carbking

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Everything posted by carbking

  1. Matt - the adjustment part is toward the bottom. Automatic chokes Jon.
  2. No - the raised numbers in the circle are "casting" numbers. Carter (and other carburetor manufacturers) issued specifications for a "blank" casting. Blank meaning no machine work had been done. So possibly Carter had the need for two bowls with 1 inch venturi, one with a 0.020 air bleed, and one with a 0.023 air bleed. The blanks with the 1 inch venturi would be pulled and sent to the machine shop to be machined. The raised numbers on the blanks are referenced, for the most part, ONLY in internal Carter documentation. The casting numbers would be the same, but the parts are different. Different part numbers would be assigned for each item. To illustrate this, I use the Rochester 2-G castings from 1957. The following throttle body castings ALL have the exact same casting number: 1957 Pontiac tripower front (no idle screws, 1/8 pipe tap in rear) 1957 Pontiac tripower center (idle screws, 1/8 pipe tap in rear) 1957 Pontiac tripower rear (no idle screws, no tap) 1957 Oldsmobile tripower rear (no idle screws, 1/4 pipe tap in rear) Jon
  3. A bit of information: Carter stamped the flange number to allow Carter distributors to figure out a rebuilding kit for a Carter carburetor once the tag was removed. Carter metering rods, while generally not common to more than 8~10 different carburetors, ARE NOT UNIQUE! IF the Carter chart shows more than ONE carburetor with a specific flange identification number, absolute identification requires more than checking the flange stamp and metering rods. Remember from Carburetion 101: " A carburetor is a device for MEASURING and mixing fuel and AIR!!!!!" There is always a reason why two carburetors of different tag numbers actually have different tag numbers. Most enthusiasts think about gasoline jets (and metering rods if Carter). What most fail to consider are the air jets, bypasses, restrictors, etc. which will cause totally different metering even if the venturii, gasoline jets, and metering rods are identical. Jon.
  4. Carter codified their part numbers. A prefix of "75" denoted metering rod. Jon.
  5. The holes were one of the methods Rochester used to bleed pressure inside the carb during city traffic. Here is a description of another method: Rochester pressure venting Jon
  6. While most of the vacuum tanks one sees would be Stewart-Warner; another brand of vacuum tanks was Kingston (Byrne, Kingston, and Company). Jon.
  7. Tom - thanks. I remember well the welch plug issue, but did not remember if Buick was involved. Chevrolet certainly was involved. As you are aware, most of the Buick Q-Jets are front inlet. I Haven't owned a 1966 Buick quadrajet in this lifetime (30 years or so) so did not have one to check. If unsure, I try not to post. Jon.
  8. Electric pumps are "pushers" not "pullers". Therefore it needs to be as close to the tank as possible. Lots of folks have done this; maybe someone who has done the modification to a car such as yours will chime in as to which pump they used. Jon.
  9. Most 1968 and all 1969 and newer Quadrajets are stamped vertically on the pump side of the bowl (center section) toward the rear. The number is stamped (recessed) not a casting (raised) number. The number shown in the circle in the picture above is a casting number, and virtually meaningless. Just to complete the run: all 1965 through 1967, and a few 1968 Quadrajets were identified by the round tag pressed into the pump side of the bowl (center section) a little to the front of center. EDIT - Ed (Rivnut) did the 1966 carb have a side fuel inlet? I haven't seen one in years. Jon.
  10. A backup electric fuel pump on a toggle to prime the carburetor is easier than removing either one Jon.
  11. Changing to the paper filter will NOT improve starting after an extended period of time. Many of the speed shops offer an adapter to place modern air cleaners on the smaller necked carburetors. Jon.
