earth cable

[NO NAME]

i am looking at putting two earth cables, i have a black head and the battery is in the back, i was going to run one from the head to the firewall and one from a engine mount to the subframe but before i drill any holes i thought i might ask were everyone else runs cables for ideas.

[oldjohnno]

Provided you have a good connection from the block to the frame there should be no need for an additional link from the head. Remember that the starter can potentially draw hundreds of amps, so size all your cables accordingly. This includes cables from a starter attaching bolt or block to the frame, the battery neg. to the frame, and the starter solenoid positive terminal back to the batteries. I used to have a big-block powered GTO with rear mounted batteries,  and used heavy gauge welding lead to run from the batteries from the starter, but even with this there was a measurable voltage drop when cranking the engine. To check for voltage drop connect the positive lead of your multimeter to the positive battery terminal and the other lead to the positive starter solenoid terminal (you'll probably have to extend your meter's leads). Crank over the engine and the meter will give a direct reading of the voltage drop. You could do the same on the other side by connecting the meter leads to the negative battery terminal and the engine block to check for voltage drop through the earth leads and frame while cranking..