I have an '89 350 with aluminum heads, good exhaust, and a few other mods. For max. performance from my stock cam I have 1.6 rockers, and set the lash to slight lifter noise and then only 1/4 turn tighter.The motor runs strong and revs but....
the lifters tick a little bit and this may not be good for rollers. I checked the filter after 2000 miles and found , with a magnet, some very fine magnetic particles there, not a huge amount, but made a nice fringe around my 1 in. magnet. Usually in a race motor I find some aluminum and bits of babbit, but not much steel or iron.
Where could this have come from I wonder. I'm wondering if my rollers and/or cam is going south.

 

my 87 has seen 6000+ & feels like it wants more,just afraid to go past the 6200/6300.all internals are stock,just have a edelbrock intake,670cfm street avenger,k&n,and some ignition mods....did you do a pre/post oil change?? both are really important for that reason,when a new part is breaking in,metallic pieces will be found

 

I think 6000k + not much use w/ stockish setups...I went around rockers and springs w/ magnet and picked up some metal so perhaps rockers, spring shims are source of metel. moved rocker settings a tiny bit and it seemed to help w/ noise just relocating them...