  12. The original Compound Carburetion would run without the secondary valve; but one might encounter a hesitation when the linkage kicked in the secondary carb if the RPM was lower than desired. This was the function of the weighted valve. Jon
  13. The Zenith referred to in the speed manual was the 28ADA10. I believe ALL of the type 28ADA10 were 4-bolt mounting flange. At the time, the information stated in the manual was correct; however, I don't think the Zenith would be any better than either well-chosen Carters or Strombergs. The Zenith did have removable venturii, so one could then start with any two carburetors, and if one were a Zenith dealer, one could choose the venturii best-suited to the job. The same may be done by being selective with the choice of either Carter or Stromberg. Both the Carter and Stromberg have fixed venturii in any given carburetor, but multiple venturii sizes in different carburetors. Zenith parts have always been expensive, and today, Zenith parts are EXPENSIVE, as most must be custom-machined. Jon.
  14. Ah, another John Wayne fan! Jon.
  15. I inherited several "monkey wrenches" from my Dad. They were quite useful working on farm equipment when I was a youngster, as we couldn't afford the spanners and sockets in the larger sizes. I have at least a couple of different designs of monkey wrenches. Just Googled the term, and found some folks call a pipe wrench a monkey wrench. However, all of the monkey wrenches I grew up with have smooth jaws. Unfortunately, they aren't very useful in working on most carburetors (too large), although the hammer section of the monkey wrench can be a stress reliever when working with Marvels Since this thread is referencing "legends", please don't start on the Pogue or Fish "carburetors". Jon.
  16. Trini - note phone number in signature. Jon.
  17. Trini - that is the step-up jet assembly. There is a pushrod coming from a hole in the center of a plug in the upper casting that sits on the ball. That pushrod is vacuum controlled. The bottom "plug" is NOT a plug, rather a jet. The jet is available in different orifice sizes, and controls the amount of fuel delivered by the power jet. When the vacuum goes to zero on acceleration, the upper spring pushes the pushrod down, unseating the ball and allowing fuel flow. If the coil spring is fatigued, the power valve will be open constantly, requiring the operator to change the setting for the main metering jet; then the engine would be lean under WOT. The ball, the tiny coil spring, and the much larger coil spring in the top casting are all contained in the better rebuilding kits. We suggest these should always be changed during a carburetor rebuild. Carter BB-1 updraft service Jon
  18. Stumble upon acceleration is not a function of a defective fuel valve. Stumble upon acceleration could be a function of the accelerator pump not functioning, or issues with distributor advance, or??? If the fuel valve is too small, then issues would arise at constant wide open throttle. As far as the design of the Daytona valve, it is my understanding that the Daytona valve is a reincarnation of the Parker Brothers valve. When Paul Parker was still producing this valve, we used maybe 250 or so for BB-1 Carters with gravity feed. Paul made many different unusual valves for us for use with gravity feed, to include Detroit Lubricator (Packard), Johnson (Cadillac), and even some for the mighty Duesenberg model J. We had no problems, other than a couple of customers thought the neopreme disc was a cushion for the float, and installed the valve upside down I have not used any of the valves made by Daytona, we now make our own valves for the unusual applications. EDIT: should be a simple matter to temporarily insert one of the small inline electric fuel pumps for a test. Jon.
  19. Kurt Kelsey Pontiac Parts in Iowa Falls, Iowa for most things older Pontiac. Then & Now Automotive in Boston for ignition, and many other replaceable parts. Factory Pontiac literature And another vote for leaving it stock. Jon.
  20. Strong hesitation at all speeds are indicative of either: carburetor accelerator pump not properly functioning OR distributor advance mechanism not properly functioning. Easy to test either, without buying new parts. Quote Dr. Wehner Von Braun - "One test is worth 1000 expert opinions". Jon.
