If by pushing you mean rating the film at a higher EI during exposure then you will get lower densities. You won't be able to compensate for lost shadow detail by developing longer. Exposure controls density, development controls contrast.(posted 8381 days ago)You will lose shadow detail; the low zones are significantly affected by underexposure. You will get a contrastier negative because the high zones won't be affected as much; Zone 8 will be less dense but not as thin as, say, Zone III compared to film exposed at your normal EI. If you develop the film to get the same density for Zone 8 you'll get a "normal" looking print with dark, impenetrable shadows -- I'm not saying that's bad, it may actually be the effect you're looking for.