Engine ground

[ChargerST]

Out of curiosity: why is the main connection of the negative battery post to the engine and not directly to the starter motor and the alternator (= isolated ground)? Those are afaik the only two items that need grounding through the block (and some sensors that ground through the block like oil pressure sensor). Not sure if it would help with possible electrolysis damage if there were direct connections to starter and alternator? Battery needs to be grounded to the body as well (usually done through a ground strap from engine to body).

Or is it a good idea to have a direct ground wire to the starter motor in addition to the engine ground?

Edit: Apparently isolated grounds are a thing in boats and cars with sensitive electronics. Advantages are reduced corrosion, less voltage drop, less electrical noise

 

[gkent]

Your spark plugs need a good ground !!

FWIW, my trunk mounted battery grounds to the bracket between the inner fender and dutchman panel. Up front it grounds from the frame to the block.
The efi and MSD get a seperate ground off the battery.

 

[ChargerST]

Correct! No spark without grounds! A separate ground to the starter would still make sense imo as it has the biggest current draw.

 

[gkent]

That would have cost the manufactures MILLIONS for the extra 3 feet of cable !!