Any difference on how much heat a starter can take?

[olddog]

Steel is not the best conductor, especially when high amp is drawn such as a starter. Low current stuff doesn't matter for auto stuff. It's not good to ground the battery to one end of the frame and the engine to the other. That's a long distance to pull that many amps through steel. A really good quality jumper cable from the battery negative to a starter bolt should be a good test to see if it makes a difference.

If you are loosing a volt or so through the conductors (frame), the starter motor will pull more amps to make the power needed to turn the engine, provided the battery will supply it. The higher the amps the hotter the starter gets. Over time the extra heat may be take its tole.

I have noticed people will run plenty heavy wire on the positive and then overload the negative. The negative side doesn't seem to get much thought, but what ever current is flowing on the positive wires there is an equal amount on the negative.

[Gaz64]

Originally Posted by olddog

Steel is not the best conductor, especially when high amp is drawn such as a starter. Low current stuff doesn't matter for auto stuff. It's not good to ground the battery to one end of the frame and the engine to the other. That's a long distance to pull that many amps through steel. A really good quality jumper cable from the battery negative to a starter bolt should be a good test to see if it makes a difference.

Agree.

Originally Posted by olddog

If you are loosing a volt or so through the conductors (frame), the starter motor will pull more amps to make the power needed to turn the engine, provided the battery will supply it. The higher the amps the hotter the starter gets. Over time the extra heat may be take its tole.

Any voltage drop (resistance) in a circuit lowers the current draw. A variable resistor for dash lamp dimming is a example.
A starter motor operating at 10 volts instead of 12 volts is drawing less current, hence lower cranking speed.

Originally Posted by olddog

have noticed people will run plenty heavy wire on the positive and then overload the negative. The negative side doesn't seem to get much thought, but what ever current is flowing on the positive wires there is an equal amount on the negative.

Agree, both cables should be the same size, the bigger the better.
If the battery is in the boot, both cables should go directly to the starter motor, the negative should be engine grounded close to the starter.

[Ron61]

My battery was also in the trunk and I ran heavy cable from there to the front. I also had a gear driven starter built by a local starter shop and in all the years I had my Cobra and with the racing and heat, I never once had the engine so much as drag when I started it. And one of my header was about 6inches from the starter. I did after the first year or so fabricate a polished heat shield that I could put between the header and starter. I don't like the header wrap or blanket type heat shield.

Ron

[olddog]

Originally Posted by Gaz64

Any voltage drop (resistance) in a circuit lowers the current draw. A variable resistor for dash lamp dimming is a example.
A starter motor operating at 10 volts instead of 12 volts is drawing less current, hence lower cranking speed.

Yes, lower voltage gives lower amp with a resistor, however a motor is an inductive load. I was thinking in terms of an AC motor where the hz is proportional to rpm. If you drop the voltage to an AC motor it will pull more current to make the same power, since the rpm and torque load does not change (in a given service). But a starter is a DC motor. So yes I was wrong, but for a different reason. Your correct, but may have missed a point.

With a DC motor (starter), rpm is proportional to voltage and current is proportional to torque. There is a voltage drop from the resistance of the conductors (wires and frame). So the voltage at the motor is lower, resulting in less rpm. Since it will be turning the engine slower it will take a little less torque to spin it slower. In fact, the motor will pull a little less amps. However there are amps flowing into the resistance in the conductors, heating the wires. The total amp draw at the battery will be higher than what the motor pulls. Too many variables that are unknown to say if the amp draw on the battery will go up, down, or a wash. The hotter the wires get the more the resistance and it kind of turns into a snow ball, where more and more power is going into heating the wires and less and less voltage is getting to the starter motor.

If you do not have heavy enough wires or bad connections, this can happen. When the conductors are all good, the numbers become insignificant and none of this matters.

[RICK LAKE]

Caprimanic RS do a simple voltage check when cranking the car at the starter terminal and see what the voltage reading is. IF it's a mini start the voltage should drop more that 1.5 volts. IF the battery is reading 12.0 volts the start if a mini should not go below 10.5 volts max. The motor and trans are mounted on ruber mounts most times and this makes it hard for electriciy to get to the motor from the frame.The easiest thing for you to do is mount 2 ground straps to the block and or bell housing with clean contact points and add another ground off the battery to the chassic of the car if the battery is in the trunk. Need to remove the paint or use star washers to get the best connact. Add a little dye electric grease on the connects. This keeps moisture alway and stops corsion of the contact points. The other question is where is the timing on the motor when you try and start the motor after a hot heat soak. You may need to get a retard for startup the motor hot. Small note if the car is going to sit for a couple of minutes and it's hot, open the hood and let the heat out. Use anything soft to not scratch the paint. This helps alot on hot days and just stopping for gas. Rick L.