Weber problem Options

[stock93]

I have a 2.0 type IV engine with 44idfs on it. I was going to sync the carbs today and noticed that even when not pumping the throttle the accelerator pump drips a stream of gas down into the throat of the carb enough that its pooling up a bit on the throttle plate. I'm getting popping back through the carbs. Timing is spot on and the valves are correctly adjusted. I take it this is a problem and they arent supposted to do this? It also smells like its still running to rich. I have 135 mains, 200 airs, 55 idles, 36mm vents, and no velocity stacks currently. Mixture screws are set 1.5 turns out. Its also hesitating from idle to around 3K rpm if I step on it hard like its flooding out. Time to put kits in the carbs? Does the jetting for the accelerator pump need to be changed or adjusted?

John

[blabla914]

I just went through the same thing on a T4 conversion in my bug. Here's what I found.

Either too small idle jet or too small a main jet will cause the hesitation you describe. The hesistation will occur slightly sooner with idle jet too small, but the difference is subtle. I found if I could drive around the hesitation by slipping the clutch off the line, it was the idle jet . The hesitation from the main jet came just a bit later so you'd have to slide the clutch like mad to drive around it.

Keep in mind the "idle jets" only control the fuel flow to the transition ports. The idle of the engine is really controlled solely by the screws. The taper on the idle screws of IDF's makes them really sensitive. Even with 45 idles the difference between light and dark plugs at idle was 1/2 turn. One thing worth checking here is that no one previous has filed the edge fo the plate causing the transition ports to always be uncovered at idle. That will foul plugs for sure. Use the procedure in the Pat Braden weber book to size the idles. Works everytime.

125's made my engine hesitate like crazy. 130's still had a small hesitation, and 135's were just right. 45 idles were too small and 55 idles did not fix the hesitation without the 135 main jet. Here's my engine specs and what I ended up with.

Motor
1911
Stock 1.7 heads
mild cam something like .430x290 forget exact
8.8:1 cr
twin 40 IDF's
135 main
200 air
F11 emulsion tube
50 idle

This setup runs like champ and gets about 27 mpg on the highway in a bug with a .82 4th, 4:12 rear, 205-60-15 rear tire. I drive 80 (that's a clocked 80, not by the speedo) all the time.

There is an alternate setup in the back of the Pat Braden book that uses an F16 emulsion that changes the point that the air correction is functional. I think it uses a 125 main and a 180 air. I'm going to try that next.

I'd be interested to hear about what you find on this engine.

Kelly