Oil in the escape

Hello, friends, I want to know why my 6 -cylinders online diesel engine sele oil by the exhaust, it is recently repaired, guidelines of valves and valves were changed but the seats of the valve were not changed, I think that is the problem, if someone can tell me what are the causes of that problem ...
I do not think they are the rings because they were left with the exact olgure and the cylinders were directed and the same were used. pistons ,,,
I thank you to collaborate ..
Thank you ...

Make the mood that the engine must disassemble it again, although you do not indicate how many cylinders are moistened or if they drip through the joints, in any case you must disassemble and check:
quality of the rings that were installed
cleaning of the groove of the pistons and tolerance between slot and ring
tolerance between piston / cylinders and the burnished
spark plug if it corresponds to the engine
. They are loose.
When we rectify an engine we depend only on the rectifier and in many cases, many work on what they suppose, but, we are the mechanics that we have to control that the tolerances delivered are what the manufacturer says.
There is nothing more to repair an engine and have to disarm for that problem.
My advice, lifts the crankcase, disassembles a piston and its oil ring, try it in the cylinder and check if it presses against the cylinder.
I hope you let me know when you have the failure.
Encouragement and encouragement, not ovides warn how it was

Holla Tanvien fixed if Lois Balvula rertenes were chanted and that the Silindro Tapa Board has the right torque if you educated a leakage out there with enough adjustment., If you reach the disarmament of the engine you set that the pistons are not obailed by the abesses wear cannot be seen with the naked eye. I hope you do not get to disarmament luck.

Hello, thank you for the contribution, I think I must simply do it, I hope to have other possibilities. Before assembling it, the slack of the rings both in the piston and in the cylinder and it was perfect, as I doubt I think that the rings stuck to the piston or perhaps it is the joint of the butt because I do not see another, I hope that they continue to collaborate if something escapes me ...
but to disarm it was said.
Thank you ...

You will undoubtedly have to disassemble, but you are sure that it is oil? If you changed everything I did not give a problem unless the fuel was made with the oil, and this may be due to the piston route.