We made sure each test maintained an A/F ratio range within 12.5:1 and 13.1:1. Carburetors also don't produce the same A/F ratio throughout the entire power curve. Because we were using a carburetor, the A/F ratio is subject to significant swings based on manifold design. This meant that Westech dyno guru Steve Brul had to control several variables, the most important of which was A/F ratio. This demanded a very accurate test procedure to achieve best results. With this many intake manifolds, we expected the competition would be very close. Finally, Westech's 134-inch dyno headers and 3-inch Flowmaster mufflers directed the exhaust. Because we didn't expect to exceed 500 hp, we chose a more compatible 750-cfm Holley HP mechanical-secondary carburetor that worked well out of the box, needing only minor jet and air-bleed changes from time to time to ensure the air/fuel (A/F) ratio curve remained between 12.5 and 13.1:1. We also retained the TFS 215cc heads used in the previous test to ensure we could flow enough air to evaluate the intake manifolds and not the cylinder heads. We've retained the same Crane Gold 1.6:1 roller rockers and 0.080-inch-wall pushrods. The engine is basically the same as the one used in the June '13 single plane intake test, with a change to a milder Crane camshaft that is more in line with what would be used in a dual plane intake application. By the time we were done with this test, the 406 had slogged through more than 150 dyno runs with nary a whimper. We've decided to call this engine Rodney Dangerfield because it gets no respect- only abuse. That's our not-so-subtle way to keep you reading Car Craft.Īs we did with our single plane intake comparison, we are using the 406ci small block Chevy first introduced in the May '11 issue ("Build a 400ci Torque Monster For $2,500") and later rebuilt as "Build Big-Hammer Power" in the Dec. A little teaser: If you were to combine the "winners" of these previous tests, you would have a fairly powerful combination-and that's exactly what you can expect us to do in an upcoming issue. Most recently, in our June '13 issue, we completed our massive single-plane comparison ("The Great Intake Flog"), testing 19 intakes on our 406ci small block that is this month's test mule.
The following month, we looked at a bunch of inexpensive four-barrel carburetors ("The Great $299 Carburetor Shootout," Oct. '12 issue ("Eight-Budget-SBC-Head Shootout"), in which we wrestled eight less-than-$1,000 heads on our Slayer 350 small block Chevy.
The first was a budget cylinder head-test in the Sept.
BBC INTAKE MANIFOLD SERIES
We mentioned that this intake comparison is part of a series of small block Chevy components testing we've completed. We bypassed both the Vortec intake and the '87 to mid-'90s intakes, on which the four center-bolt angles were altered. The collection of manifolds could have been even larger, but we limited our test to the'55'86-style bolt pattern. We collected a 23-deep pile of dual plane intakes to continue with our small block Chevy dual plane intake comparison. But it wasn't until we started counting did we realize the incredible variety of choices when it comes to choosing a dual plane intake manifold for a small block Chevy. A well-designed dual plane intake can improve torque, add horsepower, and make that otherwise stock engine look a little more aggressive. If you're a typical car crafter, one of the first performance-engine parts you bought was probably a dual plane intake manifold.
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