Weber IDF 40 mixture enrichment device ?

[Wfolland]

Just installed rebuilt duel weber 40 IDF -10 & -12( early models made in Bologna) on my 2L, everything runs fine except that I question rather or not the mixture enrichment device is kicking in at higher speeds. I have opened up the throttle and watched to see any fuel coming from the holes in the spray tube, and there is no indication of fuel. Any thoughts as to how I can determine if this system is working or not.

[RoyBatty]

Go drive it.
How does it respond with gradual acceleration to full throttle as you go thru the gears?

[Wfolland]

Is it possible that the height of my velocity stacks may have an effect on how much fuel is drawn from the tubes?, currently i have replaced the longer velocity tubes, that have built in screens, with very short velocity tubes ,without screens, in order to use sync meter to balance carbs. Your thoughts.

[Redline]

The standard "top hats" aren't very tall, so I don't imagine that matters much. I changed from the top-hats to taller trumpets and back and didn't notice any difference in the enrichment.

[Wfolland]

Think I'll remove the cover from one if the IDF's and check to see if there is any obstruction in the spray tube. Does anyone know what the size of the calibrated hole in the tube is ?

[rebar1111]

What do you mean by enrichment device? I thought that that was an option on those carbs and was to be used in place of choke plates. They should not be operational without a manual choke cable and only used to start a cold engine. Am I wrong?

[seabeelt]

The enrichment tube is a brass tube that is curved out over the top of the carb Venturi on the 10/12 and 13/15 series carbs. Supposedly at high air volume/open throttle conditions, the carb will draw fuel for the fuel bowl via a siphon effect to deliver more fuel directly into the Venturi. I have these on my13/15 setup. I have checked to make sure the siphon hole is open( it is very small within the carb body as compared to the tube size) and have not seen the tubes deliver fuel. Of course I have not wanted to hold the throttle open with no load at 5-6k rpm for any length of time to try and develop sustained (longer than a few seconds) air flow. Car seems to run fine and have good top end response, I just haven't seen any visual evidence that it delivers fuel.

Side note, the 70 series carbs do not have this tube

R/

[Wfolland]

Have had the same results when opening up throttle while the vehicle is stationary. Guess I'll just assume everything is working as designed, my 10/12's have great top end. Thanks for your input.