"670" is corporate marketing nonsense, by the way. Just sayin'. As has always been, is still, and will always be: 1-1/4" primary & 1-5/16" secondary venturi diameters; and 1-9/16" throttle bores = 600cfm Holley carburetor. Tune accordingly. I've seen and fixed enough dysfunctionally-calibrated street avenger (and other apparently "new and improved") carburetors now for a couple lifetimes, lol
Friendly suggestions for modifications/changes based on experience fixing a number of "670" street avengers that are dysfunctional, and/or oil-diluting, plug-fouling, stupid rich (usually needing to be so far into the primary transfer slots and with higher than necessary idle speeds) in general:
- 0.028" primary idle feed restrictions, for stock/mild application (camshaft), too big... 0.026", better...
EDIT - re-read original post, air gap intake... ^ probably better left at 0.028"...
- 0.026" secondary idle feed restrictions, for any application, too small... ~0.030", better... *
- 0.080" primary idle air bleeds, too big... ~0.070", better...
- 0.045" secondary idle air bleeds, too big... 0.028", better... *
- #68 secondary jets for bigger venturi throats than the primaries (that have #66 jets AND 0.046" power valve channel restrictions) are too small... ~#73 secondary jets, better...
- * always standard fare secondary calibration in the past for with 1-9/16" secondary throttle bores, for a brief and adequately rich secondary transition (since there's no shooter back there), and that allows for trouble free (no flat spots, bog, etc) use of a quicker vacuum secondary spring, like a purple or long yellow... for much better go-baby-go
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