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Question on D'ellorto's

1611 Views 9 Replies 5 Participants Last post by  endel
I've got a pair of them on my '73 GTV. What controls or supplies a shot of gas when the throttle is opened up quickly? I ask because when I'm going down the road at speed and I hit the gas, there's a short stumble until the carbs get loaded with fuel again. I know from past experience that on traditional downdraft carbs there was an injector pump that provided that shot of needed gas to compensate for that initial gulp of air when you stab the throttle. Normally it meant a bad gasket in that pump. I have a book on Webers, and is the set-up similar? Thanks
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Yes there is an accelerater pump, but there could be many reasons for the stumble, ie. too much fuel, fuel starvation afterwards, etc.

I wonder if your fuel pump is perfect?, and yes like you say a mini-carb rebuild wouldn't hurt.
If you look down the throats when you open the throttle quickly you should see a little squirt of fuel.
From memory it should only last about 2 seconds, and you adjust it with the spring loaded screw on the pump levers.
I had mine set too long and it would load up too much and cough and splutter till I cleared her out with a few high revs with the clutch in.

No such problems now that I have gone to EFI.
My 74 with Dellorto's from a previous owner, runs fine. I took them apart for a cleaning and carb kit last year and the diaphrams in the bottom of the carbs were stretched and had leaked a little. It seems that every time I thought I had a carb problem, it turned out to be ignition. check your timing, points and condenser along with checking wireing for corrosion.
The car runs great all day long, at all speeds. It runs great under acceleration. It's just that little gulp of air it takes when I quickly step on it.
Webers use a piston inside the carb for an accelerator pump, Dellortos use a lever operated diaphram at the bottom of the carb body. As Brett suggested, have a look in the carb throats. You should see a stream that continues for a second or so after you open the throttle. You may need to set up a flashlight and a mirror to get a clear view down the throat. If you just see a little splutter instead of a steady stream your diaphrams are probably shot or the levers misadjusted. Too much fuel can cause it to stumble as well.

Thanks everyone for the input. Now I know where to look on the carbs. Anyone have an idea where I can get a book or pamphlet on D'ellortos, hopefully with exploded views?
there were several posts on the carbs, I remember one from a vw site, they were popular ad ons for them.
Thanks everyone for the input. Now I know where to look on the carbs. Anyone have an idea where I can get a book or pamphlet on D'ellortos, hopefully with exploded views?
Again as AlfaCliff said PLEASE, PLEASE check thoroughly ignition, valve timing and clearances, etc. FIRST.

My father used to be a carb rebuild specialist as part of his workshop and he used to get rightly pissed with people blaming carbs for problems ... 95% of the time it is something else.

Thus if you do NOT check everything else is perfect first you will make a complete mess once you start adjusting and fiddling. Ofcourse if everything else is perfect then absolutely look at the carb, but I would still BEFORE adjusting remove and clean them out/rebuild and then try again.

Also if your ignition advance process is not working it would give similar symptoms ...

Have fun :).
I owned and raced an Alfa Sud with twin Dellortos and in 8 years of racing I never, ever, ever, ever had to adjust them. All I used to do was clean them every couple of years. Yes my father set them up right at the beginning, but with clean fuel filters AND owners that don't play with them, carbs like these do NOT give problems.
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Yes, I agree. I KNOW how easy it is to make things worse if ya don't take care to make sure the essentials are working right. I agree that once the carbs are set right, they should be good for quite some time. I used to have Webers on the car, which were just fine, never an issue. I had sold the car to a friend, and he's the one who put the D'ellorto's on. They've been really good for a number of years now (since I bought the car back). I've never had to touch them, filters are changed every season. I am very happy with them, so it's not a huge issue... I can roll throttle on and everything is fine. If I stab it, there's a very brief stumble. SO, before I go screwing around with any of that, I will go through everything all have mentioned. It's just the right way.
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