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



The good thing about choosing an engine shop like 5523 Motorsports that specializes in building Nissan engines is the wide inventory of parts specific to Nissans that they carry.  In many cases, an engine builder will just order oversized ACL bearings with .001″ extra clearance, slap them in, and call it a day.  Excessive bearing clearances often result in low engine oil pressure and shit bearing life.  Nick prefers to take his time optimizing bearing clearance to OEM spec.  There's no short cutting here. This detail is just one of the things that separates 5523 Motorsports from your average engine shop.  

While Nick worked on gapping the rings, I measured the diameter on the crank journals in an attempt to make myself somewhat useful.  (Although I probably just got in his way more than anything else.) The crankshaft journal diameters were the last piece of the equation that Nick Hunter needed to select bearing grades and fine tune clearances.  Put simply, clearances are calculated using the following basic equation: 

Main bearing clearance= Main bearing housing – (top + bottom shelf thickness) – journal diameter.

Once the bearings were sized, Nick Hunter cleaned out each of the oil passageways in our 63.5mm stroke crankshaft.  Any debris left over from the de-stroking or nitdriding process could easily destroy a main or rod bearing… and that would suck.

Next, Nick Hunter gapped each pair of compression rings for a specific cylinder in the engine. Much like bearing clearances, ring gap has the potential to make or break a race engine. An oversized ring gap can lead to excessive blow-by, poor oil control, and power loss.  While on the other hand, too tight of a ring clearance can cause cause the ring ends to butt, grab a cylinder wall and potentially lead to piston land failure.  From years of experience, Nick Hunter has dialed in the ideal ring gaps suited for specific ring materials and dimensions as well as engine power and application.  This is one of those types of secrets that engine builders take to their grave.    

The oil squirters were cleaned, inspected, and reinstalled before the crankshaft.  With our short stroke and long rod, we had plenty of piston to oil squirter clearance.  Insufficient squirter clearance can be a problem with many aftermarket pistons for stroker and even sometimes factory stroke applications.  Be sure to check for this if you're building an engine.

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