No Bronze Guides, Any Reason?

actually reaming is with a reamer
I use carbide
there is also broaching and sizing with balls
all have their places
the balls push the new guide into the old cast iron
especially with spiral wire guides
also called ball burnishing
on valves
you have Ti, hard chrome, flash chrome, steel, stainless and Inconel and some other exotics
you do each different
for example Chrysler 440 motorhome motors came with SIL-XB intakes and Inconel headed exhausts all with industrial hard chrome stems
The 413 motorhome had sodium cooled exhausts with hard chrome 7/16 stems as did the HD flathead We used the flathead exhaust in the Barney Navarro/ AMC indy 6 cylinder turbo project could run 1200 hp all day long

the knurling is for guides with no inside groves
not only locks the guide but is mostly to provide some places for lube to hide