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Discussion Starter #1
On my 65 289, I have the ground cable running from the battery to the engine block. It is grounded at the same location as the alt ground.

The second ground is from the right cylinder head to the firewall. That ground cable is pretty small and grounds at one of the screws that holds the brake line to the firewall.

I dont think that second ground is adequate.

Im thinking about running a third ground from the block to one of the sway bar bolts. That doesnt require any holes to be drilled.

Will that do the job, or do I need to increase the size of the ground wire from the head to the firewall?

I have a new alt harness and a new set of battery cables.
 

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I added a ground from battery directly to chassis. Still have battery to block and head to chassis grounds in place. I think doing battery to chassis is a better solution and easier in my opinion. Will you/I see any difference? Probably not, but I added a lot of electrical devices/mods and just thought a more direct ground path was cheap insurance.

Edit: my battery has side posts though. A must have for me as several items run power direct to battery.
 

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I did exactly what you described. It works great.
744944
 

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Keep the firewall to cylinder head, so you have a good ground for temp and oil pressure gauges.

The firewall is connected to instrument cluster ground.
 

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Just replace your block to chassis ground with a larger cable. A woven ground strap works well as it can flex easily.
 

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I'll add a funny story here. In my younger says I put the battery in the truck of a '65 fastback and bolted the ground cable directly to the truck floor. I ran a big thick welding cable from the battery to the starter solenoid. Got in the car started cranking the engine and smoke started pouring off the manual choke cable? I didn't put two and two together and rushed to the engine compartment and grabbed the choke cable. Now I know what a branded cow must feel like. My hand had ended up with tiny charred lines on it like a grilled hot dog. What I did not realize at the time (I was 16) is the entire drivetrain is completely insulated from the body. The engine and trans mounts are mounted on rubber. The rearend is bolted to springs that are insulated with rubber bushings. The only ground path all the starter current could find was through the small wire from the head to the firewall and the manual choke cable.

If your restoring the car use the original style cable from the head to the firewall If not get one of the woven flexible ground straps.

This is a little advanced but if you do a "voltage drop test" using a digital voltmeter across individual ground connections and ground wires it will locate any unwanted resistance that could cause problems. If your interested in making your look up voltage drop test on Youtube. It is the best way to diagnose ground problems and locate voltage drops that are not yet bad enough to cause problems. It is one of the most useful tests you can perform with a voltmeter.
 

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I forgot. always use a star washer under "all" ground connections. It bites into the metal on the car and the terminal on the wire. There is almost always one from the factories on ground wires. They get lost and not replaced because people do not understand their purpose. They are made to poke through any paint that could insulate the connections. You should be scraping that spot down to bare metal anyway.

745006
 

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Just replace your block to chassis ground with a larger cable. A woven ground strap works well as it can flex easily.
I've got one of these from the rear of the right cylinder head to the firewall and works perfectly.

745019
 

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I am now grounded on how to properly ground.
 

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IMHO, no such thing as too many ground connections. But be sure that the various ground connections have a good contact.
One other issue can be the battery cables. They may look good but have corrosion inside which results in electrical resistance. Ask me how I know. Battery cable pulled right out of the clamp due to internal corrosion.
0622191530.jpg
 

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1965 Mustang Fastback GT350-Tribute Restomod. 2019 Shelby GT350.
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I don't disagree that the star washers can generally provide an adequate connection - especially if you want to cut through paint, oxide or other contaminant. However, if you are building a ground pathway to pass a high current, this type of washer creates a relatively higher resistance because it reduces the electrical contact area to those points which dig into the chassis and the cable connector.

The best (lowest-resistance) connection is one which maximizes the electrical contact area. This would be a broad cable connector along with a flat washer against the chassis or firewall. During installation, the contact areas must be clean, bare metal and the connection must be properly torqued for adequate compression. Covering the completed joint area with a dab of dielectric grease will help prevent fretting and oxidation.
 

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Covering the completed joint area with a dab of dielectric grease will help prevent fretting and oxidation.
Silicone Di-electric grease is an insulating product and shouldn't be used on electrical connections. It SHOULD be used inside spark plug boots, rubber grommets, etc. For electrical conductivity, use "bulb grease" or a conductive grease.
 

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These cars worked fine from the factory with the grounds built into their design. Make sure your cables and connections are good and you should be good to go. Extra grounds won't hurt though.
 

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Silicone Di-electric grease is an insulating product and shouldn't be used on electrical connections. It SHOULD be used inside spark plug boots, rubber grommets, etc. For electrical conductivity, use "bulb grease" or a conductive grease.


uh oh...I have a tube of that di-electric grease and have smeared it on connections such as the ground contacts. I also added a ground from the block to the right motor mount apron bracket. Guess I will look for some bulb or conductive grease at the next parts store I go in....Learn something new every day!
 

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Hi Bart, I was proposing that dielectric grease be applied to the electrical connection after it was completed - not used in between the electrical joint components. My intent was to apply a barrier to moisture and oxygen to slow corrosion of the finished joint. I'm not sure if my wording was unclear or perhaps you might suggest a different product or technique to protect a bare electrical connection? Thx! Jim
 
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Hi Bart, I was proposing that dielectric grease be applied to the electrical connection after it was completed - not used in between the electrical joint components. My intent was to apply a barrier to moisture and oxygen to slow corrosion of the finished joint. I'm not sure if my wording was unclear or perhaps you might suggest a different product or technique to protect a bare electrical connection? Thx! Jim
Sure. That'll be fine. Me, myself and I like the CRC battery terminal protector... the aerosol sticky red stuff as it gets a lot harder than silicone gel.
 

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Good timing on this post, I just ordered a new engine to firewall ground wire. Chasing down why my battery keeps puking. I’m on my 3rd voltage regulator (now a motorcraft) and have changed out all the wiring under the hood, including battery and alternator.
 

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Discussion Starter #20
Where does the ground bolt to on the firewall?

Mine is on one of the clips that hold the RF brake line. I dont see anywhere else it could go.

I bought a 3-cable battery wire set from CJ Pony.

Im going to leave the head to firewall ground as is. The 4ga ground will go from the block to the frame.
 
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