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I am having a pretty irritating issue with my 2008 Z06. It would seem the battery was dead and not start or turn over. Just a clicking in the starter as if the solenoid. I had found that if i didn’t shut the car down in Reverse it would keep some of the electronics on and run the battery down. I bought a new battery, i keep a battery maintainer on it and plugged in. I used to have a problem with my big block starters not working and a good smack with a hammer and the brushes or something would break loose and start working. Today it started earlier and as usual later in the day the starter showed signs of dragging and not willing to crank. With the tender on all day and everything else seeming to work I could not get the engine to start and the starter would click as if low battery. Has anyone else experienced issues with the LS7 starters?
 

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A battery can show fully charged but if having weak cell(s) it cannot handle the current load, worse in hot weather
If not having a battery load tester, an auto parts store should have one to test the battery in the car for you

You did not mention if all stock or has headers as that would dump excess heat onto starter and degrade it
 

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I have 6 friends with C6 Z06s. All but one has that sinking feeling like it won't start this time. Mine had weak cranking also until I installed an Optima Group 34 battery and replaced the positive and negative battery cables with 00 gauge welding cable. It still has the starter motor that the factory installed; and oh by the way, the car has LG headers also. The Optima is rated at 1,000 CA and 800 CCA. Those numbers are about 30% higher than the battery GM recommends. That battery fits; but, you have to lengthen the hold down bolts. Also instead of running the positive cable to the fuse box (like OEM), I routed the positive cable to the top of the starter (like in the old days). Then left the OEM cable that connected the starter to the fuse box in place. Where the negative cable goes to ground near the right rear speaker the chassis has a coating. I wire brushed it off. Cold or hot starts, my Z06 spins over like a low compression small block now.
 

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Sorry, I said Group 34. It is actually a Group 34R.
I’ve got the same issue with heat soak labored start. I’ve already replaced the battery with an Odyssey PC1200, and installed a new Powermaster starter that I wrapped w/DEI.
Honestly, I was surprised when it still had the problem after the two upgrades, but obviously there is something else going on.
06VelocityZ06, how tough was it to run new wires from the battery? I don’t have a problem fabricating new 0/1 wires, just wondering what to expect before I start.
Thanks for any advice 👍

edit: btw, I’m wondering if the optima might be better than the odyssey I’ve got? Odyssey website claims 1200 hot start amps.
 

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First disconnect the battery. The rear compartment carpet must come up, at least the passenger side. The trim piece around the pass rear speaker has to come out (the strut has to be disconnected, support the hatch). The rear vertical door trim has to be loosened (you do not need to unbolt the belt, just move the trim to the side). The door sill and passenger kick panel comes out. Unbolt the emergency door release beside the seat and move it out of the way. Pull the toe board back to expose the BCM. Unplug the BCM connectors and remove the BCM. At this point you can trace the OEM battery cables. I was able to remove the old cables and route the new cables w/o removing the pass seat; but, it would be easier with the seat out of the car. The positive cable was 160" long. I don't remember the length of the negative cable. I got the 00 gauge welding cable on-line along with crimp/solder lugs for all 4 ends. I highly recommend both crimping AND soldering the lug ends. For the battery end, I found a clamp that would work with the lugs. In the back, the OEM positive cable was routed along the seam between the floor and wheel well. I routed the positive and negative cables over top of the wheel well. I suspect attaching the positive cable to the top of the starter solenoid instead of the fuse block helped a lot.

The best analogy for electric power circuits is hydraulics. Volts = Pressure. Current = Flow. Think about household water pressure (usually about 40 psi). How much water will flow through a 1" pipe vs a 1/2" pipe? Current is what gives the starter power. Also look closely at how the engine block is grounded to the frame, the frame is the return path for current. All the current that leaves the battery must return to the battery, it is a loop.
 

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Thanks so much for taking the time for your reply. I definitely liked your analogy of volts/amps and water pressure/volume. It reminds me of what I used to tell the newbies on the fire department: a 2 1/2” line @ 60 lb nozzle will knock you on you @$$, but a garden hose at 60 nozzle will be a nice little shower! Lol

Back on topic, I should have mentioned I have a 427 convertible, but the wire run is probably similar. I’d ultimately like to run a 1/0 in addition to the factory wire, but that may not be possible.

How big do you think the factory + wire was that you took out? I’ve read somewhere (corvetteforum?) that it may already be close to 1/0 in size?

I’ll need to do a series of voltage drop tests on my car before I determine the exact cause of high resistance in the system. I’m guessing it’s a poor ground either between the battery/frame or block/frame.
 

