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)
Sucp_0708_06_z 406_chevy_small_block Carburetor_dyno_test 2/15

Ignition chores were handled by Mallory HEI distributors feeding juice through a set of 8mm silicone suppression wires.

Thus our dyno comparison had predictable results, this despite the fact that the dual-quad intake in question was the new Edelbrock Dual-Quad RPM Air Gap. A huge step up the performance ladder compared to the original C-26 dual-quad intake, the RPM Air Gap offers larger runners, a taller mounting pad, and the legendary Air-Gap design to cool the intake charge. Equipped with the Performer RPM Air Gap dual-quad intake and matching 500-cfm Edelbrock carbs, Jesse's 406-inch street small-block produced 406 hp at 5300 rpm and 470 lb-ft of torque at 3900 rpm. As expected of the long stroke 400, torque production was impressive from 2500 rpm all the way to 5000 rpm, never dropping below 400 lb-ft of torque. Torque production from the 406 exceeded 450 lb-ft from 2900 rpm to 4600 rpm, making for a sweet (and useable) power curve.

By comparison, Joey's RPM Air Gap and single 750-cfm Edelbrock carb showed why so many small-blocks are currently running around with dual-plane intakes and single four-barrel carbs. His 406 Mouse thumped out over 500 lb-ft of torque, with a peak reading of 505 at 3900 rpm on its way to a peak power number of 444 hp. Torque production from the single-quad motor exceeded 450 lb-ft from 2500 rpm all the way to 5200 rpm. While the single four-barrel intake may not have the look, it sure enough knows how to cook.

Sucp_0708_07_z 406_chevy_small_block Carburetor_dyno_test 3/15

The motors were run on the engine dyno with a Meziere electric water pump and a Pro Street damper.

Is this the definitive answer to the single- vs. dual-quad dilemma? Not hardly, since a small-block reflects an owner's personality. If maximum power were the only criteria, the world would be filled with race motors. This is especially true of induction systems, as even the most mundane small-block pulled from a long-forgotten donor in the wrecking yard will garner its fair share of oohs and aahs once topped with a 6-71 blower, a stack of Weber carbs, or even a dual-quad intake system. Will the wild induction system take over the street and show scene? Not likely, since the single four-barrel offers drivability and (as demonstrated by this comparison) power production that is difficult to match with a multi-carb system.

When it comes to recommendations, the induction choice comes down to the intended application. If your car is destined to live its life a quarter-mile at a time (excuse the "Fast & Furious" quote), then a racy single-plane intake and large double-pumper might be the best choice. If all-out performance isn't a primary concern and you're interested in maximizing fuel mileage, maybe a Q-Jet or even a two-barrel might be the way to go. If street performance is the key, it's hard to beat a single four-barrel on a dual-plane intake like the Performer RPM Air Gap. If the wow factor is a key ingredient, who can argue with a trick dual-quad system?

Sucp_0708_09_z 406_chevy_small_block Carburetor_dyno_test 4/15

The single-quad combo was equipped with a 750-cfm Edelbrock carb. The RPM Air Gap also received the benefit of a 1-inch open carb spacer.

Sucp_0708_10_z 406_chevy_small_block Carburetor_dyno_test 5/15

Run on the Super Flow engine dyno, the single four barrel 406 produced 444 hp and 505 lb-ft of torque.


subscribe to the magazine

get digital get print