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

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JWT S2 cams are ground on new billets and can usually be installed without reshimming for valve clearance.

JWT replaced the cams with their S2 cams.  The S2 is their larger more radcal grind which has been proven to make 10-12 more hp at higher rpm and to work well with turbocharged engines.  The stock valve springs float at a pretty low rpm and JWT used their higher performance valve springs.  Lightweight titanium retainers are used as well. This combo will allow us to safely turn up the rev limiter to over 7000 rpm if needed.

Here are the JWT valve springs and titanium retainers in place on the head.

Before assembly we made extensive use of WPC treatment. WPC treatment is a Japanese born process where metal surfaces are bombarded with very tiny ceramic shot at extremely high velocities. Special antifriction additives like tin or zinc powder and molybdenum disulphide are added to the mix and are embedded into the surface. The result is an extremely smooth friction free surface with self lubricating properties. The shot also compresses the metal on a molecular level near the surface, refining the grain, creating a zone where it is very difficult for micro fatigue cracks to propagate. In this way WPC works very much like shotpeening for increasing fatigue strength of parts but on a finer scale. We WPC treated the crank, engine bearings, oil pump, piston pins, rods, block bores, rings, cams, valve springs and cam followers.  Nearly everything that rubs got the WPC treatment. Read about how the WPC process works here!

Our crank on the bottom has a lustrous milky color, a sign of WPC treatment.

The engine was assembled using a stock late model head gasket.  It is a strong metal head gasket that should hold up to turbocharging well.  Early head gaskets were prone to failure but Nissan improved the later gaskets and we made sure that one of these was used.

The stock late model headgasket is a MLS type (multi layer steel) that should hold up well to boost.  It has 3 layers with a stopper layer around the cylinder bores.  The old style gasket was only a two layer and was very failure prone, even on stock engines.