By Rick Gonser
October 2005. Update 19 Feb 2006 (end of document). Update 27 Mar 2006 (end of document.
Pontiac’s 285 hp dual-quad intake was most likely designed after Chevrolet’s #3731394 intake for the 1956 small block Chevy V8. PMD’s first batch of dual-quad intakes were produced with a developmental casting no. of D-32950. Production castings were identified with casting # 523554 (Part #523550), below.
(There is a picture of the Developmental intake in Pete’s book…)
Since the dual-quad intake was a one-year only offering, the water elbow (or thermostat housing) was unique (Part #522855). Although similar to the 1957 3x2 unit, it was clocked just enough to affect interchangeability, which precludes using the same upper radiator hose.
For the new 2X4 intake, Pontiac initially offered a pair of Rochester 4GC #7009820 (Manual Gearbox) or #7010600 (Hydramatic Transmission) carburetors. Since the carbs had identical RP numbers, both were equipped with thermostatic chokes, as shown on Don Kessler’s 56-2347.
(There are several problems with Don’s set-up, but only a “Guru” (like me) would know)
Pontiac also specified alternate Carter WCFB #2362S carbs, and you had the option of using either a matched pair or individual front and rear units, as shown on this 1956 Corvette (front is different and is not drilled/tapped for a choke assy).
( Chuck, the Corvette King in Valley Circle, gets $3500 for a pair of these. Note that top of front carb is not drilled/tapped)
Both the Carter and Rochester carbs had modest flow ratings of ≈385 CFM, and used straightforward mechanical linkage.
(Pontiac set-ups, regardless of carbs, came with straight linkage, e.g. all four (4) primarys working simultaneously. There is a picture of
this in SERVICE CRAFTSMAN NEWS…)
The infamous “Bat Wing” air cleaner was a thing of beauty. The primary design was borrowed from Cadillac, since the carb spacing was the same on both Cadillac and Pontiac V8s. It consisted of a delta wing housing that used two oil bath air cleaners for filtering. Functionally identical to the Pontiac, the Cadillac unit was painted gold and had a Cadillac “V” emblem in the center.
The Pontiac unit was painted semi-gloss black, and was not punched with ¼-inch holes to secure the chrome Caddy “V” emblem.
(Decals are Chevy items, can also use early Chevy six decals, since the AC wording is the same, only the color differs)
On closer inspection, one finds that a batwing is more complex than it looks. Both of the oil bath cleaners separate from the delta wing, and they can be further disassembled for maintenance. Two spacers are used on the carburetor air horn hold-down studs, so that the delta wing top is not stressed by over tightening.
(This exploded view is the Chevy batwing, but most folk won’t notice, since the pieces are nearly identical to Pontiac/Cadillac. This also shows that the correct length hold-down studs are only threaded on the ends)
Taking a closer look at carbs, it’s obvious that not all early 4bbls were created equal. The Rochester 4GC and the Carter WCFB were available in several configurations, the earliest of which were released in 1952. Although many of the models are similar, there are a lot of subtle differences. Looking down the air horn of an early Rochester 4GC, one immediately notes that there is only one bowl vent per side.
later (and larger) 4GCs have two bowl vents per side.
The Carter WCFB was the world's first four-barrel carburetor. Invented by Carter Carburetor Corporation in St. Louis Missouri, it was introduced to the market in 1952, and was named after the company founder, Will Carter (WCFB stands for Will Carter Four Barrel).
(Clearly shows brass bowl vent upgrade (at $15 ea!)
The Carter WCFB became original equipment on many automobiles of the day. Compared to later four barrels, the WCFB is somewhat archaic in it’s simplistic design. Despite this simplicity, the venerable WCFB is loved by performance enthusiasts and racers alike and is cherished by classic car collectors today.
When comparing venturi’s (or throttle bore sizes), the early carbs had primary and secondary butterflies about the size of a quarter. As the carbs increased in size over the years, the primary butterflies grew to the size of a 50¢ piece, while the secondary butterflies became as large as an old US silver dollar.
PMD #988745 (2O) and #988626 (4O) carb-to-manifold adapters (or wedges), were available over-the-counter, in order to position the carbs precisely for NASCAR and USAC racing on banked tracks.
(This is an aftermarket spacer. OEM spacers/wedges were only .5” thick)
56 Chief’s intake came with 2O wedges & 2nd-design Carter WCFBs, which were apparently found to be much more versatile for racing, than the Rochester 4GCs.
