That is EXACTLY what I'm saying, and since you didn't understand it the first time, I'll repeat. If the front section of the car ahead of the firewall has such rust problems THAT IT CANNOT CARRY BATTERY CURRENT enough to ground the block, and allow the starter to crank the engine, you'd better not drive it. Clear enough?
The op mentioned nothing of a structure NOT carrying current, you assumed. If you have troubleshot electrical systems (not electronics on a bench) you would know that the most common faults are at connections. And in this case we don't know the true characteristics of the joints of the car, let me be clear, the car does not have to be falling a part to have bad grounding characteristics, we are not metallurgist who know the characteristics of the frame including the welds.
It's called technical knowledge, and I don't appreciate your "summary." You weren't there, you have no freekin idea what I've worked on
Well everytime something like this comes up you post pictures of an old radar building and say, look I know what I am talking about, sorry that just doesnt do it for me, posting a picture doesn't not justify an incoherent answer.
In this discussion, Ohm's law is all we need. It's been around a very long time and it still works. No guesswork with it, either. The common term is "IR losses."
What are you talking about? You don't have resistance values for his specific car for certain runs so you can't use the formula, period. hell you don't even know what voltage his system runs at, could be running high or low. So how do you impose you use this formula, not only that but why would you use it? are you going to go out to the car with a calculator and punch in numbers, sounds ridiculous. All you need is to check the resistance of bonded objects and personally deem what is ok and isn't, unless you have done a bonding check on his car with a proper meter you just can't assume
What we REALLY don't need here is your sarcasm. Nothing you offered in your post is factual. Nothing.