S&S, steel breather valve. STD

High quality steel breather valve for use as an original replacement or for high performance.
Note: S&S breather valves come with elongated breather ports to increase the duration of the vacuum, allowing more oil to be drawn from the heads. This has no downside on any model year, whether original or Big Inch engine.
Note: Steel breather valves require steel breather valve spacers. Plastic breather valves require plastic spacers. Do not mix steel and plastic parts.
Note: An oversized .030" breather valve is available to save worn or damaged crankcases, such as reference 518662. A JIMS breather bore reamer (MCS 978343) will ream the damaged bore to +.030" so a +.030" breather valve can be used.
Technical tip: The opening timing of the S&S breather valves, for late 77-84 Shovel and 84-99 Big Twin Evo models only, was changed by S&S in the year 2000. This is done to improve oil scavenging and reduce oil carry-over in high-performance/large-displacement engines. The old opening was at TDC and closing at 65° after BDC. The new opening is at 17° after TDC and closing at 82° after BDC. The old timing specification can be obtained by installing the timing mark on the breather valve gear one tooth clockwise from the timing mark on the camshaft gear. In addition, the oil drain hole in the breather valve cavity (opposite the drive gear), previously a round hole, has been elongated (made longer) to increase the duration of the suction to the crankcase breather 'settling' cavity. The new specifications are not useful on most original engines, but they are harmless. The breather windows in S&S crankcases typically open at 7° after TDC and close at 92° after BDC. Builders using other crankcases can modify the crankcase breather opening to achieve these specifications for maximum breather efficiency and performance.


Specifications


Brand
S&S


Application
L77-99 Big Twin (Excl. TC)


Material
Steel


Packaging weight
0.167 kg


HS Code
84099100


Motorcycle family
BIG TWIN, DYNA, FX, FXR, SOFTAIL, TOURING


Original name
S&S, steel breather valve. STD