Using McKay Carburetor cleaner and a couple of NAPA #2-5043 kits, the carbs were rebuilt. PMD’s Service Craftsman News addressed a couple of problems with Pontiac WCFBs, e.g. Hard starting on partially warm engines, and Engine stalling on left turns. The first was an easy fix, requiring nothing more than resetting the choke(s) to their indices.
(As soon as you start looking at WCFBs, you’ll see that most of them have the “other” choke. Pontiac WCFBs have the side-entrance choke to clear the Batwing. The center entrance chokes hit the Batwing pass-side oil bath reservoir…)
The second required the installation of a couple of steel bushings, which were permanently installed in the choke vacuum passages of the main body castings. This provided a more positive seal at this point, and prevented fuel from leaking into the passage on left turns, often stalling the engine because the mixture was too rich.
(This should probably say “hard” left. Normal left turns don’t slosh the gas, or lock up the SAF-T-TRAK.
The other fix for “slosh” were the brass bowl vent extensions. These are the gold tubes in the air horn
venturis, which are straddling the hold-down studs)
(For shows, the slide-link is replaced with a straight link and moved up to the top hole on the front carb. Either link is held on with Hurst Shifter circular spring clips) which pull off with your fingernails. If you look sharp, you can see the steel tube spacers covering the hold-downs, which prevent bending the Batwing)
Although originally equipped with straight mechanical linkage from the factory, Chief uses Eelco progressive linkage primarily for cruises. With the factory straight mechanical linkage, gas mileage suffers accordingly, although the car is quite responsive with the air / fuel mixture more evenly distributed to all cylinders. It’s a simple adjustment to switch from progressive to standard.
In case you’re wondering, Batwings are rarely for sale, unless they are part of a complete dual-quad set-up. If memory serves me correctly, the most recent eBAY 285 hp Pontiac 2x4 set-up was snapped up for $5,449 a couple of years ago.
Along with the batwings, it is nearly impossible to obtain any 285 hp parts, as they are hoarded by collectors for speculation. In five (5) years of searching, I have never found a single Rochester 4GC of the correct type offered for sale, even though they were also used on Cadillac El Dorado (Shown below) and Packard Caribbean 2x4 set-ups.
(These 4GCs are 1955 Cad units. Although close, they have different RP numbers and bottom-exit chokes. Note fuel line
between carbs is on the driver’s side, in a Caddy. It can be flipped, and these carbs would work on a Pontiac. However,
being 1st design 4GCs, they perform very poorly at anything other than low speeds)…
The Chevrolet folk have it a little easier as the major Tri-5 supplier, Danchuk Manufacturing, offers a reproduction Batwing for 1956-57 Corvette-engined Chevy passenger cars, which currently lists for only $1,560.
Note that the Chevy delta wing faces the firewall, rather than the radiator, in a dual-quad application. Batwings were not offered in the Corvette because of space limitations. Other major differences include the oil bath reservoir(s) being nearer to the intake manifold centerline, while the carburetor spacing between the carbs is much closer than on the Cadillac or Pontiac 2x4 intakes…
Perusing the 285 hp Heavy-Duty Parts Supplement, there were quite a few goodies available for those with a “proactive” Dealer. An Iskenderian E-2 mechanical lifter camshaft, 3/8” rocker arm studs and nuts, Cadillac steering knuckles, Cadillac wheel hub and front brake assemblies with 9/16” lugs, 15x6½” reinforced Kelsey-Hayes wheels, a high pressure clutch assembly, tach drive distributors, a rear axle housing conversion package (to GM Type 1), shot-peened 28-spline axles with 9/16” diameter studs, and a dozen or so ring and pinion packages from 2.56 to 6.14, with a choice of either a Detroit Locker or the Dana limited-slip unit, etc.
<<<<< Added 19 Feb 2006 >>>>>
This is shot a of # 522855 water neck for the dual quad intake. The water necks are even more scarce than the manifolds, and are almost always missing. You can make one from a 1961-63 Tri-Power water neck, by cutting it at the base, rotating the "clocking" until it resembles this image, then heli-arcing the pieces...
Note the underside of the manifold just below the temperature sending unit. All that cast iron and core plugs are why a special valley cover is required...
<<<<< Added 27 March 2006 >>>>>
This is a 2x4 setup that Jon "The Carb King" Hardgrove restored some years ago. The image is a little over-exposed, but...