Engine Blueprinting (Part 2)

Today's CAD programs offer definitive X-, Y- and Z-axis depictions of specific blocks, providing you have access to these programs.

Blueprint specifications (shown here is a GM LS block) include all dimensional aspects of a component per the design parameters.

Block manufacturers such as Dart provide blocks that are already correct in terms of bore centerlines and deck dimensions and planes. When dealing with such high-quality aftermarket blocks, only finish-machining to achieve desired clearances is needed. In essence such blocks are already blueprinted in terms of crank centerline, cam bore location, cylinder bore and lifter bore centerlines and angles, and deck symmetry and height. all photos by author

The use of a CNC machine allows easy indexing to the main bore centerline as a machining reference, permitting precise deck machining for desired height.

CNC probing records existing cylinder bore location. This derived dimension can then be compared to design data, instructing the machine to then bore to correct centerline and angle, if needed.

CNC machining eliminates the need for dedicated bore centering fixtures. Programming instructs the cutting head to follow the correct path and per-application desired diameter.

Today's engine-builder-specific CNC machines offer ready-made programs for machining specific make/model blocks to achieve precise dimensional control.

The main cap fasteners that will be employed during the final assembly should be used throughout the machining process, from start to finish, to eliminate any potential variables in terms of main web/cap applied stresses.

Lifter bore correction (in terms of centerline location and bore angle) can be accomplished either with a specialty fixture dedicated to a specific block, or via CNC program.

Again, in order to retain consistency, the final-assembly-intended cylinder head fasteners should be used during torque plate installation prior to cylinder bore honing.

Elimination of block dimensional inconsistencies plays a vital role in achieving both peak horsepower and engine longevity.