3/4-16 THREADW/NIPPLE, W/O RELIEF VALVE LYCOMING O-235, IO-320 SERIES LIO-320, AIO-320,AEIO-320, O360, IO360, AIO-360, HIO-360, LIO-360, TIO-360, LHIO-360, AEIO-360, O-540, IO-540, HIO-540, TIO-540, AEIO-540, LTIO-540, TIO-541, IO-580