Know Your Battery Cable Sizes...
The biggest complaint that I hear from antique vehicle owners is " my antique vehicle will not start when its hot." This is one of the easiest thing to fix and involves one simple rule and a little common sense, so pay attention here!
First is the rule. The larger in physical diameter that your battery cable is... the more volume of current the battery cable will deliver from the battery to the starter with less electrical friction (resistance). In contrast the smaller in diameter that your battery cable is... the smaller the amount of current it will deliver to the starter from the battery, and the greater the electrical friction (resistance) will be.
My typical analogy is the difference between a fire hose and a garden hose. The water pressure (which is equal to the voltage) is the same on both hoses, but it is the extra volume of water carried by the fire hose that will put out the fire.
We know that the starter on your antique vehicle should not draw more than 150 amps when cranking over the engine. Your battery is at least 400 cranking amps even if you have the cheap one from Walmart, and if you buy the Optima from Fifth Avenue (with the 3 year free replacement warranty) you will have a thousand cranking amps!
So if your engine does not crank over when it is warm the problem is the current from the battery is not getting delivered to the starter...and what has that job...?
THE BATTERY CABLES !!
The next most important detail is the ground. If your battery ground cable is connected to the painted frame, greasy engine block, rusty water pump housing, or the painted firewall... how do you suppose the ground current will get back to the battery? You are expecting the current to travel through rubber motor mounts, paint, grease, and what ever else is blocking the path back to the battery. You can easily loose thirty percent of your starters cranking power from a bad ground path.
So..what you need to do... is replace both of your stock battery cables with one gauge cables (which is about cuban cigar size) and make the ground cable long enough so it goes directly from the battery to a starter mounting bolt or as close to the starter as you can get it. You want to be sure and clean off any paint or grease at the starter where the starter cable is bolted to the starter, because you want a clean metal to metal contact!
What you are doing is creating a direct electrical path between the starter and the battery so the current can't get lost between the battery and the starter.
I always put a toothed star washer under the bolt head at the starter ground to be sure there is a good solid battery ground cable connection.
Both Battery cables should be one gauge or larger.
OEM 6-volt battery cables were typically 4 gauge, and 12-volt battery cables were/are typically 6 gauge. In the lesson you learned at the beginning of this article I said bigger is better. You ALWAYS want use one gauge cables for BOTH the positive and the ground battery cables, and if it is a heavy electrical load application like an antique fire truck... I use 1/0 battery cables which are the same size as welding cables.
This is true for all 12-volt applications as well. Think about the electrical load of a firetruck with lights and sirens. Many fire trucks (even the newer 12-volt applications) will have dual batteries which means many more cranking amps available. In order to take advantage of that extra cranking power you need the 1/0 cables on hand to deliver the larger volume of current from the battery!
This is also true for drag race cars. How many drag cars have you seen with dual batteries in the trunk and the ground of both batteries is bolted to the floor of the trunk. That ground current from the trunk floor will need to travel to the starter then back to the battery. How is that supposed to happen with rubber body mounts, rubber engine mounts, paint, grease, and related blocking the current flow. Have the trunk floor undercoated or sprayed with trunk splatter does not help either.
We know that electricity is lazy and will take the path of least resistance so odds are about half or less of the cranking power from the two batteries in that drag car will actually get delivered to the starter which is why the car owner put two batteries in the trunk. Having a high performance motor only add to the starter's electrical load. Even with two batteries his car barely starts and the owner always wonders why?
Again...the simple way to look at this is you know that the starter should not draw more than 200 amps in a high performance engine application., You also know that a modern 12-volt battery will be at least 600 cranking amps. So two batteries results in 1200 cranking amps or more which is six times what your starter needs to crank over the engine. The weak link between those two batteries and the starter is the battery cables. You need one battery and a firehose instead of two batteries and a garden hose.
If that same car owner would run two one gauge cables to the front of the car and ground the battery ground to a starter mounting bolt he could eliminate one battery and the car would start way better than using the two batteries he has now.
It is common on high performance applications to have car owners treat the symptoms instead of fixing the problem. The problem is easy enough to identify....the engine is cranking slow because the current stored in the battery is NOT getting delivered to the starter! Most drag car owners will put a battery with 800 to a thousand cranking amps in their car with good intentions. With the wrong size battery cables and the poor battery to starter ground, that car owner cannot take advantage of his high performance battery.
