I have a carbed 383. Im kinda stumped on this one. I have a misfire. It idles choppy at idle, which is normal because of the cam. When I rev it up to 2500, the motor still shakes. Everything is new, motor was just built last year. I put new plugs in, with new MSD wires that go to a MSD pro buillit distributer. My boss was saying its a little normal because the engine should be run when its 40* because its to cold out for it. Its a 525 HP 383, so its not the run of the mill small block chevy. I know it runs rich, because of the cold weather, maybe that could be the cause, but other the re-adjusting the carb, im lost.

 

Cold air should make it run lean if it's tuned for warm air.

Check the basics - spark, compression, fuel.

Are the spark plug wires routed to the proper spark plug? Wouldn't be the first time that bit someone, even experienced wrenches. Do all the plugs look the same? Since you said it's running rich, are they all equally black? Do you have a dead cylinder? Could be plug, wire, cap, distributor. Wouldn't be the first time a new part was defective.

Have you checked compression? Valves adjusted properly? Flat lobe on the cam?

Vacuum leaks, plugged fuel passages are common causes of misfire.