Quote Originally Posted by timkins
I have a 350 SBC in my street rod and after it sits for a couple of days I get a real clattering from one lifter that goes flat. It goes away after a few minutes (3-5 minutes). I have changed the rocker nuts as one of them would not stay set and would loosen up and start the clattering again. There is really nothing else wrong with the motor. I run about 55lbs oil pressure when driving and about 30lbs at idle. My question is; is it feasible to change the lifters, push rods, rocker arms and nuts on a motor that you are not sure of the rest of the internals or the mileage on the motor. It burns no oil and does not leak.

If it pumps back up after a starting, the oil pressure is bleeding down as the engine sits. Either the clearance is too great between the internal plunger and the main body; or the check valve at the bottom of the internal plunger is leaking. Add a quart of trans fluid to the oil and drive it for a bit. The trans fluid will sometimes free up sticking mechanisms in the lifter.

Lifters are cheap but you are taking a chance putting new lifters on an old cam. I'd try to narrow the one lifter down, pull it out and take it apart. It may be gummed up and just needs cleaning. You may be able to rebuild it using parts out of another lifter. Worst case, if you do change the lifter treat it like a new cam and "break it in".