[mr48chev]

NEVER ASSUME- TEST

I've been at this for over 50 years and normally it is because one assumes that something is good so they didn't thest it or check it that is where the issue is.

As Dsraven said, take your volt meter and start looking for a voltage drop in the system.

I keep saying grounds because I have gone out and looked at way too many cars with similar issues where the ground side was comprimised. Made a guy cry once because I took my knife out and scraped about five coats of paint away from under where his ground stap was bolted to the block but the car then cranked right over.

I've also see bad connetions in terminal ends. The worse being one that a guy just stuck the cable in the end of the terminal and crimped it but didn't strip the insulation.

i have a real issue with those skinny 4-0 cables you get at the parts house preferring to spend a few more bucks and get the 1-0 heavier cables. Usually they work when the engine is cold but when it and the starter get hot they don't carry enough amps.

I put 1-0 cables and converted my 454 powered flatbed to use a Ford Solenoid and that solved the cranking problems but this isn't a hot start issue that you are dealing with. It is a resistance in the system issue or a bad battery issue. meaning the battery could show proper voltage with a volt meter but has a bad cell or other internal issue. I would have it properly tested and eliminate that part of the equation.