OK I am sure there is a thread on this somewhere, but didn't see it. So I am sure someone knows about this with all the issues I have seen posted about this engine.

2008 chevy cobalt lt, No Mods
1. Car died after a rough start at work backed out of spot went about 5 feet then dead like it starved out of gas
2. car would barely turn over after like a dead battery
3. Changed battery just as bad
4. towed it home put battery on charger, Got it to finally try to turn over and nothing
5. Cleaned cam sensor and smelled gas at exhaust but no fire
6. removed crank sensor appears fine cleaned it
7. Removed head found 2 broken rockers cyl 2 and cyl 4.

 

The broken rockers wouldnt cause it not to start, or be slow to crank. I would worry it may have skipped time. You can crank the motor to TDC by hand while putting a screwdriver into the #1 spark plug hole and observing it at its highest point, but dont turn the motor counter clockwise any more then a few degrees if you overshoot TDC. You can verify that the timing marks on the cam sprockets at 10 oclock and 2 oclock position, either now or on the next revolution. If you are looking at the chain, you cant go by the colored links at this time. Rockers can be replaced without removing the cam and carefully loosening the cam bolts evenly until you have enough clearance. Also carefully look for debris from the rockers. They can shed needle bearings everywhere and you must be careful to find everything you can. Once you replace rockers and confirm time do a compression test to make sure the valves didnt contact the piston

 

The rockers probably broke as a result of jumped timing. The rockers would never just break on their own.

OP, id say its probably time for a timing set and a valve job at the very least.

 

OK pulled #1 spark plug (looks like it may have been hit) or just never gapped igniter bent down touching the contact) neither #1 or #2 piston moving as I rotate forward camshaft. Does make a sound as I rotate the shaft like it is skipping teeth below. Looking down from the top end at the chain I can see one down in the bottom about the same size just behind it that never moves. Assume that is connected to the crankshaft also. So what is easiest way to access crankshaft?

 

Sounds like you may have broken the keyway on the crankshaft or your chain really is just that loose. Youll have to pull the front cover off to have a closer look at it. Use an impact gun to get the crank pulley off and the rest should be pretty straight forward.

 

Wait, did you crank it using the camshaft bolt? You should only turn motor by the crank bolt.

You may need to use a harmonic damper puller to remove the crank pulley. Many large auto parts chains will rent those for free ( pay full price to pick up/full refund upon return ). They are supposed to slide right off but any damage to the keyway they get on there pretty tight. The front cover isnt as hard to remove as it would seem. Dont forget the 13mm bolt in the middle of the cover over by the water pump inspection cover.