Mercedes sprinter 312 tapping and lack of power problem

[sprint62]

hello there, i have a mercedes sprinter 312 and recenty put a second hand engine in it. I knew the engine was good because i drove the van the best part of 100 mile home after buying it. After the swap, when the van was quite warm and under load around 65 the lifters start to tap quite loud. I have changed the oil and replaced the lifters. I was thinking the oil pump next but not too sure?? Any suggestions? thanks michael


p.s does anybody know what the oil pressures should be on good running engine on idle and 2000 revs. thanks