Automotive Intake Manifold Flow Control Valve

An intake manifold had been designed with four flow control valves and a stop, each affixed to a common shaft with two Slotted Pins. The valves are cast magnesium and the stop is plastic. The customer complained of poor efficiency due to nesting and interlocking of pins in their feed equipment. Quality issues had also been tied to the Slotted Pin. These issues consisted of high insertion force, skiving, cracking of the host, and increased total run-out over the shafts length. A solution was required that would improve efficiency, reduce or eliminate the occurrence of damage to the host materials, and lower insertion force to prevent deflection in the shaft.


app coiled pin automotive intake manifold flow control valve
app coiled pin automotive intake manifold flow control valve close up
All spring pins are designed with a pre-installed diameter larger than the intended hole. Pins are sized to the hole diameter during installation and the resultant interference provides retention. Slotted pins are generally considered a ‘heavy duty’ solution manufactured with thick, rigid walls. It is critical that the strength and flexibility of a pin be properly matched to the host material or damage to the host material can result. Soft materials such as magnesium and plastic require a solution with greater flexibility to reduce insertion force and limit stress. Slotted Pins are manufactured with stamped chamfers – a process that is inferior to the swaging or coining operation used to form a Coiled Spring Pin’s chamfers. Coiled Spring Pin chamfers are concentric and smoothly blend into the diameter of the pin. This prevents the skiving and alignment problems commonly associated with Slotted Pins. Because Coiled Spring Pins have a seam rather than open gap they cannot nest or interlock in automated equipment.

SPIROL Engineering recommended a light duty high carbon steel Coiled Spring Pin for use in this application. Light Duty Coiled Spring Pins are designed with the enhanced flexibility required for installation in soft host materials such as plastic and magnesium. This significantly reduced insertion force and eliminated the associated cracking and shaft run-out problems.


Light duty pins provide this flexibility while maintaining high strength in proportion to the materials in which they are installed. The Coiled Spring Pins’ superior chamfers or end condition corrected the skiving issue associated with the Slotted Pin and because they cannot nest or interlock in automated feed equipment the customer’s downtime was reduced. This standard Coiled Spring Pin provided an economical solution that increased efficiency, reduced scrap, and improved product quality. These benefits were provided while requiring no modification to the application or installation equipment.

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