PEP HIGH PERFORMANCE & OEM INTAKE / EXHAUST VALVES

PEP Stainless Steel Valves are made from premium 21-4N material. The stem is chromed and micro polished for an exceptional finish.

JF or Jet Flow indicates an undercut stem for less weight and increased air flow.

PRO indicates a severe duty valve for high endurance applications.

P7Series represents the latest in valve technology, the stem finish is designed to maintain an oil film under extreme conditions, avoiding scuffing and premature valve failure.

PEP valves are available in many configurations from street performance to all out racing.

A traditional reciprocating internal combustion engine uses valves to control air and fuel flow into and out of the cylinders, facilitating combustion.

Valvetrain is an all-encompassing term used to describe the mechanisms and parts which control the operation of the valves.

Layout

Valvetrain: The valvetrain consists of valves, rocker arms, pushrods, lifters, and the cam shaft. Valvetrain opening/closing & duration controls the amount of air and fuel entering the combustion chamber at any given point in time. Timing for open/close/duration is controlled by the camshaft which is synchronized to the crankshaft by a chain or belt.

Valvetrains are built in several configurations, each of which varies slightly in layout but still performs the task of opening and closes the valves at the time necessary for proper operation of the engine. These layouts are differentiated by the location of the camshaft within the engine:

Overhead camshaft
The camshaft (or camshafts, depending on the design employed) is located above the valves within the cylinder head, and operates either indirectly or directly on the valves.

Cam-in-block
The camshaft is located within the engine block, and operates directly on the valves, or indirectly via pushrods and rocker arms. Because they often require pushrods they are often called pushrod engines.

Camless
This layout uses no camshafts at all. Technologies such as solenoids are used to individually actuate the valves.

Parts

As stated above, the valvetrain is the mechanical system responsible for operation of the valves. Valves are usually of the poppet type, although many others have been developed such as sleeve, slide and rotary valves.

Poppet valves typically require small coil springs, appropriately named valve springs, to keep them closed when not actuated by the camshaft. They are attached to the valve stem ends, seating within spring retainers. Other mechanisms can be used in place of valve springs to keep the valves closed: Formula 1 engines employ pneumatic cylinder heads in which pneumatic pressure closes the valves, while motorcycle manufacturer Ducati uses desmodromic mechanisms to manually close the valves.

Depending on the design used, the valves are actuated directly by a rocker arm, finger or bucket tappet. Overhead camshaft engines use fingers or bucket tappets, upon which the cam lobes contact, while cam-in-block engines use rocker arms. Rocker arms are actuated by a pushrod, and pivot on a shaft or individual ball studs in order to actuate the valves.

Pushrods are long, slender metal rods seated within the engine block. At the bottom ends the pushrods are fitted with lifters, either solid or hydraulic, upon which the camshaft, located within the cylinder block, makes contact. The camshaft pushes on the lifter, which pushes on the pushrod, which pushes on the rocker arm, which rotates and pushes down on the valve.

Camshafts must actuate the valves at the appropriate time in the combustion cycle. In order to accomplish this the camshaft is linked to and kept in synchronisation with the crankshaft (the main shaft upon which the pistons act) through the use of a metal chain, rubber belt or geartrain. Because these mechanisms are essential to the proper timing of valve actuation they are named timing chains, timing belts and timing gears, respectively.