Weber 38 DGAS trouble

[strat1960s]

I have noticed that my carb seems to have problems with the idle circuit and the transition between the idle and main circuit. If I put the car in drive and let it idle down the street you can feel it surge then almost die, back and forth, until I get on the gas and move into the main circuit. When I come to a stop light/sign you can feel the motor surge and almost die again and again. I could hold the brake pedal down as far as it goes, but sometimes the car creeps forward on the surges. The car only does this when cold. I have a 195* thermostat, but some mornings the water temp won't go above 175* to 180*. Does anyone know if there is anything in the carb that helps it transition between the idle and main circuits? Once I get the car rolling, and out of the idle circuit, the motor runs very nicely. It's just the lower RPMs. I have the idle set at +/- 1100 while in park and the idle drops to +/- 750 while in gear.
Any suggestions to the cause and solution would be greatly appreciated.
By the way, Happy New Year.

Ted

 

[66200i6]

Surging in any circuit usually is caused by a lean condition. Try increasing the idle jet size. It may take some tuning.

Good luck, Ric

 

[falcon fanatic]

These webers are also sensitive to having the idle speed screw too far in so the butterfly is a bit too open. Make sure you follow the lean best idle setting procedure as precisely as you can. You can download a copy of those instrucions here:
http://www.redlineweber.com/html/Tech/3 ... unning.htm

 

[strat1960s]

The thing is that I was running rich. So if I richen the mixture up any more, I will be back were I started. Remember, my rich condition is supposed to be what prevented the rings from seating after the first rebuild. Now that the motor has been rebuilt a second time, I am not looking forward to a third time.
By the way, it's official, I am deploying to the Middle East. I'll be home for a few more months. When you don't see any more posts from me that would be a good sign I am over there. When you see more posts from me would be a good sign that I'm back.

Ted

 

[66200i6]

Then maybe we can get your rig dialed in before you leave.

Take a look at the position of the throttle plate. The edge of the plate should be just barely clearing the side of the venture. There is a dimension called out in your rebuild info. The ideal position of the plate is the lower face of the plate at the edge next to the bore should meet the lower edge of the upper progression orifice.

If the throttle plate is above this point you are probably trying to idle in the main circuit. That would explain the problems with the transition from idle to cruse and the rich mixture.

Good luck and let us know how its going, Ric.

 

[strat1960s]

I am wandering if my rough idle / transition is due to temperatures? I say this because when the temps are above 50* the car idles much more smoothly while in gear. The motor may stumble once or twice, but the surges are no where as bad as when it is colder. This weekend, I will check out my throttle plate and it position.
Ted