Originally Posted by DoubleVision
the open adapter is junk and the best place for it is the trash. You can screw the idle adjustment all the way in and it has no effect because since the adapter is the open type each cylinder is drawing off the entire mass of the carb, same way at cruise and there on. The adapter also disrupts the fuel and vacuum signal. Best thing to do is install a 4 bbl intake a aftermarket would likely be the best choice since they`ll accept the Holley, a stock 4bbl intake will only accept a Q-jet which will work fine also if you can find one in decent shape. For a stock 350 the 750 is too big but would work if tuned properly. I would just rebuild the 2 bbl carb or go to a 4 intake.
Thanks for the input so far. Concerning the adapters, yes of course they suck, but in my 17 years of using them I've never seen one not work in temporary solutions or even permanent.
So a 3310 ran on a stock 412 chevy... larger engine but interesting since I can barely get below 2000rpm at idle on a 350ci (I looked up the engine block code).
So I'm getting 2000 revs because of "open plenum" mixing due to the carb adapter?? It worked great on a 305 smogger, peanut cam, and 600cfm VS on 4-2BBL adapter. Idle adjust was fine.
Swapping to 4BBL intake, many would say there's not enough cam/CR in the stock 350. True but that's mostly running conditions. I'm talking about idle & the need to know if this carb is a dud. Intake swap alone to stop the open plenum mixing I doubt would drop the 2000rpm idle enough; it's just way to high.
VS carbs are more forgiving when "over-carbing" (during running condition I'm sure). Even tho this case is somewhat extreme, I still think the idle screw should stall this motor with proper working carb idle circuits.
I notice I can lower idle RPM by pressing the throttle back with my hand (and I have "double-return" springs, i.e. stiff pedal, & even unhooked the pedal cable), but it's still not enough, as if the carb is defective and slightly open even at backed out idle (the butterflies looked closed at passing glance before install). This Holley rebuilt carb came with e-choke, that I have unhooked (temporarily) at the air-horn. Before install, I noticed a slight gas odor and traces of teflon tape on fuel bowls. Even "buggered" float level screws. I've seen plenty of Holley remans without this stuff. Did Summit send us a used turkey (not necessarily blaming them, plenty of fine orders there...)? Personally I've seen the same #'s of defective new and reman units (local speed shops also agree here) which is why we ordered the reman to save $50.
Rebuilding the 2BBL (for $16 & some time) can make the car drive for cheap, but I have serious doubt about this 750 Holley now as I feel it should have idled down. Since it was ordered online we need to know if it's good or not (the 377/383 won't be ready for perhaps months). Only "testing" option I can think of is swapping with a known good 3310 from my built 360ci 400hp Camaro (currently in use by wife tho). Perplexed.