Is that 290 or 390? If 290, you might be good with a 600 or 650 cfm if just a cruiser or light car. A little more info on purpose might help.
STOLEN FROM INTERNET We’ve all heard the term - bigger is better. We know that more air and fuel equals more power. So why not buy the biggest carburetor out there if this is so? Unfortunately too much carb is a common mistake made that can actually choke the overall performance of your engine. The right idea would be to proportion the carburetor to the engine's volumetric potential (breathing ability). The engine's volumetric efficiency is a measurable value and with a correctly matched carburetor you will receive the best performance possible out of your engine. The formula for calculating how much CFM (cubic feet per minute) an engine requires is: CFM = Cubic Inches x RPM x Volumetric Efficiency ÷ 3456. Any ordinary stock engine will have a volumetric efficiency of about 80%. Most rebuilt street engines with average bolt-ons have a volumetric efficiency of about 85%, while race engines can range from 95% up to 110%. Example: Using a 355 CID engine x 5,500 max rpm = 1,952,500 Take 1,952,500 x .85 = 1,659,625 Then 1,659,625 ÷ 3456 = 480 CFM Even with about a 10% cushion, a 500 CFM carburetor will handle this engine great. If you try this formula yourself, be honest with how much rpm the engine will see. You’d be better off with a carb smaller than needed rather than something oversized that can lead to poor drivablility and performance.
Personally, I would run a Quadrajet. Great driveability with the small primaries, and plenty of volume with the large secondaries. Plenty of good tech out there, both in books and online.
I think you should consider three twos. Rochester 2GCs with progressive linkage work great on my 350 crate. I also have a 700R4. Good throttle response at normal driving, then punch it, the two end carbs and the trans kick down happen at the same time, YAHOO! The 290 hp motor has no trouble handling the three carbs! Thanks for the picture Joker.
A three two barrel with progressive linkage would probably look the best, and with proper tuning, would be great for the street. But I must also say that both the Quadrajet and the Holley 4 barrel carbs would work great as well. Unless a person has modified the Holley to convert to manual secondaries, the secondaries on both brands of 4 barrels open on demand, so if the primary venturi side is properly matched to the engine, you will not be over carburating the engine. In the late 60s and early 70s, there were a lot of guys that thought more was better, and installed a carb where the primaries were too large for the displacement of the engine. This made the car difficult to drive on the street and a lousy performer on the launch. Sometimes, less is more. Bob
I like Quadrajets, but most are 30 years old and tend to wear out throttle shaft bushings( throttle body). You can get kits to fix them, if you feel up to fixing them yourself. Otherwise I would run a 600 Edelbrock or 600 Summit. The Summit is a copy of an Autolite 4100 with annular discharge boosters. Sent from my iPhone using The H.A.M.B. mobile app
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