I know it is hard to diagnose this kind of problem over the web with all the possible variables but hopefully some the major collective engine brainpower on Team Chevelle can point me in a good direction. I have a 350 SBC running Trick Flow TFS heads, a Mallory Unilight distributor and coil, a Crower hyd cam (225@50, 480 lift)and a 3310 Holly on an RPM+ manifold.

The engine has always run well since it was built several years ago, pulling pretty strongly to a self imposed 5500 RPM redline. It has only been driven a few thousand miles since then. Now suddenly it has developed a serious misfire at around 4500-5000 RPM. The motor pulls pretty normally (although maybe a little weaker than normal) up to that point then suddenly starts misfiring rapidly and popping back through the carburator. Someone I know suggested that the popping back through the carb indicated it might be an exhaust valve problem and it could be a cam lobe flattened or a weak valve spring.

I am not a big expert on this and all I have checked so far are the plugs (looked fine but changed anyway) and the plug wires (also pretty new Taylor wires-used a cheap plug wire tester)with no improvement. Also all the Crane roller rockers seem to be adjusted properly. I have not checked the timing yet. I hate to start changing a lot of things just to see what happens so any advice on troubleshooting would be apprecicated.

check your timing

i had the same problem on my chevelle after i had set the timing and forgot to tighten the distributor hold down. the timing had backed way off, causing the same symptoms you describe.

You mentioned that the rockers were adjusted properly so that rules out a flat lobe. If the lobe had gone flat you would find one or more loose rockers.