Grounding the 1972

blkulis

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Did the 1972 Ford Mustang have a engine ground strap from the engine to the firewall? Or does it really need one?? I bought the cable kit with the starter cable, positive battery cable and the negative cable that grounds from the battery to the engine. The negative cable has a bracket that looks like it should bolt to the apron.

 

CZ-75

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I believe it should be grounded to teh firewall to help the gages get a good ground too.

 

caspianwendell

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Always have a ground to the chassis from the engine

 

MechEng

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You should have several grounds, an engine block to chassis, and battery to chassis, and then a lot of guys like to upgrade the positive cable to the alternator. It's commonly called the "Big 3" upgrade, and people tend to use 0 gauge cable or larger. It's a bit of overkill, but the better your grounds the more reliable your electrical system. Make sure you clean the ground point to shiny metal first, and then if you want use some of the gel products they sell for electrical connections between your wire and the metal, this helps keep moisture out of the connection and improve the longevity of the joint.

Here's a link to a sample of this from one of the other forums I walk:

http://www.f150forum.com/f75/how-big-3-upgrade-46822/

It's for F150's, but the same fundamentals apply to our cars as well.

 
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Don C

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The original routing for the ground runs from the battery to the bottom screw on the regulator and ends at a bolt on the front of the block.

 

midlife

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The original routing for the ground runs from the battery to the bottom screw on the regulator and ends at a bolt on the front of the block.
That's only one component of the grounding system. Since the engine is mounted on rubber motor mounts, how does the chassis itself get a grounding point for all of the instrumentation, lights, etc.? You absolutely need the engine to firewall ground.

The car will "work" without it, but I have heard stories that without that ground that the crank bearings start to degrade due to electrolysis.

 

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You can never have too many grounds on an old Mustang. Ground the crap out of it. I run one ground strap from near the passenger side motor mount to the fender, there is a stock strap connecting the cylinder head to the firewall, and I have another somewhere underneath... mainly 0 gauge welding wire as mentioned in a previous post. No electrical problems, but it sure used to have them!

 

Don C

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The original routing for the ground runs from the battery to the bottom screw on the regulator and ends at a bolt on the front of the block.
That's only one component of the grounding system. Since the engine is mounted on rubber motor mounts, how does the chassis itself get a grounding point for all of the instrumentation, lights, etc.? You absolutely need the engine to firewall ground.

The car will "work" without it, but I have heard stories that without that ground that the crank bearings start to degrade due to electrolysis.
I never said the engine/firewall ground wasn't a good idea. That had already been answered, I was letting him know how the original style battery ground cable, that he bought, is connected.

 

Jeff73Mach1

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on the back upper passenger side of the block is a 3/8 ths blind threaded hole about 1" deep. I think it is ideal for a ground and probably intended to be used for a ground.

I just picked up a length of negative battery cable to add for my chassis ground. I wonder if the braided ground straps offer any advantage?

I'll have to study on this before relocating my battery to the trunk.

 

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on the back upper passenger side of the block is a 3/8 ths blind threaded hole about 1" deep. I think it is ideal for a ground and probably intended to be used for a ground.

I just picked up a length of negative battery cable to add for my chassis ground. I wonder if the braided ground straps offer any advantage?

I'll have to study on this before relocating my battery to the trunk.
Jeff,

They really don't. I spoke with my father about this who is an Electrical Engineer with 35+ years experience in DC Power. I asked him about using 0 Gauge wire versus say 16 gauge wire, or braided wire straps. He said there's really no difference between all of them. The amount of actual power that you're flowing through most ground straps is so minuscule that the gauge of the wire isn't the factor, it's more about providing a short and effective path that is important.

He added several extra ground points to his Scion Xa, as it was a popular and simple mod to do, but instead of using the HUGE 0 gauge wire that people were recommending (Because many people perceive bigger as better, because it can "flow" more) he used some 18 gauge wire that he had laying around our garage. And based on readings off an Ohm Meter, he was seeing the same positive effects the guys with the huge wire were seeing.

What you really want to make sure is that you have a quality connection to the metal, and that the cable is rather well sealed from corrosion intrusion. Corrosion and Oxygen equate to a higher resistance in the wire, and that limits its ability to flow current.

 

caspianwendell

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on the back upper passenger side of the block is a 3/8 ths blind threaded hole about 1" deep. I think it is ideal for a ground and probably intended to be used for a ground.

I just picked up a length of negative battery cable to add for my chassis ground. I wonder if the braided ground straps offer any advantage?

I'll have to study on this before relocating my battery to the trunk.
Jeff,

They really don't. I spoke with my father about this who is an Electrical Engineer with 35+ years experience in DC Power. I asked him about using 0 Gauge wire versus say 16 gauge wire, or braided wire straps. He said there's really no difference between all of them. The amount of actual power that you're flowing through most ground straps is so minuscule that the gauge of the wire isn't the factor, it's more about providing a short and effective path that is important.

He added several extra ground points to his Scion Xa, as it was a popular and simple mod to do, but instead of using the HUGE 0 gauge wire that people were recommending (Because many people perceive bigger as better, because it can "flow" more) he used some 18 gauge wire that he had laying around our garage. And based on readings off an Ohm Meter, he was seeing the same positive effects the guys with the huge wire were seeing.

What you really want to make sure is that you have a quality connection to the metal, and that the cable is rather well sealed from corrosion intrusion. Corrosion and Oxygen equate to a higher resistance in the wire, and that limits its ability to flow current.
Alternating current is the only type that requires a neutral and must be sized properly. The difference is AC requires a complete circle to complete a circuit, while DC does not as it is a direct current. With that being said, the wire grounding the chassis does not have to be huge to create a ground, but, should be no less than one size smaller than the positive for the amount of amperes that are being drawn.

 

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And that's precisely why using a stainless steel braided wire strap is commonly used: because it does not corrode as easily and will likely outlast the lifespan of the car. The conductivity of stainless steel is markedly less than copper and aluminum, though. As for the gauge of wire involved, most people go overkill (which is not bad insurance), but really only necessary when there are massive current draws from onboard electronics like a 2000 watt stereo system, electric cooling fans from hell, power hungry lighting systems, etc.

 
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Duncan Mach72

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Sorry, have to butt in here. Any electrical system whether AC or DC has to make a 'circuit' - that's why it's called that.

When you crank the engine, that exact same huge current going from the battery +ve to the starter is also coming back via the engine block ground cable to the battery -ve. So you really can't replace that with thin cable.

 

goodnigh

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Sorry, have to butt in here. Any electrical system whether AC or DC has to make a 'circuit' - that's why it's called that.

When you crank the engine, that exact same huge current going from the battery +ve to the starter is also coming back via the engine block ground cable to the battery -ve. So you really can't replace that with thin cable.
+1 on that! Bought a set of Concours correct battery cables as

described in a previous post and red and black are identical in

gauge. You would have to assume the engineers that designed the car

knew what they were doing. My battery ground cable goes from the

battery to a point below the battery where the body is welded to the

frame and then to the front of the engine block.

mike

'71 M-code Grande with toploader

 

mach1chick

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In my early years building cars (a Mopar), I couldn't figure out why the car wouldn't even crank. Then discovered the ground strap from the block to the firewall was broken. Yep, ya gotta have that!

 

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