300 amp X 12 volt Circuit breaker

[Excaliber]

Here's a link to circuit breakers virtually identical to what ERA uses.

http://www.wiringproducts.com/contents/en-us/d60.html

It mounts on the firewall, right next to the starter solenoid. A reasonably heavy wire attaches to the same post on the solenoid that the main battery + cable attaches to. The other end of that "feed" wire goes to one side on the circuit breaker. ALL power to anything (but the starter) passes through this circuit breaker. Add up your worst case scenario for a amp load to the car and choose a circuit breaker that is equal to or greater than that amount (far less than 300).

As you have a Chebby engine your solenoid is likely mounted on the starter. This will require a much longer wire and subseguently a much heavier wire due to the length to reach from the starter + plus battery terminal connection to the newly mounted circuit breaker. Ford really did have a better idea in that regard,,,

It is all but impossible to provide a protection circuit for the starter, any starter. It simply draws to much power, it NEEDS to draw massive power. Enough power to "burn up the starter" if that what it takes.

So what happens if there is a "short" to ground by the battery plus cable? The damage will be limited STRICTLY to the + cable and the battery. No other systems will be damaged (generally speaking). Where and how the + cable makes contact with the "ground" will determine the amount of potential amp draw from the battery. The + cable MAY get "red hot", melt the insulation, discharge the battery to the point of it exploding. The cable will either burn through, or the battery will blow up first. It is highly unlikely you could achieve a strong enough "short" for the cable to carry any significant amperage in the first place.

Such a scenario might be a "wreck", where the battery comes out of it's holding clamps. The + cable may come in contact with the headers which would melt the thick insulation. That could provide a pretty good discharge rate, all though, that may be the least of your problems if your in a wreck that bad.

Let's say the insulation "rubs through" on the body, wears away the insulation. Thats a piss poor connection, it won't draw big amps, less than 50 I'd bet! A 50 amp circuit breaker, for protection against this scenario will not be big enough to run the starter however! You would need a 300 amp for that, which won't keep the car from burning down. A typical "short" will draw far less than 300 amps, but enough to possibly blow up the battery or catch the cable on fire. In such a case the only thing you could say is, "Life sucks sometimes".

[Ronbo]

Had a "mishap" many years ago where I was changing out a solenoid on my Chevelle. After re-mounting the header I failed to notice the battery cable touching the header tube.

All was well until the headers heated up and burned through the insulation. I heard a hissing sound followed by lots of white smoke. After scrambling to get a 5/16 wench to undo the cable, I cranked on the neg side terminal (which was very hot at the time) and the whole thing pulled out of the battery. (melted the casing)

Casualties were the battery and both cables insulation fried off. And of course the obligatory ribbing from my buddies.

I pay better attention now though.

As far as exploding batteries, in the case of lead acid types, over charging and fire are more likely to cause an explosion than rapid discharging (Granted rapid discharging can certainly make other stuff explode / catch fire).

We had a kid that worked at the paging company I was an engineer for who had hydraulics installed on his POS Geo. One night the hydraulic system shorted out and lit the interior off. The batteries then exploded one by one in the resulting inferno. None of them exploded from the short.