I bought this 2000 3.8l V6 Automatic Camero.

I have replaced the ignition cylinder, starter, and battery. I've also used a VATS bypass.

When I crank the car, the engine turns about half a cycle, then I get a whizzing sound from the starter. Any ideas on what that could be?

 

sounds like another bad starter. I once R&R 3 starters in one day until a got a good one.
the third one I had the store test before I bought it
I would suggest you remove it and have it tested

 

It could be a bad power or ground, the high draw can overheat the cable or a connector and cause a massive voltage drop. After saying that it is most likely just a defective starter.

 

Could be above suggestions.
I would externally charge battery overnight, then try again.
If same event happens, feel battery cables.
If warm, too small of gauge.
Replace with larger cable size and wire brush both ends.

 

first off make sure its turns over easy with a wrench on the crankshaft, well not to easy. take some spark plugs out to make easier.

 

I can turn it with a wrench without too much effort, however there is one spot where it gets really hard to turn.... Is that normal?

 

should get hard each time a pistion comes up for a compression cycle.

 

I took the starter to AutoZone and they said it was fine.

I pulled the spark plugs and turned it by hand, and some gunk shot out of the engine. I then tried it with the key and the starter stayed on this time and kept turning the engine. After putting the spark plugs back on, it does the same thing again.

I'm almost wondering if the computer is telling the starter to disengage because it thinks the engine is on. Any thoughts?

 

if you had liquid in the cylinders then i would suspect the engine is toast. blown head gasket or cracked head or block will alow coolant in the cylinders. pull plugs again and see if its got more gunk in the cylinders

 

also battery may be getting low, better throw a charger on it.