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Mon Aug 11, 2014 1:40 pm

Hi!

I have 1776 engine with dual DRLA 40 carbs (rebuild Alfa carb), electrical fuel pump (presure is set to 2.5 to 3 psi), SVDA Alfa rebild distributor.
Carbs have this setup 28 venturi 55 idle, 180 air, 115 main.
My problem is to increase the consumption of gasoline lately, another symptom of the black exhaust and black smoke coming out when revving. I tried to change the set up on carbs 53 idle, 112 main then 58 idle and 115 main. I installed a pressure gauge and it is about 2.5 to 3 psi. The result was almost the same, black smoke and high consumption. I have also repeatedly cleaned carburetor float set to 6mm / 12mm.
The new symptom is that the engine speed very slow decline from 2000 to 800 rpm. It is very annoying Mad Mad Mad symptom...
Are they all the associated symptoms? Will I solve problem if I put return line for fuel from carb to the tank? Or this is Dellorto Drip problem? Even I have two sets of the carburetor, with the second set of the situation is similar or the same.

So, any advice will be great!!!
Thanks for help!!!

Thanks for any help

Mon Aug 11, 2014 1:54 pm

Acy,
Look down the carb throats and check to see if fuel is dripping out the aux vents. If this is so, float setting or needle valve is leaking by. If fuel is seeping out the progression holes, it is dell drip and repair is needed.
Slow return to idle could also be result of poor linkage geometry. How do you set your AF mixture screws per cylinder? Do u have the throttle plate shaft nuts on too tight by chance? A return spring would be last option if everything else checks out.