timing belt? opel combo van?

It will depend if valves meet pistons, some you get a way with, most don`t, and I think yours is in the latter category. you could try a new belt on and try turning it over by hand and see if you have compressions. If not then the head will need to come off to determine the damage, either replace damaged parts or source a replacement engine or work out if it is worth repairing and scrap the van

cdc
July 2013