  21. I probably never obtained an absolute optimal setting When I was still tuning ON THE VEHICLE, A/F gauges were beyond my limited means. And I used a vacuum gauge to check the condition of the engine, not for tuning. For the record, engine vacuum is measured beneath the throttle plate. Changing the curb idle adjustment to eye-crying rich, and closing the throttle plates will give the highest vacuum, but horrible city fuel economy, and city drivability. On a basically stock engine, I would use the stock calibration (engineers do things for a reason). I would pre-set the idle mixture screw(s) and throttle positioner screws BEFORE placing the carb(s) on the intake. I would install the carburetors and fuel lines but no linkage. Then start the engine and run at a fast idle to get the engine to normal temperature. If multiple carbs, would then synchronize the carbs using a manometer; attach the linkage, and set the final idle. For the record, virtually every vehicle I have ever been asked to adjust had the idle adjusted too rich, often eye-crying rich. Once the above was done, would drive the vehicle, paying attention to how the engine felt. Might try changing one calibration at a time (high vacuum, mid-range, low vacuum) +- one step to see how that effected the vehicle performance. With ethanol fuel, I would increase the standard calibration across the board by 5 percent. At the present time, the only vehicle I currently own with multiple carburetion is my shop truck; a 1968 Ford F-100 (exceptionally aerodynamic vehicle ) with 4 speed, approximately 450 HP V-8 running two synchronized 625 CFM Carter AFB carbs. Since this is NOT a stock set-up (Ford used Holleys, and I own no stock in Shell Oil) they are highly modified. Cruising at 70 MPH, the vehicle gets about 22 MPG. I certainly won't complain about that. I do carry a set of four "real gasoline" step-up rods in the glove box, but have not changed them in years. Jon.
  22. If the throttle positioner screw (a.k.a. curb idle screw) is backed out so it is not touching, and the idle mixture control screws are turned in until thumb tight, the engine should stall. They are several "happy medium" combinations of the screws to acquire the desired idle. Jon.
  23. As far as calibrations are concerned, or the individual differences between two different carburetors: With no offense meant, I will not answer that question. WHY? It is VERY time-consuming, and the Carter books with the specification sheets are generally on Ebay. The problem with Ebay is that the specification sheets are loose-leaf, and you have a better chance of winning an argument with the IRS than getting a complete book on Ebay. If one wants a complete book (at higher cost), one should contact that grumpy old hill-billy in Missouri. When many think of carburetor calibration, many think only of gasoline jets, or with Carter, gasoline jets and metering rods. Remember the definition of a carburetor from Carburetion 101 - a carburetor is a device for metering and mixing gasoline AND AIR. If fact, the Carter carbs have: Idle circuit: Idle jet (a.k.a. idle tube), idle bypass, idle restrictor, idle air bleed, and idle discharge orifice Main circuit: Main metering jet, metering rod, vacuum spring, main air bleed. ALL should be considered. Jon.
  24. The larger engine (320) SINGLE carbs has 1 3/16 inch venturi and are 4-bolt flange. So: Compound carburetion carburetors 320 cid 3-bolt with 1 1/16 inch venturii Compound carburetion carburetors 248 cid 3-bolt with 7/8 inch venturii Single carb 320 cid 4-bolt with 1 3/16 inch venturii Single carb 248 cid 3-bolt with 1 1/16 inch venturii Note the venturii for compound carburetion are SMALLER than for a single carburetor for the same size engine. And two fronts from a 248 will work well on a 248; two fronts from a 320 will work well on a 320. The problem in using the fronts is availability and price. The carbs from the engines with single carbs are much more readily available, and significantly cheaper. Jon.
  25. The original Compound Carburetion carbs used on the larger engine (320) were 1 1/16 inch main venturii, which is the same size as the main venturii used on the smaller (248 ) engine with single carb. All of these carbs are three-bolt flange. The original Compound Carburetion carbs used on the smaller engine (248) were 7/8 inch main venturii. Thus, to keep the CFM of the total system the same for the smaller engines when one uses synchronized carbs, one needs to use non-Buick carbs, or use 2 fronts. A few of the Rambler were 3-bolt, most were 4-bolt. For those with machine shop capability, it is NOT at all difficult to machine 3-bolt to 4-bolt adapters. Beginning in 1950, both the smaller and larger engines used 4-bolt flanges. EDIT: Just re-read my post; it should state that these are all Carters, I did not check the Strombergs. Jon.