Edelbrock models 1405 versus 1406 carburetors

If you drill the restrictor you will let in more air from the first air bleed leaning the mixture out more. Lightly skim the idle jet. Depending on the engine you may need less drilling. Be very carefull. Try and do it in very small increments. I think 1mm is a good size. But see how you go.

Regards
Billy D...
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