Hi everyone My 82 gmc 1500 with a 350 engine automatic .Something happened I think the timming chain must of skip a notch its hard to start and I had to crank the iddle way way up to keep it running it has no power at all and smoke black and smells gas pretty bad ,I taught I broke a piston but good compression on all 8 between 160 and 180 not bad for a old truck but I still can't get power out of it .When I put it in gear all kinds of weird noises coming out .I have new plugs,wires,rotor,distributor cap and the ignition module and capasitor, it was running very good until it staled and now that problem .My timming is still on the mark if I mouve the distributor it gets worst .Is it possible that something pluged the exaust ?The only thing that I didn't change is the ecm electronic control module could that be the trouble piece .Mabe its time to retired my truck but I like it and it still good I hope.
Thanks in advance for any reply .

I doubt that the timing chain slipped. Make sure you replace the Ignition Control Module:

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If that doesn't solve the problem, set cylinder #1 at TDC and see that the rotor points to the #1 spark plug terminal in the distributor. Afterwards, set timing to specs with a strobe light.

Your cat may have come apart internaly and plugged up the exhaust. You'd have to disconnect prior to the cat to find out, though. Pretty noisey and a pain, but worth it before you trash the truck.