74 Dart. Headers vs manifold.

pishta said
adding $1000 EFI wont improve gas mileage either, unless your way out of tune on a carb. 14.7 stoich is stoich: from a carb or an injector. Headers usually lean out a manifold tuned carb. Dyno results on a tuned carb over EFI are not night and day, but cold start driveability is. Carters are usually pretty flat across the curve AFR wise. Take your car to a tuneup place with an exhaust gas analyzer and have them tune the carb. Or buy a $150 wideband and a strip kit and do it yourself and still have the ultimate carb tuning tool in your toolbox. If you want better fuel economy, increase your compression ratio, cam down in duration and go to a shorter rear end.

Yeah if you watch a well tuned carb on an air fuel gauge compared to EFI it's a totally different story. Even well tuned carbs aren't capable of the kind of consistency and accuracy that a decently tuned EFI system can give. Maybe on a dyno it's not a "night and day" difference, but dyno's are about maximum power, not about maximum fuel mileage as driven on the street or even the best driveability on the street. Two completely different things. All you're getting a good picture of on a dyno is WOT, it's a tiny component of a carb's overall tune and a part of the tune that's barely even going to be used on a driver. It's easy to tune WOT compared to tuning all the transitions, that's where you lose efficiency. It's not like a carb will hold your AFR at 14.7 all the time. Not even close. And that's where EFI improves mileage- it's about how consistent the AFR is, and EFI does a much better job on average if you look across the board.