HOW TO: Upgrade your engine ground cable! *pics* - Page 6 - Ford Mustang Forum

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Thanks-worth a try

Apologies in advance if this is a 'double' post. I tried the reply box, wrote a short novel, pressed submit and never saw it again. My 87 5.0 Hatch sat up for almost 3 years. Over the last year I've done a lot to get it back on the road. In a few weeks I went through the fuel system-cleaning, filter etc, cooling system-new radiator, thermostat, water pump, hoses, belt, fan clutch and blade, brakes, shocks and a ton of miscellaneous basic tune-up and 'other'. First it overheated then it wouldn't get warm enough, then the gauge failed and I couldn't tell so I installed an auxilliary gauge until I figured out how to get the in-dash one to work again. I couldn't get it to idle below 2200 at first but a new TPS (set @ 0.98v) and Idle Air fixed that. For the last few months it's been starting well and running strong. I'm adding this here (I hope) because the most recent ailment may be helped by some of the ground issues. I'm not sure the trouble started immediately after, but my last minor change was the ground cable. It looked corroded where the copper cable entered the lead terminal clamp and the clamp itself looked worn and ready to split. I used a big mama "0" gauge cable that was already crimped/terminated for this car. I put the non-battery end back where it had been - the bolt through the front cover behind the P/S pump. The battery end has a pigtail lead of much smaller gauge that attaches to the stud near the coil and relay stuff.
Lotta words to get to this: Recently it does not start immediately as it used to. Maybe only 1 1/2-3 seconds but it seems much longer than before. Sometimes, if I spin the engine maybe twice, release the starter, then hit it again it does start 'immediately'-almost can't hear the starter motor on the 2nd try. It also has developed an unpredictable intermittent hesitation in the throttle response that make it seems as if I'm just learning to use a clutch. Aggravating and hell on the drivetrain when there is a mismatch of engine speed and car speed. The idle now floats a little rather than solid on 900rpm as it was. Should I run another 'big mama' cable from the engine block to the frame and also from the frame back to sheet metal? I think I know the 'ground strap' referred to - it's a flat braid likely stainless steel from the top of the engine to the firewall. There also is a copper looking perforated contact that seems only to contact the hood - likely for static grounding and/or to ensure the 'worklight' functions. I know in electronics there is a distinction between DC ground and Earth Ground and also a problem called Ground Loop that can introduce noise into circuits.
Sorry to be so long-winded and picky. I couldn't get the photos to open either. I just don't want to go to a lot more time, work and expense either to do no good or maybe even cause additional problems. Thanks for listening.

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I moved my battery ground from the timing cover to the head. The threads in the bolt cover ground were severely corroded when I checked them while changing my heads (bad ground path) - that's when I made the cable switch.

Tom Moss
88 GT 5spd Vert 3:73s, stock H pipe with Flowmaster dumped, Crower 15511 cam @ 110 ICL, GT40P heads & 1.7 rockers, Jet-Hot coated MAC P headers, Holley SM2 intake, 70mm TB, and still SD with 19# Explorer injectors.
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any chance you can post the pics again? can't see them

1988 GT 5.0, MAC Fender Well CAI, MSD Ignition, Ron Davis radiator, Ford Racing 3.73 gears, 5 lug conversion, tubular control arms, fuel pressure regulator, Cobra upper and lower intake, high torque starter, full length headers.
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My bat. Is in fact location i have replaced bat. Terminals groungs soildered and heat shrunk all wires still only runs when it wants can get home runs good go 2 leave 20 min later no fire to coil,also replaced ing.switch and module{had it tested ok}can someone help me out
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In for updated pictures.
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WOW GUYS YALL HAVE ME FN EXCITED AS HELL HERE! I posted a problem earlier about my car not even starting no lights no nothing. Cars only been parked 4 days. All I get is the ding from the ignition with the key. As soon as I call for power ie(headlights, brakes motor) the dinging stops and NOTHING happens. I really think this might be my problem. I also have the same problems as well (Dim lights, false gauge reading, lobing idle, long starts)This is my first 5.0 and ive only has it for 3 weeks and have had more problems with this SWEET looking car since I got it. Its been threw many owners but on the way it got a 2,800 paint job, new motor, rack, etc...and now I have to sort out all the BS so I can enjoy it. THANKS GUYS if it wasnt 10 pm and about 30degrees outside I would be in the garage right now running new wires to see if this would fix everything its worth a try!

