The Heart of a Record Breaker II: The Doctor is in

After completing his pre-assembly routine, Nick then turned his attention to sizing and specing the engine bearings.  Since this was going to be an all out racecar engine build, Nick Hunter opted to go with main bearings from Nissan's hopped up version of the SR20DET, the 54C.  The main bearings from the 54C variant of the SR20DET engine feature five oiling holes of varying diameter intersecting an annular groove.  In comparison, a standard SR20DET main bearing only has two oiling holes intersecting the annular groove.

To take full advantage of the 54C main bearings though, a complimenting annular oiling groove had to be cut into the block.  The 54C has this from the factory whereas the other variants of the SR20 only have an oil hole drilled into the main bearing housing which aligns with the larger hole in the standard SR20DET main bearing.  To cut the annular groove in place, Nick built this fixture using an old main bearing cap, angle grinder, and cutting wheel.  Want 54C main bearings done right?  5523 Motorsports is one of the few places that can do it.

This fixture might look a bit medieval giving the impression of questionable accuracy, but rest assured that it is complete with a Z-axis adjustment screw to control the cut depth to a couple thousandths of an inch.

Once the main bearing housings were altered, Nick bolted the main bearing caps and crankshaft girdle in place.  Using a bore gauge, he then measured each of the main bearing housings for diameters and roundness.

Knowing the unique diameter of each main bearing housing bore is one of the things that allows Nick to control the main bearing housing tolerances to .0001″.

Nick has a whole stash of different grade Nissan bearings, which vary in shell thickness.  This is what allows the bearing clearances to be optimized and matched for each of the crankshaft journals.  Check out the uber rare OEM Pulsar GTI-R main bearings.  Good luck ever finding a full set of these anymore.