Extreme Engine Tech: Jim Wolf Technology's Turbo Nissan QR25DE Powerhouse Part 2

This aluminum plate was used during boring and honing to simulate the distortion that bolting on a cylinder head creates.  This way when a head is actually bolted on, the bores will be round.

To help stiffen the block to improve bore stability and ring seal and to improve head gasket seal by reducing cylinder shift, we partially filled the water jackets of the block with aluminum filled epoxy resin. The aluminum filling helps the filler match the expansion rate of the block.  We filled the block to the level of the piston rings at BDC. We feel that this won't effect cooling much as some engines have water jackets this short.  The filling will reduce flex in the block.

The engine was bored 1mm oversize to accommodate the new pistons.  During boring, a torque plate was used.  A torque plate is a special metal plate that is bolted to the top of the head during machining to simulate the distortion that bolting on a cylinder head will apply to the block when its bolts are tightened.  The torque plate helps ensure that the cylinder bores will be round when the head is attached to the block.

In this photo, you can see the block water jacket epoxy filling and the bore finish.  The bores were made extremely smooth with a 600 grit final hone with a cork bonded plateau hone as a final step.  After honing the bore was WPC treated.

By ensuring a rounder bore, the torque plate greatly helps improve the ring seal and reduces piston scuffing thus improving the life of the rings, bore and piston.  As a side effect, power is increased as well.  To ensure good gasket sealing with a metal head gasket, the head mating surface was machined flat in a mill and lapped on a surface plate.

The piston coolers are the copper colored nozzles that squirt oil onto the underside of the pistons.

Turbocharged engines create a lot of internal heat, much more than your typical naturally aspirated engine.  This issue is compounded in road racing where an engine is stressed for up to 40 minutes at a time compared to mere seconds as a street car or drag car will be.  To help the pistons shed heat JWT installed piston coolers from a Honda B18C engine.