do timing chains go bad?
 

if so, what are the symptoms? my 93 silverado 250,000 miles might have an issue with the timing. today it was making this weird loping sound like a diesel engine when i was sitting at a stop light. i noticed it because it was echoing off the cars around me.

Timing chains can stretch. Can possibly make the motor jump time.

yes they can.
a very common thing on Toyotas

how do i gain access to the timing chain? its a 350 engine...

easiest thing to do is get a repair manual and do some troubleshooting to make sure it's not something else like distributor timing, bad plugs, wires filters. repair manual will guide you thru most repairs and part replacement as well.

the sound is only there when I put it in drive and idle or when its in drive and its just sitting but its alot quieter than when idling. Its not as loud as before though... u can barely notice it but its still there. When I am in park, the engine sounds normal and the sound isnt there. Could the distributer timing slipped? I know 2 weeks ago I went mudding and off roading and did quite a bit of bumping but it didnt do this then. Then 2 days in a row about 4 days ago I went through a mild trail with some bumps but not anything big. This just started up about 3 days ago.