OK, Here's my setup;
2.2 (4 cyl) w/ hydraulic lifters and slightly progressive cam for dual dellortos.
Here's what happens;
Car runs great on warm up (warmed up; oil temp about 200 degrees, cyl head temp about 210). Once it is warmed up there is a big flat spot between 2500 & 4000 rpm where anything above 1/2 throttle does nothing but make more noise. My dual carb experience is with old motorcycles (Ducati) and so I have a couple of questions for you experts...
1) Should the feeds (fuel lines) to both carbs be equal length from the "T" after the fuel pump and filter?
2) Since it is an electronic fuel pump should there be a return line back to the tank?
3) On my bikes, I installed nipples in the manifolds for attaching vacuum gauges for syncing. Is that advisable here as well. There are round flat spots on the manifolds that would be the place to do this.
4) Anyone know how to identify which Dellortos I have? Where can I find the part #?
There may be something I have completely missed as well. Any help or abuse would be appreciated! At some point I will probably return the car to FI but that is not an option at this point in time so please don't this inquiry.

1. The lines don't need to be equal length. The floats will regulated how much fuel is in the carb.

2. You can do it either way. Either a internally regulated pump with no return or a return system with separate regulator.

3. They recommend running a line between carbs to equalize, but it's supposed to help idle and low rpm stumble/misfire. I've never found a need for it.

4. You most likely have the DRLA's. 38 or 40 I would guess, it should be stamped on the housing.


It sounds like your idle or main jet is a little rich. 2500-4000 is part of the transition between idle and main, the higher being main jet. I'd lean more to your main jet being wrong. I going through all this jetting fun with my weber 44IDFs.

Thanks Dan. Is there an obvious way to tell if I have a regulated pump or not? I was thinking the same with my main jet being the culprit however, why would that fuel delivery change as the engine got up to operating temp?

There is great probability that the linkage isn't actuating the carbs equally as the throttle increases. I've had a similar problem with Webers...

if your pump is squarish and makes a distinct, loud rattle, it's a facet type. there should be some type of pressure regulator inbetween the pump and the carbs. even a rotory can be unregulated. take a picture of the pump and post it. filter goes upstream of the pump, or should.

k

It's all about the venturis, We need more info. What size venturi? main and air jet?
Idle jet? Did you just buy the carbs and bolt them on? For your engine I would think 32-34 venturis would be max for driveability. Venturi x 4.2 for main jet = 135-145 Mains and 200 air corrections, 55-60 idles. This is a baseline.. Also float bowl levels will determine when the idle jets transition to main jets, I like my float bowls filled up with fuel, Check your float levels. I have run dells and webers and was suprised at how my webers would not run with f-7 emulsion tubes but was like silk with the f-11's. So many factors but I really think you need to start off with the right Venturi size.

Hey thanks Fly....
I've had this unexplainable carb popping on the drivers side I thought was a cloged idle circuit or jet that MAY be bad float level. hmmm. This is 2.0 webcam "street" hydro cam, w/40 idf Webers, 28 vents, 200 airs, 50 idles, and 125 main. I think one side isn't balanced (torque is doa), even though all airflow checks at various throttle points are good.