The Johnson Variable Duration Hydraulic Lifter is manufactured for low vacuum applications.  It was engineered for Dirt track racing specifically to increase low-end torque and increase vacuum to meet class requirements with the biggest cam you can run!  This makes it perfect for high performance street cars wanting more vacuum, more torque and greatly improved idle.

The body is machined from a special formula of wear resistant hardenable iron.  The internal piston is extra long and is fitted with a light weight, quick acting, full flow check valve plate, for quicker response and better performance through the operating range. Johnson Variable Duration Hydraulic Lifters assembled with an oil metering plate and a precision coined push rod seat; this provides metered oil to the valve-train insuring proper oiling through the push rod.  The metering plate is crucial in maintaining the proper oil pressure through the entire operating range of the engine.