A blue-printed engine, on the other hand, is rebuilt by specialists who are well-trained in their field of work. The main difference here is the quality of workmanship and using parts that strictly follow original manufacturer's
specifications. All critical dimensions, clearances, tolerances, tightening torques, settings, assembly procedures, etc. are on specifications. In this way, the completed engine is given the best conditions to perform at its maximum possible output and reliability.
And how does a blue-printed engine compare with a brand new car's engine? The new engine built at the manufacturer's plant is in a way blue-printed since it is produced according to the manufacturer's specifications. However, there is a basic difference in the processes of assembling the engine and the choice of parts used. A factory built engine is put together from off-the-shelf parts that satisfy certain specifications within a range of tolerances.
This simply means that the dimensions and finish of the same parts may not be exactly the same but are within acceptable limits. When the whole engine is put together the running clearances and fit quality may turn out to be excellent or may be at the lowest acceptable level due to a mass production condition known as tolerance stack up.
If the parts used in building the engine happen to be all of the best dimensions and finish, then the engine will be in top form. On the other hand, if most parts are of the least acceptable dimensions, then the engine will be less than ideal. This accounts for the fact that no two cars of the same model from the same factory perform exactly the same. One will be better than the other. You may have also noticed that the maximum power output stated in your car handbook is never achievable. Now you know why!
