Hot Rods Battery in the trunk

I know there have been several threads about this but I did not get my question answered. All everyone wants to do is argue about current and how long they have been wiring up cars. Tech tips in old-school rods number 71 states I can hook up the negative battery cable to the starter . I'm now grounded to the frame the tech guide says I'm losing 40 percent of the battery cranking amps. I just bought 1/0 ground wire and want to try this.

 

Mine is. Engine and body well grounded to the frame.

 

The frame (metal) is not the best ground. Much better to run battery ground to the engine block first, then from the block to the frame and body with smaller gauge wire or cable.

 

travisn706: What is wrong with running a ground cable to the starter from the battery???
Or did I misunderstand your post? If you ground your starter to the body, ground your engine to the body and ground your battery to the body/frame and run your 1/0 cable to the starter you are good to go, unless you have a rust bucket.

 

OK, I give you my permission to go ahead and try it, since you already have the cable. What exactly was your question?

 

Steel has about five times the resisitivity of copper. So...if the cross sectional area of the frame is more than 5 times the cross sectional area of the copper wire, then the frame is actually a better conductor than the copper wire.

As mentioned, if you have problems with corrosion at the connections, then you might be better off running the negative wire. But you probably want to connect it to the engine block near the starter, since adding a wire connector at the starter mounting bolt is a bit flaky, and is never done by car makers.

I keep the battery up front where it belongs on my rides, but that's just me.

 

I agree with Rick. I run BOTH cables to the starter body, the positive to the stud and the negative to a mounting bolt. That way I have good current right to the starter. Then I run a strap from the bellhousing bolt to the frame for the lights and all the other accessories, so they have a good ground.

Don

 

Most wiring guides recommend a ground from the negative post on the battery to the engine block. Also from the block to the chassis and to the body. Most electrical issues are usually ground related, you can never have enough grounds. As V8 Bob states the steel frame is not the best conductor. The 1/0 wire should be fine and ground straps are available at auto supply places. Also be sure the paint is sanded from the connection points. Some people have used "star" washers under the connections to dig into the metal but I have never used this method.

 

I think a voltage drop test from bat negative terminal ( not the clamp, for the first test ) to the starter body while cranking would answer my questions if that circuit is adequate and adequately maintained. If the voltage drop was over 0.2 volts DC or so I'd start checking voltage drop piece by piece to see where the problem lies.
http://repairguide.autozone.com/zne...0c152/80/25/fe/59/medium/0900c1528025fe59.gif

More than once such a test has provided pin point answers about what was wrong, and what was right.
That sure beats part$-$wappin' in my book.

Some of the Things that can be positively identified by voltage drop tests before going to the parts store or opening the tool box (except to get out the multimeter) -
Dirty or loose battery cable connections.
Bad or undersize battery cables.
Blown fuses or fuses with bad connections.
Bad switches
Broken wires
Wires that are undersized for any electrical accessory, or wires with broken strands.
Battery with too low a charge

 

I've done it both ways and have never had a problem either way. In fact, last week I was replacing the alternator on the missus' car and had to unhook the battery on her late model...a Chrysler 300. It's a unibody car and the battery is located in the trunk with the ground cable attached to the body shell in the trunk.
I always weld an un-plated 3/8ths bolt to the frame for my ground and use plenty of never-seize on the connection. I now consider it a waste of good [expensive] battery cable to run the ground cable all the way up front to the starter.
The problem I've run into with drilling a hole in the frame for a bolt and nut to attach the ground cable is this:: that connection will experience electrolysis. It will be even worse if a plated bolt is used because of contact with dissimilar metals.............
I experienced this while working as a mechanic for the local municipality......I had to keep those old snow plows running. More than once I was called out on a service call for plows that lost all electrical power while plowing at night out on the street. Sometimes the problem would be nasty connections at the battery but more often than not the ground connection at the frame rail would be corroded...We use a lot of salt on the streets in the winter at that accelerates any corrosion/rust problems.....9 times out of 10 the ground connection would simply be a nut and bolt connecting the ground cable to the frame rail....
BTW, you can also experience electrolysis at the connection if bolting the ground cable to the starter ...especially if the starter has an aluminum end plate.
Gotta clean every part of the connection [frame or starter bolt] and use grease or never seize and clean that connection on a regular basis.

