carbking

We have several, from missing parts to complete. Jon.

Very early (1930's) copper was used for the line. Due to the heat transfer properties of copper, it was found to be necessary to place the asbestos cover on the line to insulate the line, retaining the heat. Later, many tubes were made from steel. As the heat transfer of steel is much less than copper, many applications (speaking in generalites here, not for a specific application) did not have the asbestos, but some still retained the asbestos. From a "national showcar" prospective, it would be important to ascertain if the asbestos was used or not. From a "driver" or "local showcar" prospective, bending the line from steel will pretty much eliminate the need for any insulation. Copper or aluminum will require insulation. Jon.

If your car has been retro-fitted with an electric choke, the tube is no longer used; as the electric element supplies the heat to the bimetallic strip. If you still have the hot air choke then the tube may easily be fabricated out of steel line (available at a local autoparts store). The connector that screws onto the choke is also readily available at the same store. Jon.

I can confirm that it is not used on any of the above vehicles. Jon.

Short answer: it probably won't work without MAJOR modifications. Somewhat longer answer: any of the carbs for the W-series cars are somewhat on the pricey side. However, any carb from the same year, make, and engine (even if not a "W") would be infinately closer in calibration than a late 70's or early 80's smog unit. This assuming (not aways a good idea) that the throttle, choke, fuel, air cleaner, etc. would all hook up. The most expensive carburetor anyone will EVER purchase is the incorrect for the application carburetor given to you by your neighbor! Jon.

zondaC12 - set it so it will always allow the choke butterfly to open, and don't start the car if you need a choke . Jon.

zondaC12 - you are probably correct on the Buick, as it is the most common of the 1938 vehicles with a 248, but there are others, and I didn't want to make the assumption. The worst problem with the AAV-1 on the 1938 Buick is the Delco choke. As to the accelerator pump, there may be something wrong with it, but this would not be a factor in a steady speed surge. Jon.

Since you didn't post what car you have, hard to determine which Stromberg; but by 1938 the only original equipment Strombergs which were troublesome were those used by Buick, and only because of the divorced Delco choke Buick insisted on using. Armed with the factory shop manual and a rebuilding kit, a hobbyist should be able to rebuild any 1938 Stromberg. Jon.

Surge is more likely to be a lean condition than a rich condition. Check this by having a friend follow you when you are having the problem. If the problem is a rich condition, he may be unable to see you for the black smoke! Assuming this is not the case; a lean condition may be the result of: (A) Clogged fuel filter ( Clogged tank vent © Defective fuel pump (D) Carburetor needing a clean out and rebuild (E) The use of ethanol gasoline If A, B, and C seem normal, and you are using a 10 percent mixture of ethanol, try readjusting the carburetor float such that the fuel level in the carburetor is raised 1/16 of an inch. If the ethanol mix is worse than 10 percent, recalibration of the carburetor may be necessary. Jon.

As far as I am aware, no one has published a list of Q-Jet numbers and their respective CFM ratings. In fact, Rochester did not publish CFM ratings per se. As has already been mentioned, the pre-1971 Q-Jets are referred to as 750. There were a few (mostly Buicks) from 1971 to 1974 that have a larger primary and are referred to as 800. Most newer (1976-up) Q-Jets are the larger primary (referred to as 800). In 1971, Pontiac, which had been experimenting with the 1000 CFM Carter TQ on the RA V program, had Rochester produce a few of the 750 size but with the outer booster ring removed. These are referred to as 850. This style was dropped after the 1971 model year. Unless one is a carburetion technician with a machine shop, migration of any O.E. carburetor from one application to another can meet with less than the desired results; as the O.E. carburetors are more "application specific" than the aftermarket units. Jon.

Try this link: http://www.thecarburetorshop.com/Troubleshooting.htm#Chokes Jon.

Probably the best single barrel downdraft carburetor to use for this purpose would be one of the Carter model YF carburetors AS USED ON THE FORD 300 CID 6 CYLINDER! Carter made hundreds of different model YF's used on everything from a 134 CID 4 cylinder up to the 300 CID Ford 6. These carburetors differ in internal venturi size. A good rule of thumb is that when migrating any O.E. carburetor from one engine to another; the donor engine and the receiver engine should be within 3 percent of each other in displacement. This can sometimes be fudged slightly if the RPM potential of the two engines is vastly different. The 1929 Buick Master 6 is 310 CID. 3 percent of 310 CID is about 9 CID. Thus the donor engine should be between 301 and 319 CID. The 300 is close enough, as the 300 will turn somewhat higher RPM. I would suggest as early (yearwise) as possible, as the later carbs are calibrated leaner for smog emission. No, we don't have any. Jon.

NTX5467 - you mentioned the vacuum pistons. This is another example of excellent Carter engineering. Carter was aware that wear would be a problem, so the vacuum pistons were deliberately constructed from a "softer" grade of aluminum. The vacuum pistons are "sacrificial" (sp); they wear to protect the main casting from wear. When rebuilding an AFB, it is good practice to replace the vacuum pistons. Jon.

