Going In-Depth With Holley's Tri-Power 3x2 Intake And Carburetor Set
Ronny and the Daytonas immortalized the then-new Pontiac’s GTO with the (appropriately titled) song “Little GTO”. The single hit number 4 on the Billboard Hot 100 chart on the 26th of September, 1964 and as a result, it sold over a million copies. Recall the opening lyrics (written by John “Bucky” Wilkin, a.k.a. “Ronny”):
You're really lookin' fine
Three deuces and a four-speed
And a three-eighty-nine
Listen to her tachin' up now
Listen to her whine
C'mon and turn it on, wind it up, blow it out, GTO”
But the GTO wasn’t the only benefactor of those lyrics. It also left an indelible mark on the concept of three deuces. But triple two barrels certainly didn’t begin with the GTO. Oldsmobile had them in the Fifties and so did Cadillac, Chevrolet, Pontiac, Mercury and others. Ford offered them too beginning in 1961. And the truth is, tri power setups were just as common, if not more so in the aftermarket. There were all kinds of them available over-the-speed shop counters for everything from flathead Fords to Chrysler Hemis. But most of those early aftermarket systems were based upon low-CFM carburetors, such as Rochesters and Strombergs. Larger Holley carbs installed later on the tri power Corvettes (340 and 440 Mopars too) were absent in the aftermarket. That’s likely because there were other big fish to fry in the high performance industry – dual fours, tunnel rams, single plane intakes and so on.
But that’s all changed. You see, Holley and sister company Weiand collaborated on a small block Chevy 3x2 setup and it’s a stunner. Of course, the first question is, why would you go to the trouble of adding a three-deuce setup when electronic fuel injection is at the top of the horsepower heap? That’s easy. There’s still a good size cadre of enthusiasts who would rather fiddle with a timing light and a screwdriver to perform a tune up instead of messing with a laptop. Nostalgia called and it reminds us about the simplicity of yesteryear. And besides, who can ignore the wail when the end carbs kicked in on a three-deuce setup? Lastly, many folks simply concur that triple carburetors regularly trump a late model EFI setup in the looks department.
The package Holley and Weiand engineered is a comprehensive three-deuce kit. The package includes an intake manifold, three carburetors, a trio of finned cast air cleaners, and a complete fuel line setup along with a simple staged linkage system. It’s engineered as a straight forward system allowing you to easily install it at home in the comfort of your own shop or driveway.
Designed for a small block Chevy, the intake is a mid-rise, 180-degree dual plane piece manufactured by Weiand. The clever part is the way it’s laid out: it’s designed for three Holley two barrels with secondary metering blocks. That’s no small feat due to the overall length of the carburetors, particularly when you must have room for the distributor in the stock location and still provide for both the water neck and heater hose connections. The truth is, it would have been far easier to incorporate shorter vacuum secondary carbs with metering plates (rather than metering blocks) on both ends. That would have saved a chunk of real estate on the intake manifold, but in the end, Holley and Weiand took a more difficult route in order to package everything to fit. And given the room taken up by the carburetors, it’s not possible to fit a large body HEI on the engine with this setup. It will only work with a conventional small cap distributor...and that probably won’t hurt too many feelings, either.
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:
All three carburetors incorporate a conventional dual feed cathedral style float bowl (the same bowl arrangement found on all Holley high performance carbs). The bowls on each carb are fastened with four screws fitted with late model style nylon sealing washers. The bowl screws are contemporary jobs that allow you to use a 15/16-inch nut driver for removal and assembly. Meanwhile, the fuel inlet on each of the fuel bowls is a standard Holley cathedral bowl arrangement, complete with an integral bronze fuel filter on each bowl inlet.
When it comes to the floats, all three carburetors incorporate a conventional brass layout with 0.110-inch needle and seat setups (adjustable from the outside to allow for external float height changes). The end carburetors are supplied with #70 jets while the center (primary) carb is fitted with #65 jets. The primary carburetor has a 6.5 power valve while the secondary carbs are fitted with power valve block offs. All three carburetors are equipped with 30-cc accelerator pumps (no bulky vacuum secondaries here) and all of them incorporate #31 pump discharge nozzles (shooters). As you can see, the entire setup makes for straightforward tuning.
A fuel line is included with the package, and it’s a vintage style formed hardline complete with a set of brass fuel blocks. It’s easy to assemble and from a vintage point of view, it’s a great look. The throttle linkage follows the same format. It’s laid out around the center carburetor, which is fitted with two female rods right on the linkage. You simply have to hook the linkage rods to the end carburetors using the supplied washers and hairpins. Then it’s a simple matter to adjust the staged linkage so that all three carburetors reach wide-open throttle simultaneously. Then you simply check to ensure the throttles on all three carburetors open and close freely. Once adjusted, tighten the pair of locking nuts on the linkage.
And then there is the dress-up. Holley includes three finned cast aluminum air cleaners, with cast bases and lids. The filter element for each is reusable (it can be cleaned). Holley includes a thick air cleaner base gasket for each carburetor along with a vintage style acorn nut (complete with a built-in gasket and washer) to clamp it down. It’s a slick, nostalgic setup.
When all is said and done, this three-deuce setup is just the ticket for a mild-mannered cool looking hot rod. It’s based upon modern engineering melded with “old school” looks. Best of all, it’s a complete system in a box. You simply need to add intake gaskets and a water neck and you’re done. And when you tach it up, listen to the whine! Ronny and the Daytonas got it right.
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