Have a 1968 firebird with a 1970 455 propably doesn’t have 1500 miles on it just had the heads redone again. Because they were messed up. I put the engine back in Had the car running great and took it to a gas station to fill it up with fresh gas 93 octane about 15 minutes away. Then drove home my son wanted to take a ride so I took him out the road and when I turned onto the next road I mashed down on it and it launched then something changed and it started missing so I drove it home it won’t idle now I have checked plugs and wires all firing actually charged plugs I pulled the distributor it looks fine reset it several times and still having the same problem. My father suggested it jumped time but it has a fairly new double roller timing chain anyone have any suggestions?
Sure does sound like an ignition problem. Did you verify the timing didn't move? If it didn't , I would doublecheck everything you already checked. Distributor rotor, points, ignition coil, wires and plugs. Ohm out the wires!
Did you test every plug wire with a timing light to see if they were all firing correctly? Maybe a cross fire from one wire to the next? Bum condenser in the distributor? Cracked distributor cap or carbon track causing a crossfire? Sure it is not a fuel delivery problem?
Sounds like a jumped chain but with that many miles it wouldn't seem likely. If the timing chain skipped a tooth or two, not only would the valve timing be out, but also the ignition timing. The camshaft drives the distributor, if you checked the timing and it was the same as before the problem started it most likely isn't the chain. If you pulled the distributor before you checked the timing that test wont work.
Did you get any backfire or blowing out the carburetor?
Check for vacuum leaks, a jumped chain may have blown a vacuum cap or plug out/off.
If you can get it running check for noise under the front cover.
You could pull the fuel pump and see if there is excessive slack in the chain.
Only real way to know, other than find a cause elsewhere, is to pull the front cover and check the timing marks on the gears.
Don't rule out the fuel system, crap in the carburetor can and will exhibit similar symptoms, I had plugged fuel filter feel just like a dead miss while cruising down the fwy. And being it happened right after you mashed on the fast pedal...well?