Balancing weber 40 IDFs on 1.7 Sprint - Alfa Romeo Forum
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Balancing weber 40 IDFs on 1.7 Sprint

Can anyone tell me whether the Weber 40 IDFs on a 1.7 Sprint engine normally have the air bypass screw holes blanked off because mine are. I've got idle mixture screws, vacuum ports, distributor vacuum advance port but that's it.

I know how to adjust the idle mixture screws to get the lean best idle but then I've got no way of balancing the barrels on each carb.

I haven't tried to adjust or measure anything yet until I know what's going but has anyone got the same and could you point me in the right direction?

Many thanks,

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Re: Balancing weber 40 IDFs on 1.7 Sprint

Have you tried posting your query in the appropriate older models lounge for a response? Worth a try?:
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Re: Balancing weber 40 IDFs on 1.7 Sprint

That sounds like the standard factory set-up. The air bypass screws are covered by tamperproof plugs which you would need to remove in order to make further adjustments. Normally not necessary unless you have changed to hi-flow air filters (I didn't adjust my carbs when I fitted K&N's and I still reckon there's more power than standard) or have had some engine tweaks (new cams, gas-flowed heads etc., although you should be re-jetting for that).

The main issue with balancing (once you have set the optimum idle mixture) is with the throttle balance bar between the carbs. Mine was way out to start with, but I followed the Haynes manual on setting the throttle stop clearances (both sides) to the letter and the difference in throttle response and general smoothness throughout the rev range is dramatic!

So I'd give that a go first before pulling out the plugs and hooking up the vacuum guages. Have fun!

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