Starting 1973 Charger 400

[branded]

Would appreciate any ideas on what could be causing starting issue on a 400 engine.  I have put 4 starters, 3 batteries, new coil, new starter relay and still no start.  It turns over slowly like the battery is going out and the positive cable gets hot after about 15-20 seconds of trying.  When it does try to hit once, that's it.  Won't do it again.  I have double grounded everything I can think of and still won't start.  Any ideas!!  Thanks!

[70 sublime]

When was the last time it did run ?

[b5blue]

Grounds! Rig a start switch by pass to test. Look at inside connections of starter wires I had one made bad, it looked fine but was loose inside. 

[70 sublime]

Yes check the fat wire that comes from battery to the starter
I had to put a new one on my car
The wire was all green inside at the end that bolts to the starter

[branded]

It's a new engine rebuild so it hasn't run yet. 

[70 sublime]

try a different or new cable from battery to the starter

[70 sublime]

The way I figured out my battery cable to the starter was bad
I had changed a couple starters also
The red battery cable was still on the starter from the car
So I just bypassed the cable with a booster cable
You might need some help to do it but hold the booster cable against the main stud on the starter and connect the other end to the plus side of the battery then get someone to turn the key to see if it cranks any different