Corsa 2004 engine grabs

When it gets stuck, remove the spark plugs and try to turn it with a wrench. If it still gets stuck, remove the timing belt and turn the camshaft and crankshaft independently. In the Corsa, this can be done because it doesn't interfere with the valves, and you'll know if it's stuck on the camshaft or crankshaft

Hi Miñoca, I'd start by checking the timing belt and then the oil pressure. It's possible the car has been poorly maintained, which could be clogging the filter. Change the oil and filter, and use a medium-grade oil like SAE 10W40. You should also check that the tappets are the correct ones and that they slide smoothly and easily in their housings. Keep in mind that the problem started after the tappets were replaced. Cheers,