I currently have the 360 out of my 72 F100. Getting a 390 built. I have a few electrical things I want to work on on the truck. Fix rear lights, remove some poorly wired under dash lights, etc. I am wondering if anyone has ever hooked up the battery without an engine in their truck?? I was thinking of bolting main ground to frame. Anything else to consider. Hooking up the battery will allow me to work and test the electricals.

 

First off, I have never done it before, just to be clear. But two thoughts come to my mind.
1. In theory, as long as the electrons can make it back to the battery, no reason it shouldn't work. Make sure you get all the engine grounds to a solid body ground.
2. Electrical stuff is such a PITA, I'm not sure I would want to tackle it until the whole system is back together. It would be a huge disappointment to me to figure out my issues only to have them change once the engine is back in and the ground path is different.
Again, I have no experience. Just pondering.
Good luck.

 

Yes, I did quite a bit of electrical troubleshooting on my truck with the engine ground cable clamped to the frame with a small pair of vise grips while the engine was out.

 

The battery cable ground should be connected to the block. There is a lug beneath the alternator for this purpose,
Do not ground to the frame.. That will weaken starter current.
Make sure that the cab is connected to the block at the intake through the strap.

 

OP says that there's no engine in the truck, so no need for a healthy starter current.
Hence the question about moving the ground cable to a new location. Temporarily...

zimms, you don't even need to use the large cable if you don't want. You can test the other systems with just a 10ga wire from the negative terminal of the battery to the body. Which you should have already if yours is properly wired. The large cable goes to the engine normally of course, but there should always be a separate ground to the body. Many trucks have had this one removed when a PO changed battery cables.
But clamping or bolting the main cable to the frame will not hurt anything. Just make sure that there are sufficient body grounds as already mentioned. One to the fender, and another to the firewall/cab. Since the normal one from the back of the engine will be missing, you can create your own. There's a chance that the cab will be well enough grounded through the fender ground, but it's still better to keep one to the firewall just in case your fender connections are weak from rust and/or paint in between the metal parts.

And I would say an equally important step while setting this up would be to make sure that there are no additional positive wires hanging loose. Such as the original charge wire from the alternator. Normally one end would be at the starter relay/solenoid on the fender, and the other at the alternator. If that wire is still attached to the relay but the alternator end is just hanging out in space waiting for something to short-circuit to, that would be a bad thing.
That's probably the only one I can think of off-hand, but only you can verify first hand what's what and what's not safe to leave in place while checking. We can't know what a PO has added in the past, so it's up to you to hunt down and make safe any positive wires that are not connected to anything at their other end.

Paul

 

Instead of a battery, use a battery charger. They have protection circuits and lower amperage so you can test things without major shorts or fires.

 

Have you used this method? It is my understanding that the battery charger doesn't work if there isn't a battery between the clamps. Just asking.

 

I have, and it can be very finicky. In my case I switched from automatic to manual on an old style not-so-smart charger and it worked some of the time. I finally gave up and just went to the battery.
I wasn't too concerned because I knew I'd done everything I could to make sure that each and every circuit was either connected or protected from shorting to some random metal bit, so confidence was high.
But I cringed and squinted and puckered anyway when I connected that last battery lug!!!!
It was my first full re-wire. Since then I've learned to trust the wiring harness companies to have done a good job on at least 99.9% of their connections and designs. And to trust my eyes when I'm quadruple checking my work.
Where's the fun in that, you might ask? And rightly so, as letting the sparks fly and "letting the smoke out" can be exciting and invigorating. But I make up for the loss of excitement in not having to re-do any of my recent work! Works for me...

I'm guessing different chargers will act different ways, but more and more of the smart charger types are getting even smarter, so who knows. Worth a try I say, because having that extra layer of protection is not a bad thing.

Paul

 

That is NOT my kind of excitement.
Thanks for sharing your experience. I do like that there is the circuit protection in the charger. Save some money on burning up your truck.

 

This is ideal a battery tender is what i have used in the past. I also just use a small rc car battery sometimes when I rewired my mustang. I have a painless harness in my 68 mustang and 68 f100 if I could make a suggestion buy a whole new harness! Life will be so much easier and you will know you have a solid foundation

 

yeah I just re-wired last month using American auto wire and tested each circuit using a Battery Tender. The newer chargers with intelligence probably won’t work.