V6 starting issue

Seeing if anyone can point me in the right direction before I dig into this.
The halfcab isn't on the road yet but when I go to move it, it'll crank for a bit trying to get the gas to the carb. If I stop cranking it the starter won't engage. No solinoid click either. The AMP light dims so there is a load when turning the key to start. It'll do that for a while until it "cools down" and then will crank again. I swapped the ign switch but that wasn't it although I did feel that the 12V wire was quite warm. I checked the battery cables and although they are old and light gauge, I doubt that they are it because it cranks fine originally.
Is it safe to say its the starter or starter solinoid?

 

I'm guessing it's the starter solenoid but you really need to test it to be sure. The first thing I would do would be to put a test light on solenoid terminal with the wire from the ignition switch. When it gets into this mode make sure there is still power to this terminal when you try and start it. If there is still power here it's time to pull the starter. Since you don't hear the click it's probably the solenoid.

Nick

 

I would clean and check connections first, check battery cables
then use a voltmeter to check for proper voltage
then replace solenoid if necc

 

I had similar issues with my '67 vert. I installed a relay in the system and ran 10 and 12 guage wires. That was in April. No problems starting since.