JIMS, Powerglide hydraulic tappet. Standard .8420" O.D.

Jims PowerglideT tappets will give you a superior hydraulic function when compared with OEM style equipment; a billet steel body with hand-honed hydraulic unitcavity and an oil fed axle. To get full power; you must have zero valve lash and eliminate collapsing of the hydraulic unit as is found in the OEM unit; also called ''the shock absorber syndrome''. Failing to keep the valve open the full amount results in power loss. The Jims Powerglide tappets come as close to a solid tappet as possible; but are still able to compensate for heat expansion. They will even work well with solid style camshafts. Fits as a direct improved replacement for OEM 18538-99C.