Do these things:

1) Clean battery terminals with circular wire brush that fits inside the terminals
2) get a NEW battery. Don't laugh. Walmart $110
3) Trace large black wire from the battery- make sure it goes to the frame. Clean the connection.
4) Trace the braided THICK ground wire from the firewall to the driver's side head. Make sure that wire is there.

After all this work, if it still does not go ---
May be the starter is trying to extend the bendix into the fly wheel and the bendix is not extending.
the hummm would be the starter motor running with no load.

the starter may FLY APART as the engine will RPM limit it. Starters are not meant to run with no mechanical load on them.

 

And the starter gear will create a metal "fuzz" that will make the CKP sensor turn off sparks....

And I just pulled my heads, had a neekid ground stud. Love the quality PO work.

Note for the city slickerz - "naked" means you a'int got no clothes on. "Neekid" means you ain't got no clothes on and you're up to sumthin'.

 

I'm ALWAYS "Neekid"!