Webers stumble at 3000 rpm

[101 Alfa Mike]

As you go to higher fuel levels, there is more risk of going too lean/rich when cornering. Not saying you can't go higher. You can. Confirm your fuel levels by looking into the emulsion tube wells. If you look carefully, you can actually see the difference between the static fuel level and the overflow passage to the venturi.

What idle jets are you running? My sources don't show 1968 Spider jetting as 1968 was a dry year here in the States. If its 50F11s, I would try some 50F8s which are slightly richer toward the upper end of the progression circuit.

Mike R

[VeloceOne]

Hi:
Jets as far as I know, should be the following for a 1750:
Main: 130 (Mine came with 125)
Air Correction: 200
Emulsion Tube: F-9
Idle Jet: 50F8
Starting Jet: 65F5
Needle Valve: 150
Accel. Pump Jet: 35
Accel. Pump Bypass: 60

Regards Ian.

[Cosmo]

Thanks for the figures Ian, they match what I have, including a 130 main and 50F8 idle. I'll set the level at 7.5/14 mm and see how that goes.

How does the needle valve affect the set up? A number of spec sheets list a 200 instead of 150 for the 40DCOE.

[101 Alfa Mike]

Generally, you want the smallest needle valve that is consistent with your needs as that gives the best control of the fuel level. Otoh, if you are making more hp than stock, then larger needle valves may be in order. Try to find the less common 175s. Even those have 36% more flow area than the 150s.

[VeloceOne]

Hi Cosmo:
If you do not have a modified engine, do NOT go to a larger needle valve. 150 works fine even on a stock 2L.
I know the stumble seems to be carb related, but are you sure that your ignition system is in good order? Do all the basics first, an not focus on just one area.
Regards Ian.

Note: My car did come from the factory with 125 main jets.

[Cosmo]

Quote:

Originally Posted by VeloceOne I know the stumble seems to be carb related, but are you sure that your ignition system is in good order?