Ground Wire Plan for 408w build

[Sean D 31]

All,

Can you guys confirm or pick holes into my grounding plan for my 408w build please? 69 Mach 1 and Battery is in the engine by in stock location.

Running a PA Performance 95A 3G Alternator with their 1G-3G Conversion kit (fake voltage regulator and 3G wiring), and a 4 AWG 200 amp fused positive charge cable from alternator to the battery side of solenoid. Another 4 AWG positive from battery side of solenoid to the positive terminal on battery. 

Using the alternator wiring harness shown in picture, I will cut off the 1G connector and connect it to the 1G-3G Conversion kit, as per kit instructions.

The large ring ground connector on the alt harness will connect to engine block bolt where I will also connect a 4 AWG ground cable that goes to the battery negative terminal. The small ring connector I can either cut off or connect it to the alternator housing. Wouldn't hurt to connect to alt housing right?

Engine will be ground to chassis from the passenger side aluminum head bolt to the stock ground hole on the firewall with another 4 AWG ground cable.

Is this all I need for proper flow? Or should I use larger ground wire such as 4 AWG from alt  to engine block? Would it hurt or is it over kill to run another 4 AWG ground cable from side post negative battery terminal to chassis under battery tray?

[RPM 1,190]

Two good grounds like you, and I, have should be enough. But another wouldn't hurt, and too much is not enough. 

[1969_Mach1 333]

Aside from grounds, I'd consider not installing the fake regulator.  It's obvious the alternator is not a stock type.  So no need to mimic a stock voltage regulator.  Then you can clean up the wiring a little in that area.

[Sean D 31]

So you all think that the ground wire in the alt harness (ring connectors), between the alt and engine is large enough for 95Amp 3G alternator? 

Also is the 4 AWG ground wire between head to firewall, and 4 AWG from engine block to negative terminal on battery enough or should I add a ground from battery terminal to the chassis?

[Vicfreg 771]

I would also not use the fake regulator.   I typically run a ground wire (#4) from the starter to block bolt to the frame.   I am not a fan of firewall grounds, the metal is thin, and typically people use sheet metal screws or self tapping screws that can come loose.  The starter is where all the current flows, it is by far your biggest amperage draw.   

The negative battery terminal to engine block is also fine.   That should work out well.

The in line (MIDI) fuse is essential, so good job there.

I am running a 140 amp alternator with a trunk mounted battery, so mine is a bit more complicated.  You can look at my build thread to see the details.

Good luck!

 

[Sean D 31]

1 hour ago, Vicfreg said:

I would also not use the fake regulator.   I typically run a ground wire (#4) from the starter to block bolt to the frame.   I am not a fan of firewall grounds, the metal is thin, and typically people use sheet metal screws or self tapping screws that can come loose.  The starter is where all the current flows, it is by far your biggest amperage draw.   

The negative battery terminal to engine block is also fine.   That should work out well.

The in line (MIDI) fuse is essential, so good job there.

I am running a 140 amp alternator with a trunk mounted battery, so mine is a bit more complicated.  You can look at my build thread to see the details.

Good luck!

 

Thank you very much for the suggestion on grounding the starter! Great idea. Assuming you are running a 3G Alternator, did you run any specific ground wire from the alternator to block and/or directly from alternator feed wire harness to alt?

[Midlife 814]

1 hour ago, Vicfreg said:

I would also not use the fake regulator.   I typically run a ground wire (#4) from the starter to block bolt to the frame.   I am not a fan of firewall grounds, the metal is thin, and typically people use sheet metal screws or self tapping screws that can come loose.  The starter is where all the current flows, it is by far your biggest amperage draw.   

The negative battery terminal to engine block is also fine.   That should work out well.

The in line (MIDI) fuse is essential, so good job there.

I am running a 140 amp alternator with a trunk mounted battery, so mine is a bit more complicated.  You can look at my build thread to see the details.

Good luck!

 

You need a ground wire to the firewall or some other place on the chassis.  This provides a ground for the rest of the car, e.g. instrument cluster, lamps on the outside of the car, etc.

[Vicfreg 771]

I am running a 3G alternator.  There is one wire, and in my car, it goes to my engine bay power distribution block.  The alternator is bolted to the engine, and the engine is grounded to the frame.  So, no other grounds needed.  

Do your 3G alternator instructions indicate there should be a dedicated ground?

[Sean D 31]

10 hours ago, Vicfreg said:

I am running a 3G alternator.  There is one wire, and in my car, it goes to my engine bay power distribution block.  The alternator is bolted to the engine, and the engine is grounded to the frame.  So, no other grounds needed.  

Do your 3G alternator instructions indicate there should be a dedicated ground?

No it does not but I have read that some people put a ground from alt to engine block for good measure/just in case.

[Sean D 31]

12 hours ago, Midlife said:

You need a ground wire to the firewall or some other place on the chassis.  This provides a ground for the rest of the car, e.g. instrument cluster, lamps on the outside of the car, etc.

I will run a stock ground wire pictured below from passenger side rear block to firewall. Then the 4 AWG negative cable front passenger side front to negative terminal to battery. I will also probably run a 4AWG ground from starter to block and back to chassis frame as Vicfreg suggested. Guess more is better when it come to grounds. Sound good?

Vicfreg - where did you connect the ground on your starter? one of the bellhousing/starter bolts?

[Bob & Sue 110]

One other thought is to make sure wherever the ground wires are bolted on be sure to sand & clean the area of contact don't just rely on the bolt threads for a solid ground, then touch it up with some engine bay paint & cover it with dielectric I like using grounding blocks it gives you more connections in the future.

I have a set of 16' Fluke cables that I can reach any point on the car to check continuity from all grounding points. I went through the car making sure I had continuity from neg battery  to every grounding point I could find, I found several with poor connections. 

A bit off topic our last boat the PO had connected 12v grounds to the bonding side (120 volt system) & 120 volt grounds to some 12v grounds this led to stray current in the water when plugged into shore power which could have killed someone in the water or me in the bilge if there was water present. It took me several days of sorting out wires to get it correct.  

4 AWG wire is plenty for your system here's a good calculator to to determine amp loss of anysize wire.

http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.8152&voltage=12&phase=dc&noofconductor=1&distance=10&distanceunit=feet&amperes=60&x=86&y=18

[Vicfreg 771]

Agree with Bob and Sue.  I do a resistance check on all my grounds with my Fluke and a continuity check on all my terminations.  Especially with these new digital systems, good grounds are vital.  

[Sean D 31]

11 hours ago, Vicfreg said:

Agree with Bob and Sue.  I do a resistance check on all my grounds with my Fluke and a continuity check on all my terminations.  Especially with these new digital systems, good grounds are vital.  

Vicfreg - where did you connect the ground on your starter? one of the bellhousing/starter bolts? Picture is worth 1000 words.

[Vicfreg 771]

To the starter to bellhousing bolt.  I took the picture of where I install it, but in this picture, the ground wire is not installed. The pic shows a C-4 bellhousing.

 

[Sean D 31]

11 hours ago, Vicfreg said:

To the starter to bellhousing bolt.  I took the picture of where I install it, but in this picture, the ground wire is not installed. The pic shows a C-4 bellhousing.

 

Excellent, thank you!