as all get out later model GM vehicles.
Here is my thread ..... it has some to do with fabricated a mount (which you don't need to worry about) but it also mentions options on controlling the alternator. My favorite alternator so far and I've gone from a 10DN(?) externally regulated, to a 94 amp 12si, to a 140 amp CS-144, and now this DR44G---- the DR44G is the first alternator where I've a little bit of voltage regulation control.
There is info within on how I ended up controlling it and feedback from folks who know more than I do about the VR control: https://www.corvetteforum.com/forums...xperiment.html
Yes, I already have everything installed, the last thing I have to do is wiring the starting and charging systems. Is it not okay to connect the oem power wire along with the 2AWG wire? I wanna make sure power is getting everywhere in needs to through the dash. If the pigtail red is enough to make that happen then I'll leave it disconnected. And is it okay to connect the oem red wire on the starter?
Parker Langley
do you have a 1978 wiring diagram?
the simplest thing to do (to just get going) would be to check that and make sure everything is in place.
If the 78 came with the typical fusible links then they will open before any damage happens to the main wiring.
Originally Posted by Parker Langley
Yes, I already have everything installed, the last thing I have to do is wiring the starting and charging systems. Is it not okay to connect the oem power wire along with the 2AWG wire? I wanna make sure power is getting everywhere in needs to through the dash. If the pigtail red is enough to make that happen then I'll leave it disconnected. And is it okay to connect the oem red wire on the starter?
If you run the 2 AWG wire back to your battery, you should not run the stock wire from the alternator to the starter. Or, you could just run 2 AWG to the starter.
I'd consider fusing it either way, at the battery, or at the starter. @Richard454 has put out similar diagrams. He clued me into these Blue Sea Systems fuse blocks, which is what I use.
Do the MSD instructions insist on pulling power directly from the battery?
Yeah, the 6A box runs power straight from the battery. I have my 2AWG wire fused at the batteryand then theres whatever fusible links are present throughout the system original system (If I run it)
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Charging system wiring
