Strange oil pressure after I frame

[Nater1977]

So I Finished an in frame today 2008 CM871 fired it up and watched oil pressure it was at 60 Psi less Then ten seconds and dropped to 28. I turned it off checked everything over and restart same exact pressure drop in less that ten seconds. Maybe this is ok, but it is weird to me.
Updated the oil bypass and i did add dimes to the oil pump, Not a new pump has shims in it.
Any ideas? Or is this normal. Maybe the pump hitting the high pressure limit and dropping pressure?