Norbert,

I had about 110,000 miles on mine when I replaced it. But from what I can tell my vette was not driven hard and I am the third owner. Here is what I did to determine that it need replacement. First, if you set your timing at idle, rev the engine up a little, then let off the throttle. If the timing drops below your set point or above it you could have a stretched timing chain. Or if you see the timing moving around while the engine is idling. This does assume your distributor advance is working properly. Another way is to remove your spark plugs and distributor cap. Turn the crank by hand counter clockwise until you see the rotor on the distributor move. Place a mark on the harmonic balancer and now turn the crank clockwise until the rotor starts to move. Measure the degrees the crank moves with no rotor movement. Anything more than 5 deg, you should look into replacing. I had around 10 deg on mine and the chain was pretty sloppy. Some of the master mechanics on here may have a better method or different range on the degrees.

I've changed more than my fair share of timing chains, a lot on small block Chevys. I've never encountered a valve interferance problem. Let us know if you have on yours.

Dave

I have been toying with the idea of more HP for some time now and I guess this will push me towards a decision. I am leaning towards pulling the engine, have a shop freshen the bottom end, new cam, new heads, new intake, new distributor, and new carb and lots more torque and oh yea new timing chain. Now to start the research on part combos, I know there were a handful of posts on the topic. It would be nice to reuse my existing matching numbers engine since I am limited on storage space but maybe it is time for a 383? Time to work up some cost options and beg my wife... again...

I've changed more than my fair share of timing chains, a lot on small block Chevys. I've never encountered a valve interferance problem. Let us know if you have on yours.

Dave

reading this i even start wondering why i doubted about changing my timing chain...(maybe because it has a low mileage if i can believe the papers that came with my car)

anyway.. always a good thing to read about other's experiences or problems

art-corvette