The 4053 was used on the 401/AT. The 4054 was used on the 401/ST. The 4055 was used on the 340/AT. AS A GENERAL RULE! Given the same engine (heads, cam, exhaust, etc.) carburetors for an automatic transmission will be calibrated from 1/2 to 2/3 size richer through all metering circuits than the same carburetor for a manual transmission. This is necessary to compensate for the fluid coupling losses of the converter/transmission; and just one of the reasons it is impossible to obtain the same fuel economy from an automatic transmission as a manual one. As to interchange: A carb for the automatic may be used on a manual vehicle with a slight (but measureable) decrease in fuel economy. A carb for the manual WILL RESULT IN IDLE ISSUES if used on a vehicle with an automatic. Migrating O.E. carburetors across engine sizes (340 -> 401) is not a good idea. In general (unless one is a carburetor technician), a good rule of thumb for migrating O.E. carbs is that the displacement of the receiving engine be within plus or minus 3 percent of the donor engine. Thus 3 percent of 340 is roughly 10 cubic inches; thus the 340 carb could be used on engines from 330 to 350 CID. Specifically, in the question above: the airbleeds are different in the standard vs the automatic carburetors, while the gasoline jets are the same; the same general casting is used, but machined differently. Thus the repair kits ARE the same. A comment concerning another post in this thread: Carter understood that the "coefficient of linear expansion" for aluminum was great compared to the figure for cast iron, and designed the AFB (aluminum four barrel) accordingly. If one looks at the throttle shaft bearing surfaces on the AFB, one will find extended areas in the body, thus much more bearing surface. This additional bearing surface helps throttle shaft stability and the lessening of leaks. Because of the expansion, the design tolerances on the clearance of the throttle shaft to body on the AFB are 0.016 ~ 0.022. Contrast this to the Rochester or Holley which used 0.004 ~ 0.006. A mechanic not familiar with the AFB might suggest that the AFB needed bushing when in fact it would be right in spec. These are some of the most "bullet-proof" carburetors that were ever produced. Jon.

1953. The 7-98 superceded the 7-94 in late 1953 and 1954. Jon.

The year was in the early 1970's; Hershey was blessed with heavy rains Wednesday, Thursday, and Friday. Saturday dawned bright and sunny. We were set up in the flat close to the east gate of the Blue field, and the grounds were somewhat muddy. A young couple came through the east gate: he was dressed in a three-piece suit, she was dressed in something defying description by a male writer. Both had their lower legs covered with the infamous yellow Hershey trash bags. They were pushing a baby carriage with a youngster of maybe 8 months. The baby carriage made about 20 feet before the wheels were completely clogged with mud. The young gentleman was undeterred by this issue. He gazed about, and located a vender with literally tons of old used parts. He found, negotiated for, and purchased a pair of leaf springs, and some wire. He proceded to wire the leaf springs to the wheels and axles of the baby carriage, turned the carriage around, and pulled it like a sled. Absolutely true story. Wish I had a camcorder for documentation! Jon.

The number in question is newer than our books, so cannot give a specific answer. However, the "special" simply meant not a normal GM line. This included Ford in the early 1970's among others, and especially marine applications (Chriscraft, Chrysler, Kiekhaeffer, etc.). These were O.E. applications, not aftermarket. The Carter-built quadrajets were no different in quality than the Rochester-built quadrajets. This "urban legend" is easily understood. Carter charged GM based on the number of units built. There were far fewer "Stage 1 Buicks", "Ram Air Pontiacs", and "W Oldsmobile" cars built than the more common useage, and Carter would have charged more per unit for these items; thus Rochester, after the 1967 model year, built all the high performance units in-house. Those who continually search the core yard, junk yards, swap meets, etc. for items to resell learned this; and thus would not even look at the Carter-built Q-Jets. From this was developed the myth that the Carters were more trouble-prone. Jon.

I had forgotten about the exhaust system on the Triumph Herald. The biggest carburetor problem is ignition; the second biggest carburetor problem is todays fuel. The heat shield may solve your problem. Another possible help would be a return line to the tank (keeps the fuel moving, and reduces the temperature). Jon.

I have read and re-read your response, and finally "a backup electric makes no difference" hit me. I am going to suggest three possibilites (and it will probably be a fourth). (1) Take off the gas cap. Now we know there is no vacuum seal on the tank. (2) Allow the car to idle in the driveway with the radiator partially covered with cardboard. Once the engine gets above normal (but not in the danger) temperature zone, shut off the engine, and move the pistons in the SU carburetors up and down to check for bindage. When dropped, each should hit the bridge making a "thunk" sound (I bet I get comments on this line ). (3) If both of the above don't solve it, replace the electronic ignition and watch the problem disappear. Seriously, there are threads on many chat boards of these things working cold, and ceasing to function well with heat. The comment about the backup pump leads me here. I personally REMOVED the HEI system from my high performance Pontiac and installed a "points and condenser" distributor for reliability and performance. When one reaches my age, one dislikes walking when the electronics fail! Jon.

vepf - the WCFB used on the 317 is significantly smaller than the factory 4-barrels used on the 389. Here is a link of original carburetors used by Pontiac up through the 1960 model year: Pontiac carbs 1926~1960 And 1961~1967 Pontiac carbs 1961~1967 Jon.