1996 GT 5-Speed STOCK (for now)
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Why Juan, why?!!!! Post the pics!

1988 GT 5.0, MAC Fender Well CAI, MSD Ignition, Ron Davis radiator, Ford Racing 3.73 gears, 5 lug conversion, tubular control arms, fuel pressure regulator, Cobra upper and lower intake, high torque starter, full length headers.
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You all have to be a little careful here.

First, aluminum is OK to ground to unless it is too thin or not solidly connected to the block. The same is true for steel. The thing you have to watch is corrosion, or electrolysis from dissimilar metals. You have to pick the metals that contact other metals. I like to use a stainless buffering material, like a stainless fender washer, to stop dissimilar metals from interacting.

Sometimes we beg for problems.

When we ground to the heads how do we think the current gets to the starter?? Hmmmm. The head is gasketed on all major contact surfaces to other parts.

The current flows though any bolts connected to the head that also happen to have a path to the block. Now it just happens that locktite is a great insulator. So if all those big head bolts have loctite on them, we might wind up depending on something else like an intake bolt to get to the intake for a ground. But wait, that intake sits on gaskets! So now what? The current has to find a path to the block some other way. Maybe through the rockers and pushrods and through the cam? Maybe some small wire for some sensor? We just don't really know, do we?

This is why the factory grounds with that big battery cable to the block or to something they are **totally sure** will never be insulated from the starter housing. Then they run a smaller ground wire to the chassis from the battery negative post to power everything else, or maybe from the block or alternator bracket to chassis ground. There is a reason for this, and it has to do with tearing up parts and starting nasty things like car fires.

We are far better off and far safer to ground to a bell housing bolt or some other large bolt that is non-critical for torque, never has loctite, and that is connected directly to the starter through non-critical things.

I'm not saying the heads won't work 98% of the time, just that there is a reason the manufacturer almost never does that. (If they are SURE the heads will directly contact the starter housing all the time in all cases they will.)

Also, we really only need the same size battery in the rear as we had in the front so long as we use a large enough cable. The problem is not the current capacity of the cable, but the total resistance of the path. An AWG-4 cable is super for a six foot run, but it starts to get marginal for a trunk mount battery. There are also safety reasons to not use cheap #4 cables.

AWG-4 copper has a resistance of about .00025 ohms per foot. With a 200 amp starter load that means .05 volts per foot. You've lost a volt (about 10% of the available cranking voltage) in the starter to battery hot cable alone in most rear mount batteries, and if you ran dual cables (one for the ground) it would be 2 volts with number 4 wires. It can get worse if the starter is hot, compression high, weather cold, or the timing is advanced.

I use 00 welding cable for my remote batteries. Why? It has 1/3 the resistance of number 4 cable. I can run it three times further with the same drop. It has a tough jacket.

So why does a bigger battery help? The internal resistance of a bigger battery is lower so the battery itself does not sag as much when you load it. If you have a good small battery that works fine up front and it fails to work in the rear, it is not because the starter suddenly needs a bigger battery. It is because you added so much other loss that the system just can't tolerate what the battery voltage is under load any longer. You made up for resistance in the cables you never should have added by removing it from the battery.

As for trunk grounds, be careful! Think about what would happen if the positive battery cable was pinched or the insulation fails. The only thing that limits current is the internal resistance of the battery and the path from the battery to the chassis and back to the short at the hot cable.

The result will at best be a wire fire, and at worse a battery explosion. You should actually use a full negative return cable to the engine block and ONLY ground to the chassis with a fusable link cable that will melt if a hot lead goes short to the chassis.

Now most of us won't do that. Instead we will want to use the chassis as a return to save running a second cable.

Doing that, we now have a problem in that full starter current has to pass through what normally would serve as a fuse link. This is another reason why you should use a BIG positive cable with high temperature insulation!! Then you can use a short number 6 AWG link from the battery to the ground and keep that wire clear of flammible materials. The fusing current in that #6 wire would be about 700 amperes. So it would melt and open the battery from ground before the main feed wire caught fire or started melting through metal.

The resistance in a number 6 wire is .0004 ohms per foot, so at 200 amps it would only drop .08 volts per foot. It would not hurt the system if it was less than two or three feet long.