 

Thanks everyone, Rocky lived in Bellevue for 12 years.

 

Bat. in trunk. Had to run a (-)cable to the starter, as the V would drop, (ground was thru frame)
and had poor/or No ignition. Car was reluctant to start for months.
Suppose I had designed in a ballast resistor!
Took some time to deduce this one.

 

Not sure what the question is. If I was putting the battery in the trunk it would be in a box like a motorboat vented outside. Ground cable bolted to the frame or unibody, engine block grounded to the frame or unibody with the same size cable, and a power cable to the starter one size bigger than stock.

 

My 1939 Ford with SBC has had the battery in the trunk behind spare since I bought it in 1972. Always worked as hooked up, even in Illinois winters. Car been in storage 36 years. We are finally getting it going again. New radiator, starter, battery, cables, hoses, etc. Rebuilt dist and 2-barrel carb. Cleaned fuel tank. Will replace electric fuel pump. No room for mechanical. Plan to use a small can at first for fuel. Engine does spin over.

The old battery set up was a hot cable battery thru the trunk floor to starter plus side. Ground is a short cable only to a bolt on the trunk floor. Always worked this way.
Now does not crank enough to start. Swapped starters. Still slow cranking. We're guessing hot cable may be corroded inside and other connections corroded.
Here is the problem. Son picked up 18' of 0-2 copper cable. That's all any parts stores had. He plans to replace the old hot cable along frame to starter from new battery. He plans to add a new ground with the 0-2 thru trunk and to tailshaft of tranny. Will also use the old short ground at trunk floor or replace it with new.
Step two we will add grounds from starter to frame and starter to firewall on the 39 Ford coupe.
Now I'm thinkig this 0-2 cable is too small. Haven't had time to do any of this yet.
So I'm asking the question Travis has asked. We don't care about ohms, watts, volts, electrolysis, etc. Will it work with 0-2 copper cable?

 

Model TI, just to clarify are you talking 2/0 wire or number 2 wire. The reason I ask is that 2/0 is bigger than 1/0 wire. If It worked with 1/0 it will work with 2/0. If your car has sat for 36 years I would suspect corrosion under all your connections. I would take a wire brush to all the mounting points and reconnect everything and use dielectric grease under all the connections. 36 years is a long time for electrical connections to remain dormant, including switches etc.

 

Ground body, engine, and frame!

 

On my Hot rods I always run i-o welding cable pos and neg And as everyone agrees More grounds make happy electric circuits. Don in Water logged n w Indiana

 

Battery in trunk, Negative to frame not body but frame. Number 4 wire from frame to engine block. Positive Number 4 wire to starter solenoid. Number 4 wire from solenoid to starter. Number 10 wire from positive terminal on starter solenoid to inside body for all the stuff. Been that way for 40 years and works well.

 

i agree. good advice. The larger the cable (physically) and the more strands the better.

 

Ill add my 2 cents if it helps, I put the battery in my 68 442 ragtop in the trunk a few months ago. I grounded the block on both sides avoiding the aluminum heads to avoid any chance of electrolysis. I used a Moroso battery box to mount, protect and vent the battery. I used 2 gauge welding cable to run the ground to the rear bumper bracket. I wired the 2 gauge positive through a remote disconnect switch (NHRA required for battery in trunk) and then to a ford style starter solenoid also mounted in the trunk. I wired a 4 gauge cable from the solenoid to the starter that is hot only at starting and dead once the car is running to eliminate any chance of a 12 volt, un-fused, Chernobyl style meltdown (or draw). Then I installed a one wire alternator and ran a that 8 gauge through a 150 amp circuit breaker that takes the entire electrical system off line when it blows and ran that back to the battery. It is safe, it is sanitary and it works perfectly.

I will wire my 34 roadster exactly the same way. It sounds like over-kill but the Olds is a 12.5:1 Joe Mondello 455 that runs hot. Prior to this maneuver I went through multiple batteries, alts and regs and a couple of roll-back tows.

Since this re-engineering I have no dead batteries, no "hot start" cranking, no voltage regulator issues (no voltage regulator) and many happy .250 miles of cruising.
That's how I roll. I hope it helps.

 

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If it used to work fine, Doing a few voltage drop tests will quickly show what cables (if any) and connections need work.
Don't be scared. It's really pretty easy.