Placing too small a carburetor on an engine will generally cause an overrich condition (up to the point where the engine runs out of air); as the velocity of air in the larger engine pulls more fuel out of the fuel wells. Conversely, placing too large a carburetor on an engine can cause a lean condition. Easiest fix is obtain the correct carburetor; however, anytime there is a perceived problem with the carburetor always check the ignition first. Jon.

Carburetors tend to have very little personality. If they work part of the time, they work all of the time (even SU's ). I would tend to look at the ignition, especially if a electronic conversion has been added. Another possibility is the fuel pump and/or fuel filter. Are you still using the Lucas fuel pump? Another possibility (don't laugh, I have seen it happen): have you replaced the fuel tank cap. Some of these vehicles had the tank vent in the cap (not sure about yours). Placing a non-vented cap can cause a vacuum to be pulled on the tank, and fuel will not run out of the tank. Jon.

Steve - thanks. I was afraid that might be the way. Might you know of anyone who will be attending that might be willing to act as a buying agent? I still am looking for some obscure Oakland and Pontiac literature for my library. Jon.

Steve - is this an "in person" auction, or will internet bids be accepted? Jon.

The 1936 used the existing technology Stromberg E series carbs. For 1937, two new carbs were used: the Marvel "B" series, and the Stromberg A series. GM insisted that the Delco autochoke was used with these units. Today, these would be called "Beta" test carburetors. Since these were more-or-less experimental carburetors, the throttle was set up to operate backwards, so they would not be confused with something else. The Stromberg was a fair carburetor with a horrible choke. The Marvel was just horrible. For 1938, the Stromberg was heavily modified, modifications included a vacuum power system. The Marvel was discontinued, and a new C series Marvel used. Again, GM still insisted on the Delco automatic choke. The Stromberg was improved over the 1937 from fair to almost good, with a horrible automatic choke. The Marvel remained just horrible. Both still had the reversed throttle linkage. For 1939, the Stromberg was again heavily modified, Marvel was finally dropped completely, and a new vendor, Carter, was included. GM finally listened to the Stromberg engineers and gave up on the Delco choke. The 1939 Stromberg is an excellent carburetor, as is the 1939 Carter. Since the 1939 carburetors were no longer considered experimental, the throttle linkage returned to normal. Both the Stromberg and the Carter now used an integral hot-air automatic choke. To retrofit a 1939 or newer carburetor on a 1936 requires: (A) A different air cleaner ( Fabrication of throttle linkage © Fabrication of fuel line (D) Fabrication of a "heat stove" to accomodate the automatic choke (see below) To retrofit a 1939 or newer carburetor on a 1937 or 1938 requires: (A), (, ©, and (D) above (E) A throttle arm adapter (F) a cover to cover the exhaust input to the Delco choke To fabricate a "heat stove", do the following: (1) Acquire a piece of steel sheet metal 6 inches by 4 inches (2) Cut a 1/2 inch square from each corner (3) Bend all four sides 90 degrees forming a "pan" 5 inches by 3 inches by 1/2 inch deep (4) Drill a hole in the center of the pan, and install a brass fitting (5) Attach the pan to the exhaust manifold (muffler clamps will work, or be creative) with the "open" side of the pan toward the exhaust manifold. (6) Attach a tube from the fitting in the center of the heat stove to the integral choke on the carburetor. To fabricate the throttle arm adapter for 1937 or 1938 use: Think of a child's seesaw. When one child goes up, the other child goes down. The linkage is the same way. If the linkage "pushes to open", then changing the attachment of the linkage to the other side of the throttle shaft (ON THE SAME SIDE OF THE CARBURETOR) will change the operation from "push" to pull (the throttle shaft is the fulcrum point for the seesaw". Thus machine a flat steel arm with three holes. Use the existing hole in the existing throttle arm for one screw, and bore a new hole in the existing throttle arm for a second screw. Now attach the flat steel arm with 2 screws to the existing throttle arm. The third hole is on the opposite side of the throttle shaft from the first two, and will now serve as the pickup point for the throttle linkage. This hole should be center of the hole to center of the throttle shaft the same distance as the center of the original throttle pickup hole to the center of the throttle shaft. Now - opinion. Quantifying the above carburetors on a scale of 1 awful to 10 wonderful: 1936 Stromberg - 5 1937 Stromberg - 5 (if manual choke is added) 1937 Marvel - 1 1938 Stromberg - 6 (if manual choke is added) 1938 Marvel - 1 1939 Stromberg - 8 1939 Carter - 8 No calibration changes should be necessary on these units, unless the car is frequently driven above 4000 feet, then calibrations for altitude would be necessary. Jon.