<HR style="COLOR: #666666" SIZE=1> <!-- / icon and title --><!-- message --> I've got 2 Carter Competition Series 500 CFM carbs (real ones) on my DeSoto 291 with a 6-71 blower...everything new/rebuilt. I spaced the carbs tight together on the blower so that I can use a one piece Edelbrock/KN air filter. The carbs are so close together (bases touching) that I can't get a tool between them to adjust the idle mix on the rear carb. The carb linkage is progressive, and the rear will be the primary. In order to fire/break-in the engine, I closed off the idle mix /idle speed screws on the rear (primary) carb and ran just the front...the engine doesn't know the difference. Got it running/idleing fine...3 full turns out on each idle mix screw. Now, my question is, do I set BOTH carbs to the same idle screw setting...3 turns out, shut down the front carb and set just the rear carb to 3 turns out, or set BOTH carbs to 1 1/2 turns (idle mix screws) out? I hope you followed this...I had a hell of a time keeping it straight while typing it. Thanks, guys... <!-- / message --><!-- attachments -->
If you want to balance the idle mix job between the two, you need to split the difference, 1.5 turns out on each. Remember that individual screws have their own flow characteristics. You will need to tweak a bit to get it right. This is the prefered way to go as it does have a very minor effect on running mixture at higher throttle settings since it does represent a small percentage of the fuel introduced in each carb.
Scotty is right. Mine seems to like about 1 1/2 turns out on all four screws with progressive or non-progressive linkage. With my carb linkage progressive, the car had a slight bog leaving stoplights. Changed to non-progressive and she loved it. You might wanna give non-progressive a try when your car is running and driving. See ya, -Abone.
Abone, That makes perfect sense. You're force feeding this thing more than part throttle of a 500 cfm carb when you supercharge. The extra pump shot was poorly placed on a progresive linkage and really needed earlier with the first carb. Put them on a 1:1 set of levers and they really do make a nice pair.
I found that blowers like a lot of idle fuel, i'd set the rear carb on the high side and then use the front carb for tuning. You've got a nice mixing bowl right under those carbs so it won't be overly rich at one particular point, i.e. the rear carb feeding the rear cylinders on a tunnell ram. Make sense?
Don't run a progressive linkage on a blower motor. The bog talked about can lead to a blower "sneeze" and can lead to broken parts if your pop off plate fails. Also I always run Edelbrock high flow needle and seat in my Carter/Edelbrock carbs when on top a blower
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