The TWIN CAM 88 was released in 1999.Harley Davidson original nicknamed this a “BLOCKHEAD” due to the fatter top end.This was not a nickname that caught on.The TWIN CAM has a 2 piece rocker box cover and the centers of the covers look like they have a block sticking out in the middle of the side.They have 2 cams unlike any of there predecessors, improved oiling system and 60% more cooling fins.Their are many models of TWIN CAMS the original is the 88 built from 1999-2006 which was a 1450cc engine.The next was the TWIN CAM 88B (B stands for counter balanced),2000 they released the 95 TWIN CAM a 1550 cc engine used in CVO models, a 96 TWINCAM 1584 cc model used in the STREETBOB, SUPERGLIDE and DYNA MODELS.The 103 TWIN CAM 1690 cc engine was used in TOUR MODELS and the 110 TWIN CAM 1802 cc was used in CVO models.