The money making fix (for the aftermarket) is to sell the car owner a high torque or gear reduction starter for a couple hundred dollars, and or a high dollar electronic ignition setup for hotter spark, or a host of other goodies to fix the problem when in reality all that needs to happen is to install the correct size of battery cables.
The focus should be on fixing the problem NOT treating the symptoms. When the car owner figures that out his car will start better than it ever has... and his wallet will be a little fatter, because he did not buy the parts to treat the symptoms, which often times does not fix the problem.
This is true for all 12-volt applications as well. Think about the electrical load of a firetruck with lights and sirens. Many fire trucks (even the newer 12-volt applications) will have dual batteries which means many more cranking amps available. In order to take advantage of that extra cranking power you need the 1/0 cables on hand to deliver the larger volume of current from the battery!
This is also true for drag race cars. How many drag cars have you seen with dual batteries in the trunk and the ground of both batteries is bolted to the floor of the trunk. That ground current from the trunk floor will need to travel to the starter then back to the battery. How is that supposed to happen with rubber body mounts, rubber engine mounts, paint, grease, and related blocking the current flow. Have the trunk floor undercoated or sprayed with trunk splatter does not help either.
We know that electricity is lazy and will take the path of least resistance so odds are about half or less of the cranking power from the two batteries in that drag car will actually get delivered to the starter which is why the car owner put two batteries in the trunk. Having a high performance motor only add to the starter's electrical load. Even with two batteries his car barely starts and the owner always wonders why?
Again...the simple way to look at this is you know that the starter should not draw more than 200 amps in a high performance engine application., You also know that a modern 12-volt battery will be at least 600 cranking amps. So two batteries results in 1200 cranking amps or more which is six times what your starter needs to crank over the engine. The weak link between those two batteries and the starter is the battery cables. You need one battery and a firehose instead of two batteries and a garden hose.
If that same car owner would run two one gauge cables to the front of the car and ground the battery ground to a starter mounting bolt he could eliminate one battery and the car would start way better than using the two batteries he has now.
It is common on high performance applications to have car owners treat the symptoms instead of fixing the problem. The problem is easy enough to identify....the engine is cranking slow because the current stored in the battery is NOT getting delivered to the starter! Most drag car owners will put a battery with 800 to a thousand cranking amps in their car with good intentions. With the wrong size battery cables and the poor battery to starter ground, that car owner cannot take advantage of his high performance battery.
The money making fix (for the aftermarket) is to sell the car owner a high torque or gear reduction starter for a couple hundred dollars, and or a high dollar electronic ignition setup for hotter spark, or a host of other goodies to fix the problem when in reality all that needs to happen is to install the correct size of battery cables.
The focus should be on fixing the problem NOT treating the symptoms. When the car owner figures that out his car will start better than it ever has... and his wallet will be a little fatter, because he did not buy the parts to treat the symptoms, which often times does not fix the problem.
Here are examples of the diameter of Battery Cables. Notice the difference in diameter between the 4 gauge the 1 gauge cables. The smaller the number the larger in diameter the battery cable will be.
You can get custom battery cables made at most any full line auto parts store like Carquest or NAPA and they can build them any length with the ends you need to match your application. They can build them in the store while you wait. They do that for diesel truck and off road heavy equipment applications.
If you follow this simple lesson you will fix your hot start problem once and for all. While you are doing the battery cable upgrade it would be a good time to check out your starter to see what the brushes look like inside the starter and the bushings on either end of the armature.
The difference that battery cables and the proper ground makes to your starting will truly amaze you. It is hard to believe something this simple can make that much difference. And remember...you read it hear first!
And if you want to learn even more ways to fix your hot start problems and upgrade the performance of your antique vehicle's electrical system you can order a copy of my latest book entitled "Help My Car Wont Start When It's Hot! It can be found under technical publications in the "Parts" section of the website located at the top of the home page. It will be the best $15.00 you ever spent!
If you follow this simple lesson you will fix your hot start problem once and for all. While you are doing the battery cable upgrade it would be a good time to check out your starter to see what the brushes look like inside the starter and the bushings on either end of the armature.
The difference that battery cables and the proper ground makes to your starting will truly amaze you. It is hard to believe something this simple can make that much difference. And remember...you read it hear first!
And if you want to learn even more ways to fix your hot start problems and upgrade the performance of your antique vehicle's electrical system you can order a copy of my latest book entitled "Help My Car Wont Start When It's Hot! It can be found under technical publications in the "Parts" section of the website located at the top of the home page. It will be the best $15.00 you ever spent!
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