A 340 is a little touchy with a holley 750dp, and easy to flood, but they are the right choice for all out performance. Now you say you like the 600 eddy, I have a 625 carter on mine for about 3 more days. I have raced 340's for many years, and they will take up to an 850cfm dp holley if built correctly. Now there are a four things that you should consider when choosing a carb for a 340
First, anything less than a 750cfm will limit your upper end horsepower somewhat, especially with a single plane intake. If your not shifting it at 6000-6500 every weekend and your running a dual plane intake, then the easier tunability of a smaller carb is for you.
Two, the torque converter plays a major roll in where the power hits. If your lugging the engine down with a stock converter, a big carb isn't going to function as well at lower rpms because the signal to the boosters doesn't get going till its above 2500 or so. When you run a +3000 stall convertor, all the low end stumble tends to go away instantly. So real mild or stock convertor and big carb, not a good mix. UNLESS you go the route I am on Monday with the NEW annular booster venturi style 750dp. This will allow the carb to be sensative enough with the fuel metering to let you lug it all the way down to 2200-2300rpm like a small carb, yet have the big top end charge of the big boys....
Three, the eddy style carbs do not supply enough fuel shot under acceleration to make a 340 happy. A 340 likes a big fuel shot. I have modified enough of the eddy style carbs to know that they idle great, get good milage, have great street manners, and go lean the minuit you lay into it, and then gradually climb out of it as the jets take over. Now if your just running a stock cam and intake, you might not notice it as much, but when you get up into even a mild performance cam, intake, and headers, its noticable compared to the snap of a good running carb.
Forth, to take full advantage of the bigger carb, you need a quick advance distributer on the 340. Without it, it will tend to load up a lot easier, and it will not want as much fuel. I HIGHLY reccomend the quick advance distributer on any 340, stock or modified. It is the single biggest bang for the buck, and is what really lets the big carb work well on the 340. If you ain't running one, I wouldn't bother putting the 750 on it.
Just in case your curious about the carb I went with, its a Quick Fuel Technologies 750DP with annular boosters. It flows well over 800cfm, and its going on my mild 360 with a dual plane air gap, and at present, stock converter, headers, and oooh yah, quick advance distributer set at 39*. The plan is in the very near future to put a new trans in I have, but haven't rebuilt yet with a 3000 converter. When I get this little nasty right, your going to see a mild 1/2 ton pick-up running 11's with a small block and then go cruisen..
