So I had a 455 in my 65 GTO and it wouldn’t turn over. After putting some gas and starting fluid in the carb it still would not turn over. I tried for a good 5-7 minuets cranking the engine, getting out and spraying the starting fluid, cranking and still nothing. After I gave up I got out of the car and heard a clicking sound. Sounded like it was coming either from under the valve cover, intake or carb. I came across a deal on a 428 so I swapped out the engines and today I went to fire up the 428 and had the same problem of it not turning over and the same clicking sound was there after about 5-7 minuets of trying to get it to start. The clicking goes away after about 5-7 minuets of it sitting. It’s not electrical, I don’t think, because I disconnected the battery and it still did it. Plus it sounds like it’s in the engine somewhere. I figured out why the 428 wouldn’t turn over but now I’m concerned about this clicking sound. Nothing was switched over to the 428 from the 455 either. Two completely different engines and the same clicking sound after not turning over. Any ideas??