Weber carburetor setup

NHGuy

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May 21, 2009
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I am in the middle of this on my engine and I've done a lot of reading on the subject so thought this would be a good reference.
Since the Webers in our boats are direct cast from the same Carters as the Edelbrocks are I think the Edelbrock method is a very good process.
This is adapted from Edelbrock Carb Brochure #0033. Idle Mixture section..
Edelbrock wants you to get highest rpm with each mixture screw starting from a predetermined lowish rpm. Say 700.
Do one side then the other til they equal.
Example: warm engine idle set to 700, turn down mix til it stumbles. back out til smooth and no longer increases engine speed. If it increased more than 40 rpm reset to original rpm. Do the other side the same way.
Now, reset to intended idle. Retrim mix screws again for max rpm only. Reset to correct idle. Turn down mix enough to get a 20 rpm drop. Reset idle to desired value.
This is what Edelbrock calls a lean best idle. Mercruiser does NOT say to do the lean down step. So if your results are poor you may want to add back in the 20 rpm via the mix screws, then retrim the idle speed.
BTW if you have a thunderbolt V this needs to be done with the distributor lock out wire (purple/white) grounded, or the ignition will try to correct rpms on you while adjusting!
 
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