Weber linkages needed, and Dellorto problems

[X-racer]

Hi all

New member here.

I have a recently acquired '73 Spider with Dellortos. They are in desparate need of some work, so I want to replace them with a pair of 40 DCOEs. I have the carbs, but the linkage pieces on the throttle shafts are mis-matched. The tab on the rear carb linkage is too far from the spindle center to match up with the synchonising adjustment screw and spring loaded plunger on the fromt carb linkage. I have 3 of the front carb pieces, all the same. I'm suspecting that the rear carb linkage piece is incorrect. The front carb piece has the adjustment screw operating tip just about exactly 1" radially from the center of the throttle shaft. The rear carb piece has the tab at least 1/4" further radially from the throttle shaft.

If one of you Weber experts here could take a look at your linkage pieces, and tell me which is correct, I'd appreciate it! If someone actually had the correct pieces and wanted to part with them, it would be even better!


Now- the Dellorto problem. They are 40 mm, with 34mm chokes, on a stock (I hope) 2 liter. They have a HUGE bog as soon as the throttle is cracked open. The engine will literally try to die until the throttle is opened at least 1/4 to 1/3 opening.
The transition passages appear to be clean, and open, the idle mixture volume screws seem to react normally.

I had the carbs off this weekend to check them out. With a full fuel bowl, when the throttle shaft is opened, there is no fuel flow from the pump jet until at least the 1/4 to 1/3 opening, then the pump jets throw an enthusiastic jet of gas a good 3 feet, with quite a bit of duration.

All my experince has been with Webers - almost every car I've owned over the last 30 years has used Webers at one point or another (American iron excepted). I have no idea how to deal with this Dellorto problem - is there some adjustment for the accelerator pump timing? Are the pump diaphagms shot? There appears to be an adjustable nut on the pump operating arm, and the operating lever on the throttle shaft also looks to be adjustable.

Bruce
Seattle
'73 Spider
'78 Spider (Spica)

[papajam]

Welcome, X-racer!

Don't know a thing about Dellortos but if "the pump jets throw an enthusiastic jet of gas a good 3 feet", I'd say the diaphrams (or pistons) are good. It sounds like the pumps are starting too late. In all the carbs I've worked on, the pump moves as soon as the throttle does. It appears you've found two separate adjustments for the pump so perhaps the fix is just a simple adjustment.

I'll check the Weber linkages when I get home and post the findings.

[papajam]

The linkage on this pair of DCOEs, off an Alfa, would appear to confirm that the front linkage you have is correct.

[papajam]

The linkage on the rear carb has approx the same dimension from the throttle shaft.

[papajam]

The ball is about 1.5" from the shaft. Check out www.piercemanifolds.com ;they stock a bunch of Weber stuff.

[X-racer]

Yup. That all looks like it should. The rear piece in your pic is what i need.

I hesitated to order blind from Pierce Manifolds without knowing the dimensions of the linkage piece they show. There obviously are 2 different versions, since mine looks the same but is different dimensions.

How about sending me that nice rusty one in the pics?

[120]

I didn't catch what rpm the motor bogs down at. If it is less than 3 grand try a richer idle jet. If it is more than 3 grand you might try a richer emulsion tube.
I believe your pump is working as intended.

My guess is you have too weak an idle jet(s).

[X-racer]

At no-load idle, you can't even crack the throttle open. If you get real aggressive with the throtlle (into the pump discharge) you can force the engine through the huge bog.

I'm not really too interested in getting the Dellortos running at the moment - I really want to get the Webers on and running since all of my expertise and copious supply of jetting pieces is for them.

[papajam]

How 'bout we do something like this X-racer. I'll send you the one I have (I'll clean it first). That will buy you some time to get another one to send back to me. Will that work?

[X-racer]

That'll work for me. You got PM

[X-racer]

Got the linkage piece, installed carbs tonight.

Without any effort at all - was starting, idling and driving like a new car.

Some jetting work, sync them up better, set the timing now that it will run, and I'm off to chase other issues with the car.

This board is great!

Thanks for the loan of the part, Papajam. Replacement on the way as soon as it hits my doorstep.

[Lanciahf]

Hi Bruce,

Did you ever find the cause of your rough running Dellorotos before you switched to Webers? My GTV with dellorotos behaves like yours. I checked all the passages for blockage and they are clean. I installed new o-rings and accelerator pump diapharms. But that did not help.


Did you install new webers or did you have a used set.

Thanks,
Ralph

[X-racer]

I haven't even looked at the Dell'ortos since I chucked them into a box. The difference with the Webers is night and day. They were a pair of very slightly used 40 DCOE with 32mm chokes. Like I said above, I haven't even tried to modify the jetting yet. The car stars with a couple of shots of accel. pump, no choke needed, and drives well enough to work on other items.

I'm thinking that there are other problems to chase with this - the exhaust runs *very* hot - hot enough to burn my shoe after only a couple of miles of city driving. The ignition timing is correct. The next step is to check cam timing.

Unfortunately, there is a motorcycle restoration project (1972 Triumph T150V Trident) ahead of this, so the Alfa doesn't get much attention at this point.

[papajam]

Quote:

Originally posted by X-racer ...the exhaust runs *very* hot - hot enough to burn my shoe after only a couple of miles of city driving...

[X-racer]

ER- that's not a stupid question

I haven't even looked.