Well that's good news about being 180⁰ out. It's the carb I took off the old 400. It ran fine and it's probably 2-3 years old. It's a 750 holley, should be a good fit for this engine. My dad suggested having someone crank the engine while I slowly adjust the dizzy until i have some success. I told him I'm going to reach out to you all first haha.No. It won't run for even a second if you're 180 deg off. Are you trying to break in an engine with a new carburetor? It's preferable to use one that you know ran OK even if it's too small for your engine.