When an engine is designed, the engineers calculate the precise dimensions of every component to result in a motor that will perform as planned in terms of horsepower and torque produced, balance, reliability and efficiency etc. This would be their ideal motorÖ.. but this is the real world where parts have to be manufactured cheaply, and engines are thrown together by human or robotic hands on an assembly line. The Ďbean countersí and the engineers are in conflict here. The bean counters want to use every part made to make motors at the lowest cost. They certainly donít want to pay for extra machining time to bring deviant parts into line. The engineer on the other hand would like any part that doesnít make his precise specifications to be thrown out and not impair the function of the engine. The compromise is the factory motor; parts whose sizes lay within a certain tolerated range are accepted as good. It doesnít matter if many of the parts for a motor are close to the rejection limit: as long as they are within the range, theyíll be used. Sometimes if you are lucky, the errors will partly cancel themselves out if a piston thatís a little on the large side ends up in a bore thatís a little on the big side too; but on many occasions the errors stack up so a smaller piston will end up in a big bore, a big journal may get a smaller bearing (resulting in an over tight fit) or vice versa. So on occasion even though all the individual parts are within specifications the resulting motor can perform relatively poorly. Factors like these are responsible for a wide range in the performance levels of supposedly identical cars straight from the factory. In one study carried out 20 years ago, 80% of Camaros performed approximately as advertised, 15% were significantly slower than claimed and 5% performed better than the published specifications. These variations donít frequently concern the manufacturer or the buyer as most buyers never put their vehicles to track testing or push the redline of their engines. When an engine is blueprinted all parts are brought to an extreme level of precision, parts that donít make these precise demands are either machined to specifications or to match the appropriate part or discarded. Camshafts are degreed to give the valve timing intended by the camshaft designer, not the hit or miss timing that results from machining inaccuracies. If all those Camaros were blueprinted they would all have performed better than the factory claimed performance values and their performances would have fallen within a much tighter range. Furthermore, those engines would have been better able to tolerate sustained operation at the high end of their intended RPM range. In essence, 'blueprinting' an engine is the precise adherence to the designing engineer's blueprints. So why donít the factories do this? Why donít engine remanufacturers do this? Why donít most volume engine rebuilders do this? The answer is simple it costs too much because it takes a lot of time by a skilled engine builder to correctly accomplish, and such precision isnít needed in a production car. Why do car enthusiasts want it? Because they crave bullet-proof performance and proven power over low reliability coupled with hit or miss performance.
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