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I have a 53 3100, and the truck runs fine it starts up but when it get's hot it acts like the battery is dead but after it cools down it starts right back up. I was told that my cable to the starter is not big enough. It still has the 6 volt system. Can anyone tell me what the cable diameter should be? I did add the ground strap from the engine to the frame and still same problem. Any help is appreciated.

Sometimes thes motors tend to be harder to turn over when they are warm. My 216 is one such case because I shimmed the main bearings with the minimum possible clearance. I would try turning it over by hand when it is cold and then when it is hot.

Another thing to look at is the size of the cables. There are a few posts on that. Also if the timing is too advanced, it can cause problems. You can check for this by turning it over with the ignition off.

You should try what truckernix suggested first. If then you do need to replace the cables then the forum by Randy Rundle under tech tips says the original 6 volt cables had 4ga wires from the battery. You can also do as he suggested and what I would do is use 1ga which is a bigger wire. To better understand it the cables act like pipes in a water system. The bigger the pipes are the more water will flow. The smaller they are the more it will restrict water flow. The water in the case of your truck would be your amps from the battery. I would suggest to replace both the negative and the positive. This will create even current(amps) flow from the battery.

If the truck has 12V cables, like the only ones available in the parts stores, your cables are too small. Lots of 6V users use 00 cables.

That is what I heard they have to be 00.

Yes, 00(2/0) is correct if you use aluminum cables. I aplogize for not making that clear and thanks guys for catching that. My calculations were based on copper wire which witstands higher amp capacity and has better durability then the aluminum. Most likely the stores will carry aluminum. If you do find some that are complete copper then it will be 1AWG. If you are confused then just search N.E.C. table 310.17.

1 AWG copper would probably work fine. I use 00 AWG copper on my 6v vehicles (hot and ground wires from battery).

Installed the 00 cable, it made a big difference in the way it starts, just hit the starter and it fires right up no resistance.

It looks like you had a fun productive weekend.

Good news, Bud.

The order of importance in the starting system (with no wasted $$ spent):

After checking out the battery and all components in the ignition system, if the engine is cranking slowly, check out (or install/service) the following:

1. Good cables from the battery - both the positive lead and the negative lead (1 gauge to 00 gauge, copper).

2. And, clean/shiny contacts for the cable-connections - clean metal, protected with conductive, anti-oxidant grease ( Kopr-Kote, Kopr-Shield (no longer listed by Eastwood), or NAPA: BK 7652569.

Next to consider (although, I now do this first on my trucks):
3. From the battery: run the positive cable to the starter (the normal arrangement) AND the negative cable to a starter-to-clutch-housing bolt (not the normal arrangement). Be sure to still use other frame-to-block ground cables (and maybe a head-to-firewall ground cable).

4. Then, rebuild (or have rebuilt) starter, or buy a new/rebuilt starter (NAPA now has them, as low as $60).

If the above actions still fail, you will have good starting components (that you will need anyway). Unfortunately, you'd have to look elsewhere for the cause of the slow-cranking (too tight an engine?).