Zenith Carb Rebuild

[ed - 911T]

(duplicate - original posted in off-topics forum)

I'm rebuilding the zenith carbs in a '71 911T… but I discovered something intriguing concerning the little accelerator pump check valves under the injector. I found all three in one carb just lying in the bottom of the float bowl - not where they belong, and in a place where they were clearly put by a previous owner, cause it would be impossible for them to come out of their correct position once the carb was bolted together. (note - I have not yet put the new o-ring on the clean injector in this photo)

Also, in the other carb all three check valves were totally missing - no where to be found ??

Here's my question - how does this valve actually work and why do I need it ? I have been driving this car for 20 years without any - apparent - trouble with throttle response, acceleration, etc. Although maybe if there were a subtle problem I wouldn't know it… which suggests (maybe ?) this valve performs an insignificant function - if any ?

Finally, if it is important to include this valve in the rebuild does anyone know where I can buy just three ? Oh, and I also need one fuel strainer for the banjo fitting.

Thanks for any advice/help.

[bobolsn]

Ed,

I wish I could help, cause I have a 71T and will be in your position in due time (hopefully shortly). There have been several threads that discuss the functions of certain components. Also, they mention that certain components do have have any value (they suggest plugging them). Do a search.

Do you have the link to the Zenith carb manual?

Keep us posted, particularly anything you find out and your success in the rebuild.

Bob

[1QuickS]

These are a gravity actuated check valve that closed when the throttle pedal is released to allow an upshift/downshift. So, with this valve closed, replacement fuel is drawn into the accelerator pump body where it is ready for the next throttle application.

Without the valve the only way fuel would be drawn into the pump is by the difficulty for air to pass through the .3mm hole in the tip of the injector by which the resulting vacuum in the injector would allow some fuel to be drawn into the accelerator body. A larger tip hole diameter would probably disable the accelerator squirt altogether.