It's probably just the ignition timing.
Valve timing wouldn't change without removing the timing belt. Also, you don't have adjustable valves; therefore, nothing could have gone wrong with that messing the valves either.
If you removed the distributor from the engine, there is a good chance that you didn't mesh the gear correctly. As I said before, set the engine to No 1 cylinder TDC and remove the distributor cap. If the rotor is not at the No 1 wire contact, your distributor gear wasn't meshed properly and you need to remove the distributor and remesh the gear.
Once you're sure that it's meshed properly, you can get a timing light and tune the ignition timing. Digital timing-advance lights are a lot easier to use.
Here are the instructions for your car from the AutoZone guide I linked above. After reinstalling the distributor, make sure that the rotor is at the No 1 contact with the No 1 cylinder at TDC.
Before removing the distributor, position No. 1 cylinder at Top Dead Center (TDC) on the compression stroke and align the timing marks.
Disconnect the negative battery cable.
Remove the ignition wire cover, if equipped.
Detach the distributor harness connector.
Remove the distributor cap with all ignition wires still connected. Remove the coil wire, if necessary.
Matchmark the rotor to the distributor housing and the distributor housing to the engine.
Remove the hold-down nut.
Carefully remove the distributor from the engine.
Install a new distributor housing O-ring and lubricate with clean oil.
Position the engine so the No. 1 piston is at Top Dead Center (TDC) of its compression stroke and the mark on the vibration damper is aligned with 0 on the timing indicator.
Align the distributor housing and gear mating marks. Install the distributor in the engine so the slot or groove of the distributor's installation flange aligns with the distributor installation stud in the engine block. Be sure the distributor is fully seated. Inspect alignment of the distributor rotor making sure the rotor is aligned with the position of the No. 1 ignition wire in the distributor cap.
Install the hold-down nut.
Attach the distributor harness connectors.
Install the distributor cap.
Connect the negative battery cable.
Adjust the ignition timing and tighten the hold-down nut to 8 ft. lbs. (11 Nm).