I am in the process of getting a freshly rebuilt 2056 up and running.

9590 Raby cam

Dellorto 40 with the CB performance upgrade kit

Is there any consensus are 40's big enough for this engine?

I am having a hard time getting it to idle and come off throttle.

I have the largest idle jets in the carbs and I am still getting popping out of the carbs.

I checked float levels today and they are good.

Waiting on more jet combinations to arrive next week.

Any more thoughts on things to check?

36s should be plenty big enough. If you are running 40s what are your current specs?

In order to properly jet/tune you should really have an afr.

What idle 7 mani jets & venturi's are you running ?

.75 idle
1.65 mail
1.7 air correction jet
.5 pump jet

I think the venturis are 36

just for comparison, my car has DRLA 40s set up with 30mm main venturis, 55 idle jets, 135 main jets, 180 air correction jets, and 9164.2 emulsion tubes. I know these are a little smaller than the factory settings, but they seem to work well with the current engine build (914 2.0L, Elgin 7008-4 cam [280* duration, .332 lobe lift], Mahle Euro PC set [8.0:1]). Car has run great with this set up for almost 100K miles (I made some adjustments for altitude when stationed in Colorado Springs)

What is the CB Performance upgrade kit?

CB Upgrade kit is smaller venturis and different idle jet setup. This I'm told totally changes the jet set up.

What you're running sounds like what I'm told a stock 40 would run.
I might need to go back and change the carbs to the stock configuration.

The upgrade kit for 40 webers gave me larger venturis along with the spray bars and jets. 44 webers have a 34 venturi to start with, and your dells are 36's like mine. Unless you ordered something different.

That is an indication of plugged idle ports/jets. It's a known, common problem with Dells, as the air intake of the idles is on the "floor" of the top.

Pull the idle jets, ensure they're clean, and then blow out the idle ports. Then ensure you have a good clean air cleaner assembly.

This was a common problem in sandrails and such. CB Performance makes a kit that raises the air intake above the floor. I have it, but have only installed the larger venturis:

https://www.cbperformance.com/product-p/7345.htm

I have a strong 2056 race engine (86A cam?) with 40 Dells and we'll be at Lime Rock next weekend. We're gonna spend the weekend jetting/re-jetting. Right now we're at:

CB 36mm venturis
1.80 air correction
1.70 mains
.7 idles
.65 accel

Idle is way too fat, around 11, but full throttle through the power range is good, around 12.7-12.9. After the weekend we'll play with it and see where we end up. Remind me after Labor Day for an update.

Greg

I am not totally sure these carbs are from the guy who rebuilt my engine so I'll have to measure them to be certain

I'm no expert, but I believe your engine will breathe just fine, with an exhaust that will allow it to.

Interesting Not sure how close the 86A cam is but looks like the direction I am heading.

So I am assuming the Id of the barrel in the carb is the venturi and these measure to be 36mm.

These have the raised idle jets. I'll try cleaning the ports as I only cleaned the jets yesterday.

I'll be interested to hear how your Lime Rock weekend goes

It has a set of Tangerine Racing headers so it should be breathing about good as it can.

Pulled the carbs off and sprayed and blew everything out.

Now it at least idles a bit on the low side but better than it was.

I might need to go back and clean the pump jets as it isn't coming off idle very well.

I do get a squeaking or tweeting when accelerating, anyone have any ideas on what this might be?

Dellorto whistle is common, nothing to be concerned about.

Greg

man wish i could make a trip to Lime Rock Never been and would be cool to watch you test and tune.

Any idea what difference 1.8 vs. 1.7 air correction jets will do?

I'll check with you after labor day
?

Larger airs bring in the main sooner. Smaller will bring them in later. What you are looking for is a good balance of brining in the main when the idle circuit drops off. Your idles are way to large. To get the feel of the idle jets take the main stack out and drive the car around. You will know when the mains will kick in as the car will fall on its face. I would go with the base above with 55 idles. Venturi are your powerband. Larger will allow you to still feel power at higher rpms. 28s maybe 30s should be right for that engine.

You need to look @ the venturies ,they have a number on the casting,it should be 28 or possibly up to 32 for your carbs (40 drla) the bore of the carb will be 36mm most likely but that's not the number you are after
Have no experience with this conversion but Dells are very easy to tune,make sure you have a good clean regulated fuel supply @ around 3psi ,good luck.

sample of the number on the venturi.
My 36 weber IDF has 32 venturi and you will see it on this pic.

Click to view attachment

When I have had smaller idle jets in it pops indicating its lean, right?

Just to understand, you are recommending
1.8 air
1.7 main
.65 pump
.55 idle

and change to 28 or 30 venturi if that is not what I have

My venturis don't have the secondary under the butterfly like in your picture.

it is a straight 36mm bore top to bottom

My set up with a 2056cc, 86A, crappy E10 gas, 9.5:1 (to help with E10), lot's of custom crap... It's a pretty fast autocross car for it's displacement.

Dual 40 Dells
36 vents
160 main
180 air
62 idle
35 pump
5-12 floats, vertical
250 inlet valve
30 degrees advance

I've gone through 10 variations on the 36mm venturi, all tuned with an LM-2.

Educate me a little What do you mean by 5-12 float, vertical?
and 250 inlet valve?

mine falls on itself with quick throttle with 35 pump lots of popping if idel jets are smaller than 70.

When setting the float level, holding the carb top vertical (as to not engage the spring on the inlet needle valve) I set it at 5mm. 12mm is the full droop. Inlet valves come in sizes just like jets. I use the biggest one I can get to help keep the carbs from starving and make less work for my fuel pump.

What are your ignition settings? Are you popping out the exhaust or out the carbs? Have you verified that all 4 accelerator pumps are working? Rebuilt the carbs recently (full cleaning and new gaskets including pump diaphram)? What are your idle volume control screws set at (this can be indicative of a lean or rich environment) and how do they "react" to changes?

I think you will be happier using 32mm vents on your 2056. Shoot for a 950rpm idle.

So is the inlet valve the fitting where the fuel lines attach?

Not sure what the timing is
Carbs are in good shape and clean
Pump jets are working
Idle mixture screws don't seem to have a lot of impact on changing which CB Performance told me that is a sign the idle jets are too big, but with smaller jets it pops out the carbs

So when you are holding the carb vertical and you set the 5mm gap are you pushing the the float closed or just letting it rest?

Never mind on the inlet question I see now that is the needle and seat