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Thanks for your service! I'd say 99.9% probability the cable routing is the same. I agree with the need for voltage drop tests. Also a good idea to go some place like Auto Zone that will look at how low the battery voltage drops when cranking. (It is hard to catch the low point on a multimeter.) They should be able to provide a strip chart showing voltage drop as the engine cranks. (I've used an oscilloscope on a friend's Z06 and saw below 10v.) That then gets back to the pressure / flow analogy - lower pressure & lower flow. You could easily be right about a bad ground. GM electro coats the frame. I've seen C6's that would not start because the fuel pump had a bad ground. I backed the ground wire bolt off a bit, twisted the wire lug back and forth a few times. Then tighten the bolt and - pump runs / car starts.
I'm in NC mountains and car / all info is in Florida. Back home toward the end of the coming week. Happy to provide more info and some photos then. The shop manual talks about cable size in metric terms; but, as I recall it includes conversion to SAE. I just don't remember either number. I remember the cable I used was significantly heavier and larger in diameter. The reason I used welding cable is because instead of 20 or so wires in the cable, it has about 1,000 wires (obviously much finer wire). The cable bends easier and a little known fact - electrons actually travel on the surface of a wire; not through the core. A bundle of 1,000 small wires has a whole lot more surface area (thus less resistance) than a bundle of 20ish bigger wires. Less resistance means more voltage and current at the starter.
 

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I’m thinking I might just begin to upgrade the charging system too while I’m at it. I’ll probably go with a mechman 240 amp alternator, and I’ll need to fabricate a wire that goes directly from the alternator to the fuse block. I’ve read that some folks recommend a 1/0 wire for that, although I think that sounds a bit overkill.

The battery to frame in 1/0 is definitely in the plans, as well as a 1/0 ground wire from block to frame. Finally, I’ll need to give more thought to the positive welding wire in 1/0 going from battery to solenoid. It’s a larger job that I’ll do if necessary, but I may be able to get away with a 1/0 wire between the under hood fuse box positive connection and the solenoid, all depending on the results I get from my voltage drop tests.
 

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I like your plan. I have a friend's '08 Z06 at my shop to solve the weak start. I'll look at the grounds before replacing the cables. If you replace the alternator, an upgrade to the alternator output wire would be a good idea. I know nothing about the Mechman 240; but, ironically was just reading about the Powermaster 245+. I cannot find on their website, just saw the ad in Modern Rodding. More later....
 

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Yep, I would agree an alternator wire upgrade is a good idea, especially since oem brings the wire down to the starter solenoid first, and then up to the fuse block. I have no idea how that made sense to GM, lol they probably saved two cents by doing it that way.

Regarding the wire size, IMO 1/0 is definitely overkill due to the fact that the battery on charge should never draw current anywhere near what the starter does. However, bigger wire can’t hurt either.
 

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I decided on an alternator and went with a mechman 170 amp. I called mechman this morning and they confirmed that this alternator provides higher amperage at idle when compared to the 240 amp, which is huge for me. I also asked what gauge power and ground wires, and was told 2/0 will work fine. A quick check at a welding supply co. that sells wire confirmed that 2/0 is good for 200 amps.
 

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@06VelocityZ06 , do you remember where you bought your 0/1 welding wire and your copper end pieces? I’ve looked online, but still not sure where to buy from.
I’m definitely going to crimp and solder the pieces, I’ll need to find a good crimping pliers and I’ll need to find open ended end pieces so I could solder them.

I bought a 170 amp mechman, and plan on the following regarding wiring:
• a 2/0 hot wire from alt to under hood fuse block.
• a 2/0 ground wire from alt bracket bolt to engine block.
• a 0/1 ground wire from engine block to frame
• a 0/1 ground wire from battery neg. to frame
• a 0/1 hot wire from under hood fuse block to starter solenoid.

As I mentioned in a previous post, I normally don’t like to throw parts at a problem; however, I feel all the above are overall improvements and certainly can’t hurt. The ground wire from alt to block is probably overkill, but I’ve read that corrosion can cause a poor ground from the alt through its bracket. My intent is to run the 2/0 ground wire from an alt bolt to the same bolt on the block that I will run my 1/0 ground wire that leads to the frame. I also intend to make all these new connections redundant with original wiring (if possible).
 

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I like your plan and redundancy is always good. I got my cable at: https://www.amazon.com/EWCS-Gauge-Premium-Flexible-Welding. They have 0 and 00 (also noted as 1/0 and 2/0). The 1/0 has 988 strands and the 2/0 has 1235 strands. The terminal ends are also from Amazon: Fastronix Military Spec Battery Terminal Top Post Kit and includes the copper lug terminals you will need. (The complete link is too long to copy.)

The shop manual says the factory main cable is AWG #1 with a cross sectional area of 40 sqmm. The cable I installed is AWG 2/0 gauge with a cross sectional area of 70 sqmm, nearly twice the cross sectional area.

If you end up replacing the cable from the battery to the under hood fuse block you will need 160" of the expensive stuff.

The first photo is of the installed Optima battery It will fit down through the carpet door, I just had it all apart to install sound deadner. (I can actually talk to my passenger now.). The battery hold down bolts have to be extended about 1". Note the positive cable routing is also different than OEM. The second photo is that main cable going down to the starter instead of the under hood fuse block.

Corrosion is an issue, especially in high current circuits. I use a very light spear of Kopr-Shield (amazon: Thomas & Betts CK CP8TB COMPOUND, also a very long link). It is expensive; but, more than a lifetime supply. It is the same stuff that was used on tail light bulbs back in the days before OEMs figured out to seal the bulbs from moisture.
 

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