To clarify my question, after passing through the carb ports, does the air/fuel mixture enter a common area before going down the runners to the various cylinders...?

The reason I ask, is to me it would make sense if the air/fuel mixture could mix from each port. That way if the A/F mixture was a bit lean from one barrel, it would mix with air coming through the other barrel and even out the mixture a bit. If kept separate you could have 4 cylinders running rich or worse 4 running lean.

With my EFI, the narrow-band O2 sensor is on only one exhaust manifold. So if the barrels are kept separate, one side would run at 14.7 AFR and the other could be rich or lean. If that is the case, maybe I should put an O2 sensor on the other manifold with a circuit to switch back and forth between the two cylinder banks.

If one of the injectors were to clog or become faulty, the fuel mixture would become lean going through that barrel of the Throttle Body. If there was a common area below then the mixture would even out and the O2 sensor would compensate.

Or does each barrel feed 2 cylinders on each side of the engine which would mean my O2 sensor is seeing exhaust created by both barrels (injectors).

I have a wide-band sensor that is after the exhaust pipe Y and so samples from both banks. However sometimes it show richer and sometimes leaner while the narrow-band shows it is switching so it is around 14.7p

Thanks!

Bruce
The manifold on my 455 has an open chamber below the carb ports.

Dennis

RF_Burns wrote on Tue, 12 January 2021 16:03

To clarify my question, after passing through the carb ports, does the air/fuel mixture enter a common area before going down the runners to the various cylinders...?

The reason I ask, is to me it would make sense if the air/fuel mixture could mix from each port. That way if the A/F mixture was a bit lean from one barrel, it would mix with air coming through the other barrel and even out the mixture a bit. If kept separate you could have 4 cylinders running rich or worse 4 running lean.

With my EFI, the narrow-band O2 sensor is on only one exhaust manifold. So if the barrels are kept separate, one side would run at 14.7 AFR and the other could be rich or lean. If that is the case, maybe I should put an O2 sensor on the other manifold with a circuit to switch back and forth between the two cylinder banks.

If one of the injectors were to clog or become faulty, the fuel mixture would become lean going through that barrel of the Throttle Body. If there was a common area below then the mixture would even out and the O2 sensor would compensate.

Or does each barrel feed 2 cylinders on each side of the engine which would mean my O2 sensor is seeing exhaust created by both barrels (injectors).

I have a wide-band sensor that is after the exhaust pipe Y and so samples from both banks. However sometimes it show richer and sometimes leaner while the narrow-band shows it is switching so it is around 14.7p

Thanks!

Is it worth the effort to make a modern fuel injection manifold with injection for each individual cylinder for the 455?

Randy Hecht
Roswell, GA
1974 Canyon Lakes GMC Motor-coach