Help me; I got a brain storm question: On a 350 Buick, most people keep saying: use a Rochester Q- jet. 750 or 800cfm right? How com in boot my Holley and Rochester books, they use same kind of diagram when you select carb seize and none of them comes close to 650cfm using 350ci and 5500 rpm? Is it so, that the mass-produced Q-jet fits the application due to the fact the secondaries just dont open more than the engine can handle? (optimizing cfm flow) Or am I fumbling blind on the dark side of the moon here? o No: Lars :Comp:
Car Craft or Hot Rod magazine did a test using that formula for carb size a bit ago, and they found that formula doesnt work for all engines. Like grant455gs said, Buicks have a high velocity port design. I think its sorta like people saying that 4" and larger cylinder bores are the "magic" size for performance, but if you look at the LS1 motor, its a great engine, but alot of the design features are eerily similar to the 350 Buick, like the bore, its only 3.9" and the new Chrysler Hemi is also under 4". The LS1 intake ports are tall and narrow, like the Buicks, and it also has a deep skirt block like the 350 Buick. If they ever come out with aluminum heads for the 350, with all the new head flow and combustion chamber technology, I know the 350 Buick will be a serious contender in the small block arena. Mark
Storm in a cup? Butt with VE 100% 350ci cant be more than 350ci, can it? Never the less, there must be something in what you boys just sad, my 350Buick handles far too soft sec. spring (Holley) compared to them Chevys and Fords that is written about in the Holley book. I got a 750 Rochester Q-jet laying around here, I will try it out, Need some jetting guidance! I got a Crane cam part no: 710571_H-218/280-25-12 dual exh. except that as good as stock. (former chebby carb. dont tell.......) Jetting Suggestions? Lars
This is an interesting topic I've wondered if carb cfm is also effected by length of the engines stroke. Where the Buick 350 has a relatively long stroke compared to its bore diameter, does it need a longer column of air/fuel vapor to performe efficiently?
Let's see...keeping in mind that I am NOT a math major...That's 350 cubic inches in one complete combustion cycle, which takes two revolutions. At 6000rpm (crazy revs) and 100% VE, you'll supposedly be moving (350ci / 1728 cubic inches per cubic foot) X 3000 combustion cycles. That's 607.63888 cfm, way less than your basic 750cfm Q-jet. Seems like we're nuts, right? But, as mentioned above: Buicks don't fit the "average", Q-jets are marvelous things that meter according to engine need, Buicks use the above-mentioned high velocity ports, and then the 350 is a long-stroke engine, which likes free-breathing. Anybody ever actually measure the cfm being used by a Buick engine at work? It'd be interesting to see...
