Your hydrolic lifters may be gummed up inside, whilst the heads off give them a good clean.
Remember to pre fill them before you reinstall them, if not it will rattle off its head till they pump themselves up (this is bad).
Or get a good second hand motor, ensure you do a compressdion test on it before handing over any dollars, also if possible remove the sump and have a look inside, if its coated in thick sludge find another.
EDIT: or rebuild if you have the dollars
Good luck, hope it turns out well.