Start Up Oil Pressure

[AMXguy]

What would cause a good condition 440 to rattle and clatter for about 20-30 seconds on start up?  it misses and clatters then cleans up and runs great with more than enough oil pressure, about 70 psi cruise and 30 idle.

It's like a bad lifter, only it sounds like all the lifters.

[Chryco Psycho]

sounds right , 4-5 lifters on the open valves will bleed down with valve spring pressure & it takes a few seconds to pump them back up .

[AMXguy]

But it's worse than it has ever been, lots worse.

the only thing different is the Joe Gibbs 20-50 oil and a Bosch filter.  would the heavier oil make it bettwer or worse or any difference? and do these type filters have a backflow valve?

[Chryco Psycho]

probably the thicker oil would make it worse , cold 20-50 flows slowly