When discussing multiple carbs for Fords, one can't ignore the six-barrel setups, which were optional on assembly line 390s and 406s in the early '60s. Ford offered a similar over-the-counter arrangement for small-blocks, which Carls has reproduced as well. We didn't test any triple-twos, but believe them to be strong performers. That said, Ford had embraced dual quads by the time it developed really impressive cylinder heads, so the factory six-barrel pieces are of a moderate performance, low-rise design. Both carb configurations use a progressive linkage, meaning you're cruising on just two-barrels until you roll hard into the throttle.
For what it's worth, the 1966 Ford High Performance parts catalog advertised a 12-15 horsepower improvement for the small-block, triple two-barrel Holleys (C4DZ-6B068-B), 25-30hp for a dual-quad Carter kit (C40Z-6B068-E), and 30-35hp for the first dual-quad Holley setup (C6ZZ-6B068-A)--all compared to a production iron four-barrel intake and Autolite carb. When the Trans-Am induction appeared in 1968 catalogs, it was advertised to be worth 45-55 horses "depending on the camshaft your engine utilizes."
Lest we leave a blanket impression that dual quads are better than triple-two-barrels, Mopar undoubtedly knew what they were doing when they simultaneously rode the fence with dual-quad Hemis and Six Pack 340s and 440s at the peak of the muscle era. Its six-barrel manifolds were decidedly high-performance in design, and by all accounts, the results were impressive. Fortunately, today's Ford picks involve some intriguing items never offered back in the day--for example, the Dove FE Tunnel Wedge triple-two intake, a hardcore performance piece which would be absolutely wicked on an early '60s big-block Galaxie!
Randy Dunphy's 331 was in transition during our testing, morphing from a '90s underhood look to something right out of the Total Performance era. Of course, the two-fours are a big part of the transformation, but so are the Holman Moody valve covers, which Dunphy installed during our test. Available brand-new at
www.holmanmoody.com, these covers are a great alternative to some of the more commonly seen vintage-themes. We can't promise clearance on every combination, but can say that the HM units easily cleared the FRPP bolt down roller rockers on this engine, and they come in two versions--street oriented covers seen here ($260), and a competition version with twin comp style breathers ($355).
We're pleased to report that almost every '60s-era Ford engine can be fitted with factory-style dual quads, using readily available brand-new components. While FEs were the only '60s Ford engine to get multiple carbs on the assembly line, FEs and small block multi-carb setups were heavily promoted by Ford through its parts department. The 351W and 429/460 arrived too late on the scene to get similar billing, thus it's interesting that applications for these engines are available today as well. Price Motorsport makes the 351W piece you see here (on right), while Blue Thunder makes the 429/460 application (on left)--both of which are available through Carl's.
10a While comparatively rare...
10a While comparatively rare today, a cadre of dedicated enthusiasts has never stopped playing with dual quads. From top to bottom, Peter Bulcock's stroker Boss 302 street machine...
10b
...Randy Gillis' drag...
10b
...Randy Gillis' drag race 331 fitted with a Trans-Am intake...
10c
...and Drew Alcazar's...
10c
...and Drew Alcazar's '69 Boss 302 vintage racer.
11 4160 series Holleys such...
11 4160 series Holleys such as the 390s and 465s, use a secondary metering plate rather than a secondary metering block with removable jets. If you know what you're doing, the metering plate's fixed jet orifices can be opened up, or alternatively, metering plates are available in several sizes. Blood Enterprises' James Leahy found it necessary to richen the secondary side of the 465s only, and drilled the plate's standard 0.054-inch jets to 0.059. This procedure was done in small increments and retested on the dyno for AFR. The point is if you go too big, you'll need to start over with another metering plate.
12 Leahy always works the...
12 Leahy always works the primary side of the carb for AFR and drivability, before moving to the secondary side. Here, he prepares to open the idle circuit fuel jets on the 465s, since the carbs were going lean immediately off idle. Increasing the orifice from the stock 0.025- to 0.028-inch made a noticeable improvement.
13 Mid-1966 marked the arrival...
13 Mid-1966 marked the arrival of Ford's first Holley flanged dual quad small block intake, which the Blue Thunder is modeled after. This particular catalog entry claims a 40-50 horsepower gain, while others we viewed mentioned 30-35 horsepower for the same combination. Most of these ads were vague as to what the dual quads were being compared to--stock two-barrel or four-barrel? The Shelby parts catalog picked up the Trans-Am intake beginning in 1968, touting its superiority over the original Holley flanged two-4, and promoting use beyond its road race origins.
14 Not every combination will perform as ours did, but we think we've pretty well debunked the idea that dual quads are losers compared to a modern four-barrel. On the contrary, there may be power to gain with the right combination and patient tuning.