SBC Carb size

Hi, I have a 1968 el camino with a 327 and a powerglide. My question is about the carb size for it. I picked up a set of 194 heads for it (only a few thou miles on them), and a nice aftermarket intake (I’ll have to get the exact one, but this wouldn’t be a stock intake). I am planning on rebuilding with a mild to moderate build (350 hp or so) and a cam to give it a decent low end growl. Right now i’m running a Q-jet 4bbl, what would you say would be the best size? keep what I have or go to a holly or edelbrock? 550? 650? any help would be great.

A 450 or 500 CFM carburetor should be plenty enough for this engine. The Q-jet is a great carburetor and if it were my car I’d leave that carb on there but the Edelbrock Performer series are also great carburetors.

The Edelbrock is about the simplest carb to service and tune on this planet. I’ve got several vehicles with the Edelbrock 600s (one is a bit much with 2 of them maybe, but…) on them and those carbs are great.

If you want to stay with a Q-jet and want a bit more for the flat on the floor thing you might consider a carburetor from an old Cadillac big block (472/500). Those carbs were rated at 750-850 CFM and the small primary bores make them liveable for around town driving. Hope that helps.

A 327 turning 6000 RPM at 100 % volumetric efficiency (which you’ll never ever see) would use about 567 cfm.

It works like this: 327 cubic inches times 6000 RPM divided by 2 (because any given cylinder takes air in only on every other revolution). Divide that number by 1728 ( the number of cubic inches in a cubic foot).

You now have (327 * 6000) / (2 * 1728), which is 1962000 / 3456 and that equals 567.7 cubic feet per minute. In reality you’ll never even need that much, since you’ll never achieve 100% volumetric efficiency.

You can, of course, recalculate this if you plan on spinning this thing faster than 6 grand, but street motors usually only make one attempt at 6000 plus RPM.

The 600 CFM Edlebrock performer would do you very well, all mathmatics aside, practical experience says it is the one. Pulling 350hp out of a 327 would be considered more than just mild. I had a 350 pro built and blueprinted (also 1.94 heads) and it pulled 330hp another 20 would have probably required a compression bump (as it was it sat at 9.1). This engine had a bad drinking habit and really liked the good stuff.