Finally, be sure the chassis connection is to a fairly wide fairly thick section of chassis that is an integral part of the chassis. Be sure you ground the BLOCK to the frame very well. Think about where the current will go if you do not solidly ground the block to the frame and you DO solidly ground the battery to the frame. The path is likely up the driveshaft, through transmission parts, and into the bellhousing. It might not be good if you run 200 amps of starter current through some of the needle bearings in a transmission.

I know this was long, but I hope it stops a car fire or damage! At least consider it. There is a reason things are the way they are!

(former designer of tachs, ignitions, timing lights, dwell meters, gauges, sensors, regulators, and other things electrical)

89 LX coupe with 363, modified PT 7675 CEA turbo with billet wheel (at moment), Super Glide transmission, street legal with full interior. Runs low mid 5's in the 1/8th, mid 8's in the 1/4 through mufflers on Pro Radial tires
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Ford in their infinite wisdon grounded my main battery cable to the aluminum timing cover with a steel bolt - when I removed the bolt to check the ground due to starter dragging, all but about the last 3 threads had corroded completely away.

Tom Moss
88 GT 5spd Vert 3:73s, stock H pipe with Flowmaster dumped, Crower 15511 cam @ 110 ICL, GT40P heads & 1.7 rockers, Jet-Hot coated MAC P headers, Holley SM2 intake, 70mm TB, and still SD with 19# Explorer injectors.
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New Pics

Just added these pics.

'66 Mustang Coupe: V-code Emberglo, C-code 289, Pony interior, typical go-fast parts, T5, 3.80 gear
'93 LX 5.0 Vert: Soon to be 5.8 vert
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I'm deff. going to have to do this. My car vibrates for some horrible reason and I just can't figure it out.

I actually registered today after lurking around for the longest time to troubleshoot my problem, then I came across this thread.

1989 5.0 Hatch White on Red (Hopefully soon Orange on Black)

Light Mods: Underdrive pulleys, 3g Alt, Electric Fan, Off Road Exhaust, New Poly Bushings all around, and a TKO 600 .... hope to actually get some use outa that one haha
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Well, since it's a ground strap, you really don't have to put shrink tubing on it. Just for cosmetics...
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right on thanks some of the same issues am having now will do and see if this cures my problems thank you

1990 "whitefox" 1990 vert procharged 331 dss stroker custom tune by ASSC many mods to long to list it's a slooow process !
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my battery is relocated too the trunk and my car cranks slow and has ever since i bought it sometimes its really hard too start and i have an MSD starter and an optima red top.where would you recommend i put a ground on mine its by the top of the gas tank right now. and cant connect it too my heads either there aluminum.
any advice is appreciated.
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I know this is an old thread, but it is stuck so I thought I might add some comments that may be useful to someone reading this thread as I am.

1. Aluminum is an excellent conductor, only surpassed by Gold, Copper, and Silver. If you had an Aluminum head and Aluminum didn't conduct electricity then your spark plugs would not be grounded and you have no ignition. Old man sums up the reasons for choosing other grounding spots besides Aluminum, but having grounded heads is crucial if you want the most out of your ignition system.

2. There is a reason that factory fuses and fusible links are in the positive side of the circuit. Fuses/Fusible-Links must always, always, always be between the positive side of the battery and the potential short, as close to the battery (or power distribution) as possible. Every positive wire of smaller size than the wire it is fed from must also have a fuse rated properly to the size of the wire. The reason is because all metal parts that are not isolated in a negative ground system are treated as an extension of the negative terminal of the battery and most systems use several to many ground paths. The main fuse is rated carry the current of the entire system an only serves to protect the main battery cable. Smaller wires will overheat and catch fire long before the main fuse blows and this is why we have a fuse block in our cars.

If you were to connect a battery in the trunk to the block with a main cable and a fusible link to the rear chassis, a short in the positive cable will not blow the fusible link, or if it does, will still cause a fire because there is still a path through the block for the electricity to pass. If you were to ONLY use a rear chassis ground you could protect the circuit on the negative side. Additionally keep in mind that neither of these will not protect you from a short in the alternator power wire if it has been replaced or modified when you relocate a battery to the trunk as the alternator is a power source grounded through its housing. The alternator output must also use a fuse or fusible link as close to the alternator as possible.

3. Heat shrinking is not only for aesthetics, but it keeps moisture out of the electrical system and helps prevent corrosion.

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