DHLA buterflies at idle

[rmorgan12]

I've just had a look at the workshop manual and it seems that the butterflies are all but shut at idle.
Is this right or am I seeing things? A freind at work says he uses a very small drill under the butterflies when setting up at Idle.

[mbell]

Yes they should be almost closed, the idea is to restrict the amount of air fuel mixture being pulled into the engine. Which causes the engine run slowly, aka idle.

Too closed and the engine wont idle, too far open and you'll get a fast idle.

[rgh0]

Yes the butterflies are almost fully shut and the air also comes through the idle mixture circuit and on the DHLA's and later Webers also through the balance screws. They should be closed to the point that the first progression hole is fully covered by the edge of the butterfly at least so it is not exposed to manifold vacuum at idle. This is achieved by adjusting the throttle bypass balance screws.

cheers
Rohan

[rmorgan12]

Thanks to Rohan and mbell for their replies. Has helped me a lot. Have gone through syncronising section in handbook and now I have a car that starts on the button with just a bit of choke.