An engine rebuilt involves the removal of the engine from the car itself and replacement of the damaged parts after getting disassembled completely. Engine rebuild should not be overhauling of the entire engine. You should go for the engine rebuild, if your engine has worn out bearings and sick seating piston rings. An engine rebuild is absolutely a protected investment that reduces the need for repairs and extends the life of the car engine. So, do engine rebuild when it is needed and do that under the supervision of an experienced car mechanic.