 

Just another 2cent answer
My 66 Fastback has had the Batt in the trunk sense 1966.
Grd. In trunk with 2ga. weld cable. 2ga. + to stock start relay
Never has caused 4 family members any trouble. I'll eventually put a Cat disconnect on the ground, no tunes or accessories so it doesn't need any parked power.
On my 06 Mustang the first thing I did was mount the batt in the trunk. But I took a different route and ran both cables up with 2ga. Weld cable to the stock batt location. Used remote batt post turned down to accept stock Ford batt cables and mounted them to an aluminum bracket. Worked great .
The other race car has the batt mounted on the right frame rail, grd. at frame next to bell housing and engine to same.
Every thing hot has to go to a 4 post disconect. Runs a light weight lithium batt and so far I really like it. Sat almost 8 months and fired up first try with no charge or boost.
I don't know it it matters but I like the shortest ground possible on everything. I'm no auto electrical guru but a friend is. I'll have to ask.

 

Welding supply store is best place to buy cables for use as battery cables, auto supply stores don't carry cables that are as good as weld cable, which can be bought in any length you desire.

 

too much initial timing will act like a bad starter, wiring problem......

 

I hate stealing Travisn's thread but we both have the same questions. Been too hot here and too busy. But here's a little battery in the trunk update. The 18' cable my son picked up is 2-0 which is apparently larger than 1-0. He calls it 2/0. The scary part is it's small strand copper incased in a clear cover. Reminds me of stereo wire but the auto parts store called it their largest battery cable. Son bought the 18' piece because that was all they had and likes spending my money.
Later I can cover it with red or black convoluted split plastic loom.
Also now we can run the same wire as a ground to tranny or engine with some left over. I'm thinking a lot of small strands is better than less large strands but I'm no electrician.
Also pretty sure the old smaller gauge hot wire is no longer any good after all these years. It was getting hot when cranking. The new isn't but still the 18' is too long to spin starter enough to start. Plus we haven't changed the ground and added more yet.
The old hot wire has cracked insulation and wherever we've looked it's corroded and powdery. Not a good sign.
So for us we've mostly figured out why the little mouse won't wake up! We'd gotten it figured out but it's more fun to ask questions.
Fighting against us, used a new starter with the old SBC nose, rebuilt the 2-barrel carb, redid dist., new plugs, wires, and other little things. Electric fuel pump is most likely corroded from sitting. All of these things need adjusted and played with. If you think this old car wore out in the past 36 years you should see me!
Thanks to everyone who posted.

 

I worked on heavy duty over the road tractors for quite some time. Batteries were mounted where they would fit, sometimes quite a distance away. The common process was to use a 1/2 inch weld stud on the frame rail for a ground with good stout cables. Star washers were used to bite into the metal, and of coarse braided grounds of equal size were used from the engine to the frame, and body to the frame. I can't believe anything would require more current or cranking amperage than those big old diesels.
Also, I just picked up some number 4 welding wire at Menards, happened to see it in their sale paper a few weeks back, good heavy insulation and available both red and black.

 

I just picked up some number 4 welding wire at Menards
I'm still confused. On regular wire the smaller wire has a big number. So like 8 gauge is good for an alternator and 18 for gauges.
What confuses me is which battery or welding cable is larger? Is 2/0 bigger than 4/0? I just learned 2/0 is larger than 1/0.

 

Ditto on the confusion!

Pat

 

In increasing size...

6, 4, 2, 0, 00, 000, 0000

2/0 means 00
4/0 means 0000

 

I put the battery in the trunk of my '79 Mustang when I put the 351W in it. I ran the live cable through the console to a hole in the floor above the starter and the ground went to the tailstock of the toploader 4-speed. Worked great for a year or so, then I got to frolicking with a chubby chick in the back seat and the seat frame wore through the insulation on the cable and set the seat and carpet on fire....Hot date or what!!??! After that experience I put a Ford starter relay in the trunk so the big cable was "hot" only when the starter was engaged. The battery was in a marine battery box, and there was enough room in it for the relay too. The box was sealed and vented outside, believe me, you WILL smell the fumes inside the car without a good vent. Also anything in the trunk will pick up the stink and even corrode over time.