If you are trying to determine whether or not you have a 305 or 350 engine, there are several things that you can look for. First and foremost, compare the overall size of the engine. The 305 is much smaller than the 350, so if your engine looks larger than usual then it is likely a 350. Additionally, take note of any emblems on the valve cover – most vehicles with a 305 will have “305” stamped right into it while those with a 350 may just say “Chevrolet” instead. Another way to tell them apart is by looking at their spark plug thread pitches; most Chevrolet V8 engines use 14mm thread pitch but some models with 305s used 18mm threads instead. Finally, check out the displacement numbers found in both engines as they usually indicate which one you have; 305s typically had 4-inch bore diameters while 350s were slightly bigger at 4.00 inches or more. With these tips in mind, it should be easy for anyone to quickly identify whether they have a Chevy 305 or Chevy 350 under their hood!