What does it mean to Blue Print and Balance an Engine?

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Putting an engine together is more than simply bolting parts together. The engine has tolerances and torque requirements. If you are building a street racing engine that is going to be used more aggressively than your mother’s Buick, it’s a good idea to balance all the moving parts. This makes the engine far more efficient and allows it to maximize the horsepower output. All racing engines are balanced and blue printed.

Balancing & Blueprinting is nothing more than machining different engine parts to specific tolerances. The pistons are all machined to weigh the same. The big end of connecting rods and small end of connecting rod are machined to weigh the same (separately). Then the weights of the pistons, big end of connecting rods, small end of connecting rod, one set of rod bearings, one set of rings, one wrist pins and oil weight (usually 6 grams) is recorded and the bob weights are made up from the formula for the type of crankshaft being balanced. Then the bob weights (4 for a V8), dampener, flywheel (flex plate) are bolted to the crankshaft and spun to balance the left side and the right side of the crankshaft. Then spun with the left side and right side coupled together to make sure the crankshaft is still in balance.

The crankshaft is has either welded on counter weights (or heavy metal installed) or drilled on the counter weights (left and right) to bring the crankshaft into balance.

To blueprint an engine consists of several machine shop operations including but not limited to:

  • Bore & hone cylinders (usually w/Deck plates) and honed to the correct clearance.
  • Line bore or line hone the main housing bore in the block. (Or at least check to see if the housing bore is within the correct specifications).
  • Re-size connecting rods (big end & sometimes small end).
  • Turn & Index crankshaft.

Source of this information: RPM – Ron’s Precision Machine Santaquin Utah