1998 Toyota Celica knocking

I have recently replaced the piston rings and cylinder head on this engine due to the previous owner running it with a very thick oil which blocked up the oil return rings and caused all kinds of problems. For about 300 miles its been running beautifully with good performance and fuel economy. Just recently it has developed a definite knock at switch on which dissapears quite quicklt then anything above 3000 revs on acceleration. I was convinced that when I refitted the conrod bottom end connectors to the crank shaft (with new bearing shells) that I put them back on the right way. If I have got one the wrong way around. Would this be the cause?
thanks for your help.