<VV> Weird carb problem

[Tony Underwood]

At 08:32 PM 1/30/2010, Daniel Monasterio wrote:

>   While tuning my 64 GB 110 PG engine (recent rebuilt), I tried to 
> be very carefull on rebuilding a good pair of 68-69 carbs (64s were 
> too rich at 2500-4000 rpm, even with 48s jets) making a good 
> cleaning, checking all parts, making precise adjustments with float 
> levels at 1.125", # 50 main jets (5,000 ft altitude), both 
> venturies matched and perfectly cleaned, new gaskets, new fuel 
> inlet valves, etc.
>
>   Results: Excelent idling at 14.2 AFR with very low HC and CO 
> exhaust emissions, on both carbs, but, at high rpm (2,000 and up), 
> while the right carb performed real fine, the left bank (dual 
> exhaust) showed high CO emissions. On a visual checking (no air 
> filters) found some driping from the left venturi at over 2,000 rpm.
>
>   Removed both carb tops and checked gas level from top and, it was 
> equal (+/- 0.700") on both carbs. Lowered the left float to 1.180", 
> just to see for any change but, the venturi  continued dripping at 
> high rpm, showing a very low decrease on CO emissions (6.4 to 5.8 
> %). As a reference, the right bank exhaust shows 2.1 % CO. Both 
> venturies are 0.024" idle jet, 0.045" main well air bleed, and 
> 0.075" idle air bleed.
>
>   Other info: 110 engine std. bore, Pertronix I ignition, new Seth 
> wires, 4 psi fuel pressure, viton tipped fuel inlet valves, new 
> 7503 (W8BC) Bosch plugs (slightly hotter than W8AC). Both floats 
> are ok, no leaks and have same weight at 21 grams.
>
>
>
>What could I missed ?.... Help !!!



Time to swap the carbs, left to right, and check things again to find 
out if it's the engine or a carb that is at fault.


Did you hang a vacuum gauge on each side of the engine to make sure 
each carb is equally loaded?    If one carb is doing more "work" than 
the other, it could be passing more air and fuel would spray from its 
venturi cluster earlier than the other carb.   Just a thought...




tony..