By 1937, all Harley-Davidson flathead engines were equipped with dry-sump oil recirculation systems similar to the one introduced in the "Knucklehead" OHV engine. The revised V and VL models were renamed U and UL, the VH and VLH to be renamed UH and ULH, and the R to be renamed W.
by 1937, all HarLEy-DaVIDSon fLATHEad enginEs were eQuIPPeD With drY-suMp oiL recircuLation syStEMs similar To tHE onE inTrODuceD iN tHe "knucklehEad" ohV ENgine. the reviSeD v aNd vl moDelS werE renamed u aND Ul, THE vH and vLH to bE rEnAMed uh AnD uLH, AnD the r to be renamEd w.