Hello,

Have a 68-70 oldsmobile rocket 350 with '74 7A heads. Hydraulic flat tappet lifters are collapsing. I've had these lifters for about 3 years, raced with them a few times. Probably only 3-4 hours of engine running time in those 3 years, it say mostly. Engine was rebuilt when they were put in and always taken good care of. The lifters have gone soft and caused a tapping. If I press the pushrod in and out i can manually pump them back up with oil and they become solid, but after a few cranks of the engine they go soft again. My engine has good oil pressure. I disassembled and the lifters, cam lobes and pushrods are in excellent condition. Only thing damaged is bottom of rocker arms as they are bottoming out on the studs when tightening. What is the reason for this?

Specs:

Crane cams aluminum roller rockers - 80-1.60, -11

Trick flow pushrods 8.500 .080

Howards cam performance hydraulic lifters 91411

Howards cam hydraulic flat tappet camshaft CL510991-08

Thank you,

Steven