650 Double Pump Holley Carb on a 340

[moparnut74]

Hello. I was told this may be too much carb/fuel for a 340 ???? Anyone experiment out there with different carbs...single feeds. I heard Edlebrock 750 single feed was a good choice ??

 

[Avalanche]

I had a 73 Cuda with a 340, bored .30 over with a 650 double pumper and the carb was too big for it. I eventually swapped it out for an 750 with vacuum secondaries and it drove and ran much better.
Its hard to say if its too big for your setup without knowing how the motor is set up.

 

[moparleo]

For the street, all things being stock, The whole purpose for vacuum secondaries is so the carb won't demand more fuel than it has air to burn it. Read " BOG". Also mechanical secondaries need more spark advance to burn the larger mixture.
Now for a properly tuned strip type motor, where you are consistently seeing high RPM'S, the higher engine speed needs that extra shot of fuel in the transition from primary to secondary.

 

[moper]

The douple pump carbs are by desgin meant to be tuned well. They are race carbs. So if you think you will just bolt it on and go, it might work, but it won't work as well as it should. As for "too much"... I don;t think the oldschool 650cfm carbs are too much, but I've always stayed away from douple pump carbs unless the car was a stick with numerically high gearing, or a car that drag raced often and the engine was built a bit. And in those situations they require more tuning skill and time to get dialed in.
So the next question is - what is your car/package now?

 

[Chryco Psycho]

It definatly is not too much carb but if you expect it to go WOT from idle without a bog unless you have a lot of converter & gear it will be tough to tune it out . careful tuning adding enough timing & accelerator pump shot & learning when to go to the floor will make a huge difference , you may have to 1/2 step the throttle until it hits 2500 or so & then dump in the rest . The Holley will outperform the eddy 750 unless you want WOT at idle

 

[moparnut74]

Hello. It's a 340 bored 30 over. Keith Black pistons. I am unsure what Cam is in it ??

 

[moper]

It's rough if you don't know and to me, erring on the side of caution, I wouldn't use a douple pump carb. I don't consider having to phase my pressing of gas pedal as acceptible peformance from a carb but that's just my opinion.