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Colt Cams 4BT Tappet Set TAPPETS-4BT For 3.9L Cummins 4BT The Colt Cams 4BT Tappet Set is a great upgrade for the valvetrain in your 3.9L Cummins 4BT when adding a performance camshaft. Inconsistencies such as flat and even dished crowns on the tappets...