Fine Tuning Idle on Weber Carbs
 

I have a newly rebuilt low compression 2.5 motor (66 crank with RS pistons) with the following setup on the 40 Webers - 34 venturies, tall aux venturies, 140 mains, f3 emulsion tubes, 170 air correctors and 55 idle jets. The motor runs great, is very responsive and smooth all the way up through transition - but runs very rich on the idle circuit.
I have tried 50 idle jets and it thens runs badly at idle and transition. Is it possible or worth the trouble of progressively drilling the 50 idles out a little at a time to fine tune the idle circuit?

Robert

Robert:

What cams are you using? :)

E cams and standard 2.7 heads.

Robert

55s should be fine. practice adjusting the mixture screws. in until you hear the idle start to drop, then out until it recovers and runs the fastest/smoothest without going out any more than necessary. keep the idle at around 1100 when you do it, and adjust the speed up or down as necessary as you fine tune the screws. do you have a syncrometer? balancing the airflow so each barrel draws the same amount should be done before any adjustment attempts. you will need to go around several times until each screw, when turned in just a tad, causes the idle to drop a bit. best done in a quiet area and close your eyes and tune in to the sound of the engine when you do it.

I couldn't have said it better,....:)

Thanks guys - will do as you suggest.

Robert