Carb linkage question 308

Hi,

When standing at the rear bumper of a carb 308, one can see a screw in the center of the two rear carbs for the carb linkage. My mechanic told me that if the linkage is set up properly, this screw can be used to change the idle speed. I was a little hesistant at using this screw because I always thought the two idle speed screws on the left carbs should be used.

Anyway, I might have misunderstood him, but before I get an idiot lesson from him, I thought I would bring it up here. I turned the screw 1/4 a turn - the idle did not increase. Now, after I blip the throttle the car almost wants to stall, then catches and idles smooth again. I turned the screw back to it's original position, but the problem did not go away. How bad did I screw things up?!

Thank You,

Anthony

I would suggest getting a book, like "Weber Carburators, by Pat Braden". ther are others so take your pick. Adjusting the idle is an involved process if you want it to run good. the problem most run into is opening the throttle plates too far on some of the carbs. This moves the carb fro the idle mixture, to the intermediate circut (look into the bore, se he litle holes just above the plate? thats the intermediate circut.Linkage adjusting can be worrysome if the bal ends are worn. I lap them in with valve grinding compound (the linkage part, not the carb. And that really helps et them up accurately.
HTH

Andrew,

if the engine is idleing to low a good place to start looking for problems is Timing first, and plugs second...it is really easy to check timing, requires removing only two small nuts, and everything can be looked at without changing anything. Once you are sure the points (check with a dwell meter) and the timing are spot on....pull the plugs and inspect them, if you find any fouled, replace the plugs, if the engine still idles to low the removal of the Air Cleaner Housing is advised to properly access all the idle jets for a quick cleaning, and access to the mixture and idle speed screws.

If you go into carb tuning yourself use a ColorTune to set mixture and increase the intervals between mixture setting needs & plug changes and use an STE Synchrometer to set balance.

Hi,

My carbs were just synchronized by a mechanic with years of experience (the carbs have also been rebuilt very recently). The timing is spot on (7deg BTDC). The car was not idling very low, just too low when the A/C is on, along with the cooling fans, etc.
I just wanted to bump it up about 100 rpm.

I screwed up and misunderstood my mechanic, I should not have touched the linkage screw (as I suspected). I just should have turned the idle speed screws by equal amounts.

Assuming I have upset just the linkage (as I did not touch anythng else), doesn't this linkage screw just set the position of the throtle plates of the right front and rear carbs?

I turned the screw both ways to see how it would affect the idle - too much counter-clockwise, the car would want to stall after I bliiped the throttle (were the throttle plates being closed too much on the right side carbs because of this?). I found a point where the car now runs as smooth as it did. Now, when I blip the throttle it behaves properly - revs come down, then catch at idle without stalling or bogging of the motor.

I just want to understand what happened and exactly what I did by tampering with this screw.

I will get a synchrometer to see if the carbs are still balanced.

Thank you,

Anthony