Project Racer Part 8: Nissan SR20DE S4 Cams from Jim Wolf Technology

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Performance cams also have more overlap between the intake and exhaust stroke.  This is the period where both the intake and exhaust valve are open at the same time. The overlap is due to the valves staying open for a longer period of time. We want overlap because the momentum of the in rushing air/fuel mixture forces more mixture into the cylinder as the piston starts its intake stroke. As the rpm goes higher, the faster the air/fuel moves and by leaving the intake valve open longer and lifting it higher, the more fuel air mixture can be sucked into the cylinder making a bigger bang when ignited.

The exhaust valve is also lifted higher and held open longer giving exhaust gasses more time to escape fully.  Making the engine suck in more combustible mixture and spit out more exhaust is said to be improving its volumetric efficiency, As a result, we get more power. The drawback to a big cam is that the engine will have a rough idle and lose some bottom end power as the exhaust will spit back into the intake at low rpm when the inertia of the inrushing mixture isn’t enough to prevent backflow.

 

WPC treated JWT SR20DE H4 cams
For less friction and longer life, we WPC treated our JWT cams before we put them in.

Now that we’ve covered the basics of cams and their function, lets get down to the details of what makes these JWT S4HL cams worth installing. First and foremost, these cams utilize the OEM valve springs, rather than replacing them with costly, lower quality aftermarket springs, as most other aftermarket camshafts do. Also, unlike other cams which are usually either regrinds or rewelds, the S4 cams use the same production process that OEM cams use; the same billet iron alloy, and the same chilled cast iron process. This as a result, allows for the most reliable valvetrain geometry, more horsepower, and a longer life of the cam.

JWT S4HL Camshaft Specifications:

  • Intake Duration: 266°   
  • Lift. 482″
  • Exhaust Duration: 266° 
  • Lift .464″
  • Lobe Centerlines: 111°/117° 

Benefits: Good power above 5500 RPM
Detriments: Low end torque not as strong

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