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Feeling a bit overwhelmed with the wiring for my build. I am building a 1955 Olds 88 with a 2006 LS2 and 4l65e.
I have an American Autowire classic update kit for the chassis (55 Chevy version) and had the LS2 engine harness redone including ECM mods and basic tune.
All of the wires on both harnesses are clearly marked so I think I should be able to figure most of it out.
I am mounting the battery in the trunk and this is where I can't seem to just find a simple schematic and parts list. There's seems to be many opinions and parts.
I figured an Optima AGM type battery, mounted on the ledge behind the rear seat.
From there, it just seems to get muddy.
Would like a discipline to switch and know I need a bid *** fuse or CB.
Do I run the 1/0 red positive up front to a firewall bulkhead fitting?
Can the battery ground be out back to the frame?
Wish I could find a simple primer or instruction for this with reliable/safe methods and a parts list.
Thanks for any help!
Don't want to just start buying pieces parts......
I would run the red positive cable to the starter, then tap off of that for the power to the fuse box for the rest of the car. Also, if reliability is what you're after, running a ground all the way from the battery to the engine block is a good idea, copper is a way better conductor than a steel frame. I would probably also go 2/0 on the cable since it's going to be so long.
I have my negative cable mounted in the trunk with no problems, but I have real good engine to body grounds as well. For the positive cable I ran the cable along the passenger side floor and out through the firewall through a good grommet to prevent chafing. The positive cable terminates at a Ford style starter solenoid and I have the solenoid on the starter jumpered. My biggest question was how to run the fuel pump wiring. I would have liked to have kept the relay in the trunk to minimize the run of the high amperage wire but my PSI harness had the fuel pump relay up front so I ran the power wire for the fuel pump alongside the positive battery cable. No electrical issues so far.
The other posts give you the basics, the only thing i want to add is 1/0 or 2/0 is excessive overkill. If you use a good quality fine strand wire you will be fine. I use 2 gauge high quality welding wire, and have used it in many applications with very long battery leads, S10 Blazer with battery in floor of rear hatch, Porsche 944 with battery in rear spare tire well. Both applications used battery grounded to frame and engine grounded to frame, with additional ground from engine to firewall and firewall to frame, the last 2 cam be smaller gauge wire. This is the product i recently used http://www.wireandsupply.com/2_AWG_C...p/wc-2g-01.htm
Mark
A stranded wire like Marky522 linked also works well thanks to a nice bend radius. Stiff low strand or solid wire can be hard to work with. I also second the notion of grounding to the frame. Running a long ground wire is overkill. Just make sure you have plenty of good grounds to the frame throughout the car.
Run a dedicated ground wire. Kills me how people use a positive wire big enough to power a small city than expect rusty body panels to carry the same amount of current. Using body panels is living on borrowed time. There are few things worse than trouble shooting electrical gremlins. And guaranteed you will eventually have trouble with the damn grounds so just get rid of them.
Or you could save yourself a ton of weight and trouble and just put a lithium battery next to the engine. 500 cold cranking amps, $300 and only a touch over 4 pounds. You are going to add more weight in wiring with the trunk mounted unit. I wouldn't brave a michigan winter with one in my daily driver, but for a car in Phoenix it should be all you need. Lithium batteries are better in the heat too.
A proper chassis ground has worked since man created the car, but all of a sudden isnt adequate?
When man created the first automobile, mechanical brakes only on the rear were considered adequate, time proved differently. That said, maybe I do overkill some things, but its way less trouble than trying to run down an electrical problem a thousand miles from home. Also, just pop the hood on any LS vehicle and tell me where the ground cable is terminated....
OK, so as I continue to sort through the opinions on the wire size and termination points, I also am seeing that I shouldn't put a fuse on the main positive cable to the starter.
Should I add one on the positive line from the starter or alternator to the fuse panel/bulkhead terminals?
With the battery in the trunk you will have no issues at all using the frame as a ground with a short cable. Just be sure to use a good ground strap from the frame to the motor and you will be trouble free.
My preferred method to ground anything to the frame is welding a stud or bolt head to the frame and using a nut to thread to it. Guaranteed solid connection. Using a bolt through a hole even with a star washer creates a potential for all sorts of things to interfere with the connection. Tapping the frame works, but most frames aren't thick enough to hold threads well.
But I'm like ls1nova71 and I ground to the engine block.
You really need three grounds: The frame and body grounds are for the vehicle electronics, the engine ground is for the starter, sensors and PCM.
In response to the fuel pump wiring: I use the power wire for the fuel pump to power a trunk mounted relay/fuse to power the fuel pump directly off the battery in the trunk. No matter how much voltage drop there may be running from the front of the car to the rear, it will be enough to power the relay.
When man created the first automobile, mechanical brakes only on the rear were considered adequate, time proved differently. That said, maybe I do overkill some things, but its way less trouble than trying to run down an electrical problem a thousand miles from home. Also, just pop the hood on any LS vehicle and tell me where the ground cable is terminated....
