The first 9 key, Single Roller Timing Set for the 364-401-425 Buick Nailhead engines. This timing set is also the ONLY roller timing chain set available for the Nailhead engines. The single roller timing chain features a 1/2 inch roller which is much stronger than the 3/8 inch roller used on double roller timing chains and thicker link bars which have more material around the pin hole to prevent breakage. The sprockets are hand filed and then vibratory tumbled twice, once before heat treatment and again after being heat treated. This knocks off any hanging burrs that would otherwise end up in the oil and peens and work hardens the surface for increased durability. The end result is this single roller timing set being much stronger than everything else available.