350 Chevy timing problem (I believe)

I have a 350 chevy, 4 bolt main, edelbrook high rise manifold, quadrajet carb, mild cam, was running good, then suddenly it ran BETTER for a short period of time and then when I stopped and turned off the key, it back-fired thru the carb really loud. When I tried to restart the engine, it would only run for a very short time as I turned the key off. Then it wouldn't start at all. I changed the carb, primed it with gas and when I tried to start it, it just back fired again. A little lost here, hoping someone can help

Disconnect primary ignition lead from distributor or coil (which ever is appropriate). Remove number 1 spark plug. Stick your finger in the hole. Have a bud (or girlfriend/wife) bump the key until your finger is "blown off" the hole. This is known as "blowing no.1". That will tell you A) you have compression and B) you're at TDC, no.1. Look at the harmonic balancer and assure the timing mark is near the"zero" pointer. If it is, remove the distributor cap and verify where the rotor is pointing. If it is not (at TDC), stop here and remove the timing cover (not for a beginner) and replace the timing set. If TDC is as it is supposed to be, check the condition of the distributor gear and verify the distributor actually turns when the engine does.

This could get a bit messy... Best of luck. Report back here, please.

Jim

Thanks, Jim! Forgot to mention that I the engine had a timing gear which I found to be too noisy and I replaced it with a timing chain a month or so before this happened. Thought I might have screwed this up in some way but didn't want to tear everything down before looking for another cause. Will let you know the outcome!