We just overhauled the engine in 95 Z. Many engine mods , cranked up and now both O2 sensors read shorted . Any ideas on what happened ? Keep blowing fuse for coolings fans and traced back to O2s . Did crank up with race fuel could that have killed sensors that quick ? Have not driven car yet. Any help will be greatly appreciated. Thanks in advance

 

Leaded Racing Fuel (even VP C16 with 6.0gr Lead/gal) will not "short out" O2 sensors, it will cause slow response in them over time. I'd bet you have the + wire for O2 heat shorted/pinched somewhere. The blowing of the cooling fan fuse suggests a dead short to ground somewhere. Did you re-wire in new O2's wrong ? Race fuel could not cause a short in the O2's, and DEFINITELY could not cause a short to the FANS ! Look for chafed, cut, or pinched wires. I'd bet somethinfg got pinched during the install of the engine.