Weber DCOE mystery

[Stevehose]

I have not been able to figure this out, on the front carb of my recent triple weber install the left side main venturi starts to drip at around 2500rpm, well before the other mains tip in (including the right side 1st carb main venturi).

If it were a float issue, it would affect both venturis, yes? Especially since #1 venturi is the higher one because of engine tilt so therefore has a slightly lower float level than the right side.

I swapped the main jets and the float assemblies from another carb just to make sure - no change.

I removed the main jests and observed the fuel in tubes as I revved the engine - the left tube fills up quicker than the right then spills into the venturi tube well before the other.

The vacuum on the left barrel is very close to the right on my Syncrometer - within 1 mark.

The chokes are new and all 32mm

On the DCOE yahoo group someone suggested reversion from a non-closing intake valve - but wouldn't this reduce vacuum in the venturi?

Could it be a semi clogged tube between main jet bore and venturi? Would this create a vacuum imbalance enough to draw the fuel up sooner?

Any ideas from this gruppe of experts?

Thanks

 

[windnsea]

Having done many of these conversions and lived with Weber 45DCOE's for about 40 year now, here's my 2-cents worth:

1. Remove front carb and visually check that both throttle plates (brass) open and close at the same time. One problem with DCOE's is that in time the throttle plate closest to the linkage will not be the same as the other because the brass (or other metallic) throttle linkage rods rotationally torque and create an imbalance between both throttle bores.

2. I'd clean and check all of the throttle air and fuel passages in this carb. Also, check that all air and fuel jets, as well as the mixture jets are correct and passages correct.

3. Put carb back on, check that the fuel level float cutoff valves are doing what they are supposed to do at the right height.

4. Restart the engine, rebalance carbs (and make cylinders 1/2, 3/4 and 5/6 are the same) - this is where a unisyn is handy as the throttle linkage rods periodically twist.

5. If one of the intake valves were grossly not gapped correctly, to the point that there was leakback to the inlet (indicative of major valve gap neglect or another larger problem), well, then that is a larger problem.

Hope that this helps

Windnsea

 

[61porsche]

Accelerator

pump spill symtom. Check it to make sure the ball/ weight is closing as fuel can be sucked into the throat.( It serves the same purpose as the check valve on the Zenith accelerator pump)

Check the carb mounting to see if that one is, "a quarter bubble off." Shift the carb as necessary to the extent possible.

It would be common to see a minor drip. Not constant. Not if it darkens that plug.

 

[Stevehose]

For the record, this was caused by air turbulence from a locked in place 5 blade fan. Upgraded 9 blade with clutch solved it.