[Bill OH]

I have a 38 Ford 221 that had a ground strap from the battery to the firewall and another ground strap from the firewall to the engine, all of which yielded a voltage drop of 0.35 volts.
Steel does not have the conductivity of copper. I removed the ground strap from the battery to the firewall and replaced it with a 24 inch 1 gauge cable with a copper eye terminal that I soldered on with silver bearing solder. I connected that cable from the battery to the ground strap that goes from the firewall to the engine. Voltage drop now 0.10 volts and the starter spins much faster. I have experienced grabbing the throttle rod on a 47 Ford that was hot - installed a ground cable from the battery to the engine. I might add that the 1 gauge copper cable that I used had a steel eye terminal that caused an additional 0.1 volt drop, hence used the copper eye terminal to remove that drop.