[bct]

I plan on mounting the battery in my 32 Ford coupe in the trunk. Since the body is fiberglass, I plan on grounding the negative cable to the frame in the rear of the car What gauge cable should I use for the positive connection. It is about eight feet from the battery to the starter. Thanks for your help.

 

[302 Z28]

If I were you, I would not ground the negative cable to the frame. The frame is not that good of a conductor. On my glass 34 I used 1/0 marine grade cable from McMaster Carr. I ran one black and one red through the interior of the car through the floorboard. Attached the black to the engine, the red to the starter. I installed a Ford solenoid in the trunk so the positive cable would only be hot when cranking. McMaster Carr is a great source for all kinds of odds and ends that you need for street rod building.

The McMaster Carr website is www.mcmaster.com the stock number of the cable I ordered is 6948K95, it is high flex availiable in red and black, and is superb cable, you will not find a better cable at this price.

email me and I will send you a copy of my electrical plan.

Vince

 

[julmer]

I don't have any trouble with grounding the battery to the frame but make sure you add a ground strap from the frame to the engine up front. That much steel is an OK conductor but it has to be hooked back to the engine in good fashion. 1/0 is certainly a good choice. I wouldn't plan on anything smaller than 2ga for a long run like that. Larger is good insurance and likely not a whole bunch more expensive. If you go past 1/0 or maybe 2/0, it just gets to big and stiff to work with.

 

[302 Z28]

julmer has a valid point, but running a seperate ground conductor has nothing to do with wiring a glass car, it just performance. Your electrical system will perform better if the ground path offers less resistance than a steel frame. A 1/0 conductor is far superior to a steel frame in that respect. Ground the negative cable on the bell housing of your engine. On a glass car I would not rely on the frame for a ground on any of the cars systems. Install several ground terminal strips, one in the trunk and one under the dash. Run all your ground wires for all systems to these ground terminal strips. Connect the ground terminal strip in the trunk to the negative side of the battery. Connect the under dash grounding strip to the engine. That way if problems develope you just have several locations where your grounds are, compared to several dozen locations when you rely on frame ground. I would however use a ground strap from the engine to the frame, just for grins.

Also pay a vist to the MAD Electrical site and take a look at the article on remote voltage sensing, you cars electrical syatem will be vastly improved.
http://www.madelectrical.com/electricaltech/remotevoltagesensing.shtml

Vince

 

[docvette]

Cables

Doc here imp:

Just about everything said is a good way to set up your battery box/cables...

I can tell you the way Corvette does it on the rear mounted battery models.

They RUN both cables forward to the Starter area, Ground the Black cable at the Starter area on the block, Then from there Daisy chain with a short Jumper From That ground bolt at the starter, to the frame. The Cable is about 1/0 in size. Then run about a 3 or 4 ga Black wire up to the Alternator Mount bolt. They also run Short Ground Cables , about 3 or 4 ga, from the block to the cross-members at the motor mounts.

They also use several Braided Ground straps from the Valve Covers , Manifold around the Distributor area, and lower block area (I assume these are for noise suppression, as they don't/won't carry much current)

They run the Positive side straight forward To the solenoid.

The cables are about 15 to 20 feet along with routing.

Use star & Lock washers on all the grounds, and burnish the paint from the area for a good Electrical bond.

The system Works well on a Car where Ground is at a premium.

As said before also, Another good Idea is to run a "Ground Terminal" Strip, for all your Future grounding needs.

Hope It helps!

Doc imp:

 

[julmer]

A separate ground cable can't hurt but, if you are dealing with a full steel frame, the gains will be of the preceved difference between Monster speaker cable and ordinary 12ga twin lead. Steel is a pretty decent conductor. The single most important thing is the connections. My choice is bolted connections. I usually place an external tooth washer between the lug and the part and use at least gr. 5 hardware so I can pull it up tight. Lugs must be well crimped or soldered or both (crimp before you solder). The good supply of ground straps will minimize any electrical problems with electronics and audio systems. Never assume the previous guy did it right.
I spent a large number of hours on a starter problem once only to discover that the factory-applied lugs were poorly soldered and had corroded to where I only had about a 10ga wire carrying (trying to carry) full starter current. I finally found out why that Olds 455 wouldn't crank.