Nice job manipulating my words! But your comparison is actually in agreement with me. Brakes have improved since the first car, but alot of vehicles still use the chassis as a ground. As you point out the factory LS vehicles dont need to because they locate the battery next to the engine, most cars now locate the battery elsewhere and utilize the chassis as the ground.
I am all for overkill, but overkill for the sake of overkill is unnecessary, and wasteful. My point is not to beat my chest and claim only my way is correct, but to make sure the OP knows it is overkill.
Regarding the battery cable, its always a good idea for saftey to use a fuse on a long battery cable in case of damage to the wire/an accident etc. you can go many directions- a cheap 200 amp "slow blow" fuse, or a more expensive 200 amp automotive breaker.
Grounding to the chassis has never been adequate. The phrase is planned obsolescence. Cars built back in the 60's and 70's were only designed to last 7-10 years. Automaker considered it a win-win if they could save $10 deleting ground wires and the car became so troublesome that the owner bought a new one after several years.
There is a reason the Japanese took over back in the 70's. They couldn't put carpet in their cars and made the cars out of shrapnel dropped from B29's, but they didn't skimp on things like wiring. My LS Datsun has a single ground wire from the battery negative to the firewall. Everything else has a power and dedicated ground wire. With the exception of old column switches zero electrical issues in 46 years.
Open the hood of a modern car and look at all the weather sealed connectors. See many grounded loads? Cars have gotten so expensive that they go ahead and build them to last. Modern electronics and sensors are a lot more intolerant of floating grounds than a set of points. Plus the amp draws are much higher than the days of 40 amp alternators. What was a bad idea then is even worse today
Anyone who has ever worked on old cars knows what a pain cutting corners on electrical systems can be.
But you know what? Your car, do whatever you are comfortable with.
Grounding to the chassis has never been adequate. The phrase is planned obsolescence. Cars built back in the 60's and 70's were only designed to last 7-10 years. Automaker considered it a win-win if they could save $10 deleting ground wires and the car became so troublesome that the owner bought a new one after several years.
There is a reason the Japanese took over back in the 70's. They couldn't put carpet in their cars and made the cars out of shrapnel dropped from B29's, but they didn't skimp on things like wiring. My LS Datsun has a single ground wire from the battery negative to the firewall. Everything else has a power and dedicated ground wire. With the exception of old column switches zero electrical issues in 46 years.
Open the hood of a modern car and look at all the weather sealed connectors. See many grounded loads? Cars have gotten so expensive that they go ahead and build them to last. Modern electronics and sensors are a lot more intolerant of floating grounds than a set of points. Plus the amp draws are much higher than the days of 40 amp alternators. What was a bad idea then is even worse today
Anyone who has ever worked on old cars knows what a pain cutting corners on electrical systems can be.
But you know what? Your car, do whatever you are comfortable with.
You must not have popped the hood in anything recently. Every water cooled Porsche uses the chasis as a ground, and a cayenne uses a 180amp alternator capable of peaks over 220Amps. I can sit here and list the numerous vehicles i have worked on that use chassis grounds but its easier for me to say i havent seen an application that doesnt unless convenient to do so in my 10 years of professional wrenching on Porsche, with alot of off brand experience. And for you to imply i cut corners on my electrical work is insulting, i am a Gold level Porsche Technician with almost a decade of experience, and excel in electrical diagnosis and repair. The issues that plauged previous generations of cars, especislly Porsche were ground related but not because of this.
Decided to run positive and ground all the way up front. Is it safe to run the two cables though the interior or should get them out under the car in the frame?
Still trying to sort out the fusing thing. I keep reading that the starter will draw more current than available fuses?
I have no problem adding one by the battery just can't get a good feeling it will work without nuisance tripping. Will fuse holder with a 200amp fuse be good for this 1/0 wire?
Just another topic nobody can agree on I guess.
Is the battery terminal type cut-off OK instead of adding another short wire piece to a remote mounted cut-off?
The good ol' "volt drop test" will reveal lots of answers to wiring issues.
I am of the "grounds directly to the engine" school of thot....
Welding cable for the win. When crimped w/ the proper tool, the fine wires tend to make better contact w/ the connector.
I am running a ground from the trunk battery to the block on my build as well. Probably a bit of overkill, but I have already spent way too much of my life chasing down bad grounds on cars, boats, and trailers. I grabbed two 15' lengths of red and black 2/0 welding cable off of fleabay recently for $45 for my project. You're already running one cable down the body, so no big deal with running a second one alongside it while you're in there.
I'm also using a Ford solenoid in the trunk. Again probably overkill, but it was only like $9 on fleabay, plus a couple extra 12ga-ish wires down the body.
Welding cable is awesome. I have no idea why it isn't more common in the automotive world. It's super easy to work with (tight bend radius), and I believe the finer strands actually carry more current compared to the same gauge size with thicker strands.
Last edited by tracetrimble; Mar 10, 2016 at 10:31 AM.
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Wiring basics 
