Inelastic electron scattering form factors away from the closed sd -shell are investigated. This investigation covers the low-lying states in 29Si , which is considered according to the many-particle configuration mixing shell model as the 16O core, plus thirteen nucleons distributed over the entire sd -shell orbits. The investigation concentrates on the perturbative role of the core, which is called core polarization effects, on the inelastic electron scattering form factors. Core polarization effects are taken into consideration through the excitation of nucleons from 1 s and 1 p core orbits, and also from the 2 s -1 d valence orbits into higher shells, with 2ℏω excitations. Core polarization matrix elements are calculated with the M3Y effective interaction. For the sd -shell model space, a new Hamiltonian, based on a renormalized G -matrix, USDB, is used. All calculations are performed without adjusting any parameters.