For primary, secondary or tertiary carbons, E2 can still happen with a strong bulky base. keep in mind, lots of times these rxn occur simultaneously, for example a primary carbon will favor SN2, however, that does NOT mean E2 will not occur. it simply means if you going for the SN2 product, it would be your facor to use primary carbon with a strong nucleophile. just as note, there is minor difference between a strong base and strong nucleophile when talkin about substituion vs elimination. a strong nucleophile will want to donates it electrons and attacks the carbon forcing the leavin group off (sn2). a good base draws also has electrons to donate, but it will tear off a proton (E2). of course, a good base can also be a good nucleophile, that is why we use bases like tert-butoxide, which does not attach onto the akyl group bc of steric hindrance.