hey on the bottom of b-series heads whats the numbers mean...like theres three circles i think...and i know the first ones the year, but what about, like on my B16 the PR3-3 because I have a B16a from 90 head that says PR3-3, a type R head from 2000 that says PR3-3 also, but my friends 96 type R head says PR3-2 wassup with that?
