The intake is laid out in the dual plane format – a layout that’s definitely well suited for street driving. The intake ports aren’t huge – they measure 1.90-inches by 1.15-inches (approximately), making the Weiand intake best suited for street driving with an RPM range up to 5,500 RPM. In terms of overall assembled dimensions, the height at the rear is 12.5-inches from the front sealing surface to the top of the air cleaner nut. Meanwhile, the height at the front works out to 11.5-inches from the front sealing surface to the top of the air cleaner nut.
The intake manifold fits all Chevy production line cylinder heads from 1955-1986 as well as 1987-91 L98 Corvette style cylinder heads (non-EGR). It will also work in concert with aftermarket replacement heads with similar port and flange bolt locations. It should go without saying that the intake is for non-emissions applications. It does, however, come with a heat crossover passage, which helps with drivability. The manifold will not work with an EGR valve, hot air chokes or divorced chokes. Holley notes that the intake will accept a manual choke setup or an electric choke center carburetor (which is included in the kit).
The intake accepts Holley two-barrel carbs with “v” bowls (that’s the cool cathedral style fuel bowl that was the hot setup in the Sixties). These carbs can have a maximum throttle bore size of 1.50-inches. The carb setup is based upon a 325 CFM Holley carb in the middle, flanked by a pair of 350 CFM carburetors. That’s a lot of CFM – 1,025 in total, and in truth, way too much for the intended application of a street-driven small block. But there’s a big caveat: Two-barrel carburetors have their CFM ratings performed at a different pressure drop than similar four-barrel carburetors. Here’s how to figure it out:
An industry standard for carb airflow testing is as follows: A two-barrel carb is tested (for flow) at 3" Hg depression. Four-barrel carburetors are flow rated at 1.5" Hg depression (the two-barrel airflow test is obviously performed at a depression that is double the four-barrel test depression). Flow varies with the square of depression. This means it’s pretty simple to convert from one test depression to the other in order to compare carbs. There are a couple of ways to accomplish this, but the easiest is as follows (this converts two-barrel numbers to four-barrel numbers):
Total CFM divided by 1.414
1025 divided by 1.414 equals 724.9...or, 725 CFM.
This tells us the complete three-deuce setup flows 725 CFM (when compared to 4-barrel numbers) and that’s right on the money for a street driven small block, especially when you take into account the secondary carburetors. Inside, all of the carburetors follow the conventional Holley high performance layout. That translates into simple tuning along with replacement parts that are readily available. Bottom line here is, the three-deuce setup is easy to work on: