is one of the first, and best things a hot rodder
or racer can do to a production engine
. Blueprinting an engine is nothing more a rebuild
done to the most precise tolerances possible. That simple act improves reliability
, which is particularly important when you plan to run an engine at the limit
Except for Ferrari, Porsche and a few other of the most expensive, specialty manufacturers, automobile engines are built to fairly loose tolerances. Perfectionism is expensive, it means you have to throw away a lot of useful part and/or spend a lot of extra labor making things just so. Truly precise fits require precise parts Therefore manufacturers use a coding system to delineate the quality of fits. When we installed a new --and stock-- engine in my ITB Toyota for it's last race, the 2TC engine we had was exceptionally nice. Each cylinder had been marked with a number, in this case the code was 3, 3, 4, 3. That indicated the relative sizes of the engine bore, allowing the assembler to choose the correct piston ring size from his pile of pre-sorted pistons. My engine was an exceptionally good motor because all the cyliders but one had the same bore. And we're talking a Toyota motor here, and those are known for precision.
When blueprinting an engine, every part is returned to exactly factory specification using high quality machine tools. Bores are made precise, engine studs are changed for new, everything is made as new. Parts prone to wear, such as the timing chain, oil and water pumps are replaced. The block and heads are cleaned with anal retentive care. Every single part is checked for wear or cracks, and replaced as necessary, often magnafluxed to detect cracks beneath the surface, or too small to be seen. The crankshaft and flywheel are checked for straightness and rebalanced. Align bores are given if need, and the crank is nitrated or given other treatments. The head and block are milled for perfect straightness. A five-angle valve job is done.
Often, a blueprinted
engine is simultaneously balanced
. Balancing takes all reciprocating parts and makes sure they all weigh exactly
the same. This us done by weighing each piston
the other pistons until they all weigh the same as the lightest piston-- or some pre-determined lesser weight. The same is done for the connecting rod
, rocker arms
and all other moving parts.
This reduces engine vibration
s due to imbalances, and reduces reciprocating mass
inside the motor. This permits the engine to rev much higher, reliably
A blueprinted engine is a new engine no matter how many miles it may have been driven. In fact, it's better than stock, because this type of precision is almost never done at the factory. A racer who starts with a blueprint job can trust his motor. Because a blueprint job is so thorough, it's easy and inexpensive to perform a host of other modifications at the same time. Besides balancing, the cylinders can be bored, a stroker crank installed, aftermarket parts like racing cams installed.
Blueprinting is not cheap, costing a couple thousand dollars when you bring in the engine. It takes lots of time. But if you're serious about motorsports, and the rules permit, blueprinting is the first place to begin your engine program.