Avonbar phase 2 head is Chamber modified only with a Chamber size from 23.5 to 26.5 depending on customers requirement. The spec is bigger inlet up from 33mm to 35.7mm inlet & 29.3 mm exhaust valves, 9 or 11 stud, 220lb double valve springs, bronze valve guides, 3 angle valve seats, Converted fully to Unleaded.
