Not very often (never!) That I can offer any insight.
I put KB167's in my 318. Six of the deck heights came out at zero and two were a couple of thou down. I called that good.
I guess I was lucky.
That's great. I'm thinking about using KB167 's with promaxx heads. The promaxx offers more for the money than the speedmaster's. Promaxx heads come with a 5 angle valve job and hand blended bowls.