I have an intermittent misfire that is puzzling me:
• 1972 Chevy K20 with 350 small block
• Delco HEI distributor
• Eldebrok 1406 carburetor with newly installed pressure regulator
• Installed new plugs and wires last week. Old plugs were black and smelled rich
• Installed deadhead pressure regulator
• Timed engine at 12 degrees BTDC
• Adjusted jets on Eldebrok 1406 using vacuum gauge - vacuum around 17psi. Not any experience with 1406, but jets are within a turn from being totally closed (seems odd to me).
• Intermittent misfire. Noticeable around 1200 rpm. I have dual exhaust with not cross over and observe misfire from both tailpipes.
• The misfire can be explained “runs along with intermittent, short surge”
I really don’t want to start throwing parts at the problem, so I am looking for additional troubleshooting ideas.
I think you adjusted the idle mixture screws, not the jets. You might need to change the jets if your plugs are black ans smelly. I'm no expert with Edelbrock style carbs.
As far as the misfire/surge...check for vacuum leaks by spraying carb cleaner at the base of the carb. How new is the timing chain? When you put a timing light on it, does it stay steady?
When did this mis start?