how can i tell if my timing chain is going bad in my "79" chevy suburban ?

Answer 1

There is s pretty simple way to tell, but it is something that is somewhat subjective in results.
Remove the distributor cap so that the rotor is visible.
With a socket and long-handles ratchet or flex handle, rotate the engine in the direction of normal rotation and watch the rotor. When you see it move, stop. MARK the balancer so that you can see the mark as compared to a stationary item, such as the timing pointer, or something like it. Now, reverse the direction of your rotation, SLOWLY and observe the rotor. When you JUST see the beginning of movement in the rotor, stop and mark the balancer adjacent to the same marker as before.
If there is more than about 10° - 13° between the marks, it is likely that the chain is loose enough to warrant replacement in the not-too-distant future.

Good Luck

Answer 2

You should take it to a mechanic to look at the timing belt, if you fail to see something that is going wrong and don't do anything it might cause the engine to seize.
Usually belts crack and get hard when they go bad but not all belts are the same.
You can check the timing with a timing light to see if timing is wrong, but if you thing the timing belt is getting ready to break you shouold have it replaced by a qualified mechanic.