4 Barrel Carburetor Dyno Test - Civil War

Are Two 4-Barrel Carbs Better Than One? We Dyno Test Them To Find Out

Richard Holdener Jun 26, 2007 0 Comment(s)
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Like the single-quad combination, the dual-quad small-block received identical Pro Comp aluminum cylinder heads.

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Rather than the go the single-carb route, Jesse topped off his 400-inch small-block with a trick dual-quad setup. Compared to the original Edelbrock C-26 dual-quad intake, the RPM Air Gap induction system was 1 5/8-inch taller. Hood clearance was not a problem since both motors were destined for home-built rat rods.

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The new RPM Air Gap dual-quad intake offered a significant improvement over the original C-26 intake. Few things look as good as a pair of dual quads, and now Edelbrock has added bite to go with the bark.

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406 Small-Block Edelbrock Performer RPM Air Gap Dual Quad
Who wouldn't be happy with a street engine that pumps out an honest 1 hp per cubic inch, especially when the motor displaces 406ci? Equipped with a set of Pro Comp aluminum heads, a healthy hydraulic roller cam, and the new Edelbrock Performer RPM Air Gap Dual-Quad intake (with 500-cfm carbs), the 406 produced 406 hp and 470 lb-ft of torque. Torque production from the big-inch small-block exceeded 450 lb-ft from 2900 rpm to 4600 rpm. Add to this power production the cool factor that comes only with multiple carburetion and you have an impressive rat rod powerplant.

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406 Small-Block Edelbrock Performer RPM Air Gap Single Quad
This combination clearly demonstrates why dual-plane intakes combined with a single four-barrel carb rule the streets. Equipped with the Edelbrock Performer RPM Air Gap and 750-cfm carb, this 406 produced 444 hp and 505 lb-ft of torque. In all honesty, it is tough to beat the Air Gap for average power production. This combo netted torque reading that exceeded 450 lb-ft from 2500 rpm to 5300 rpm.

And A One, And A Two...
The results of our comparison show the single four-barrel to be the hot setup, however, as the old advertising escape clause goes, "individual results may vary." An Edelbrock spokesman says its testing has shown the two systems used here to be very similar in power output, and that he was surprised by the 39hp deficit we witnessed for the dual quad. In hindsight, maybe we should have swapped induction systems to see if there were any variances in the two 406s. Still, given our compression ratio, cam, and redline, our trusty old carb-picking formula says 750-cfm should be just about ideal for this engine.


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