Next, piston coolers from an SR20DET were installed. Piston coolers are nozzles that shoot oil from the main galley up to the bottom of the piston to help keep them cool under hard use. Aluminum loses much of its strength past 350 degrees and piston coolers help a high-compression engine stay cool under extended wide-open throttle use. Keeping the piston cool can also reduce the chances of an engine experiencing detonation under hard use. The piston coolers have a spring-loaded check valve to make sure that oil pressure isn't lost under low rpm and idle, but open at higher rpm when the oil pump's bypass circuit is activated. The stock SR20 block has bosses for the piston coolers already cast in place. The bosses must be drilled, tapped, and spot faced so the coolers can be installed.

Jim Wolf Technology routinely does this operation and it's pretty simple for any machine shop. Care must be taken to spot fact the bosses enough so the coolers' body clears the crank and the nozzle clears the piston skirt. SR16VE pistons have a notch in the skirt to clear the coolers but if you use some other piston, be careful and check this clearance when assembling the engine. Quite a few people have made this mistake and later wonder why their engines suffer from low oil pressure when the piston skirts shear off the nozzles! Like some of the other mods discussed here, piston coolers aren't absolutely needed for street or drag use but are a nice low-buck touch to help reliability under extreme conditions. The Nissan factory also uses piston coolers in its high-compression naturally aspirated motors, so perhaps there's a good reason for this.

Next, we focused on the crank. Fortunately the stock forged steel, fully counterweighted SR20DE crank is one of the stoutest units in the business and really doesn't require much work at all to sustain the highest power and revs. Usually an SR20 crank has very little journal wear and doesn't require much work for reuse. In most really low-buck applications, it can simply be inspected and reused. Since we anticipate some hard use, however, we sent our crank to Joe Castillo of Castillo's Crankshafts to have the journals polished and balanced, and the counterweights lightened and profiled for less windage drag. That last step isn't really necessary.

After magnaflux checking our crank for cracks, then inspecting it for other possible damage and straightness, Castillo put our crank on a lathe and profiled the counterweights. This removed a pound of weight and gave the counterweight a more aerodynamic contour. This should help reduce windage power losses in the crankcase, as the crankshaft has to spin in a dense cloud of turbulent air and oil. Since we anticipate a lot of high rpm long-term use, we didn't go crazy with lightening the crank; we simply removed from the counterweights about what was reduced on the pistons and rods.

Castillo then drilled out the oil passage plugs in the crank to facilitate cleaning and tapped the holes so screw-in hex plugs could be used. This is much safer and more secure than the stock pressed-in plugs. The journal oil holes were chamfered to create a reservoir for oil from the main bearing feed to improve oil flow to the rod bearings. Bob weights of the same weight as our rods and pistons were bolted to the crank, and the whole assembly was dynamically balanced. As a final step, all of the crank journals were micro polished to reduce friction and help improve bearing life. Although all of these steps aren't needed in a low-buck engine, they aren't particularly expensive either.