1992 Chevy Van repair

You sure you didn't accidentally disconnect something being down there if not do below to determine if its fuel or spark problem

Disconnect a sparkplug wire or 2 and ground it to the engine -have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs,coil's resistances,cap and rotor /distributor pick-up coil, ignition control module, ECM,Ignitor cam and crank sensors- Note: If it doesn't apply disregard it

BTW what valve replacement are you talking about-