carbking

It is my thought that some may misunderstand the reason(s) for using a flow bench. The major reason was carburetor design, although racing teams may also use them to test modifications (again, design). The carburetor companies, designing carburetors, were interested in very precise measurements of A/F ratios at specific values of vacuum. A secondary function was the CFM available at different values of vacuum, although many look only at WOT CFM. However, CFM figures, at best, are ambiguous. Anyone that believes a carburetor rated 500 CFM will actually flow 500 CFM still believes in the tooth fairy! The engineers did NOT do thousands of tests to determine an exact venturi size and associated air horn and throttle sizes to obtain an exact CFM figure; rather they used standard diameters, measured the CFM, and submitted the results to marketing. Then marketing would assign a CFM value to the carburetor, depending on the needs of the company in the marketing line-up. For years, I have contended the world's foremost expert on CFM was Mark Twain I am unaware of anyone making the statement before Mr. Twain, but he stated "figures don't lie, but liars figure!". Anyone interested in CFM numbers might enjoy this section from my website: CFM ratings What I know of SOME of the carburetor mass rebuilders is that they had very little interest in warranty/returns. They had agreements with their distributors that a certain percentage of sales were going to be returns, and the distributors "ate" those issues. The units were not returned to the company. Trying to "prove" each unit, would be expensive, raising their "rebuilt" prices above new prices. Basically, the flow bench is more of a laboratory tool for design, than a practical service tool. Jon.

OK - Holley used a fluid called Stoddard Solvent, which has the exact same specific gravity as gasoline. Jon.

While I have never used 3D printing, it seems to be a tool to maybe simplify production of a part. BUT The financial successful production of a part depends in a large part on demand. As an example: I have a set of new old stock air valve springs for the Packard (Detroit Lubricator) carburetor used on a decade of Packards up to spring 1929. 40 years ago, I sent the samples to a "Mom n Pop" spring winding company and had 100 sets made to put in the rebuilding kits for those Packard carbs. It took 38 years to go through 100 sets. Now the "Mom and Pop" company has been inherited by the children who now want a 2500 piece minimum. Even if I could still get the 100 minimum, I would not redo these parts at my age. To the OP - I wish you luck; however keep in mind the comments by others about quality. Somewhere the buck must stop. If one does not care about quality, "stuff" can easily be made in a country far away. And there are some who look only at the bottom line. Jon.

Difficult to be certain from the picture, but the downdraft carburetor appears to be a Rochester type B, introduced in 1950. Jon.

The carburetor and fuel pump rebuilding and testing station on my site had testing procedures and tools for service (volume, fuel leaks, vacuum leaks, etc.). The carburetor companies testing with the wet flow bench did NOT use fuel (dangerous). There is another non-flamable material (no, I do not remember its name) with properties (other than the ability to burn) simiilar to gasoline that is used with the wet flow bench. I have custody of the Carter Carburetor Company flow test files. Lots of folks consider "flow testing" as to determine the CFM of the carburetor; but for the most part, Carter was interested in the volume of liquid and air used at a specific vacuum point from which an air/fuel mixture could be determined. Jon

Are you located in Canada finding 94 octane? Remember, the octane ratings scales used in Canada differ from those in the USA. The posted Canadian rating for the exact same fuel will be several points higher than the posted US rating. Jon.

Pictures in my "virtual carburetor museum": Hygrade carburetor and fuel pump repair and test station Jon.

The pressure build-up is due to expansion of fuel in the fuel line between the regulator and the carburetor. I have been suggesting the use of the return line for 30 years. I didn't invent the idea, just looked at what the manufacturers did 50 plus years ago on vehicles with big engines and air conditioning. The factory engineers were not dummies. Often a good idea to see how they solved a problem, and see if their solution may be migrated to a similar problem. Jon.

I have no first hand experience, other than personally never needing to do so, thus - no comment. Jon

Dynaflash - if you stop for gas (or any time you restart the engine when the engine is hot), run the engine at a fast idle (1500~1800 RPM) for 30~45 seconds BEFORE you put it in gear. You are experiencing "hot soak". Once you clear the fumes in the air cleaner, and the puddles in the intake manifold, the engine should run as it did before you shut it off. Jon.

If you are truly concerned about the long time damage: These are NOT rare carburetors, as the Riv used the same carb as other 455's (7043240). Pick up one (or more), rebuild it/them (I happen to know of an excellent source for ethanol-friendly rebuild kits ), and put them on the shelf for the future. Change the soft fuel hose(s) every five years. Drive and enjoy the vehicle. Jon.

Ethanol and higher octane BOTH matter, to a certain extent. Ethanol has less energy than gasoline, so might require carburetor recalibration. It DOES effect non-leather accelerator pumps, as well as soft fuel lines in vehicles not frequently driven. Over a long time (25~30 years or so), it can cause damage to aluminum or zinc alloy carburetor bodies. Repeat, this is a LONG-TERM effect. Too high octane fuel will not completely burn in an engine designed for lower octane, without timing and possibly (depending on the compression ration) compression changes. So, if your engine is not specifically designed for the higher octane; you get worse performance, lower fuel economy, and pay more at the pump for the privilege of lowering your performance! Jon.

Additional information: The gasket posted by KongaMan is for a square-bore, but the heat channel in this gasket is the same heat channel used by Buick on the 1967 430. Note the difference in the heat channel in this gasket versus the pictured Corvette gasket. The gasket itself, obviously, is different. Jon.

Additional information by the OP would have been useful, but since not present, will "scattergun" this post: Four different "original" Rochester quadrajet (Q-Jet) carburetors might be found today on a 1967 430 Buick: 7027240 (early production - Federal cars) 7027241 (California cars) (all you folks that believe the "odd last number = standard transmission" - take note of this number) 7027248 (late production - Federal cars) 7041305 (service replacement carburetor produced first in 1971) ALL of these carbs were specified to use flange gasket 1378509. 1378509 was a thin metal plate with asbestos fibers affixed to the plate. The heat channel looks like the gasket pictured by KongaMan, but the interior of the gasket is completely open, there is no division between the various ports. Because of the asbestos, new gaskets will NOT be of the same construction. One might find a new old stock gasket, or maybe not. I mention the various carburetor numbers one would EXPECT to find because of customers (or potential customers) calling us for rebuilding kits, AN AVERAGE OF 65 PERCENT HAVE A NON-ORIGINAL CARBURETOR! As an aside, this is the major reason we do NOT sell rebuilding kits by application only. If a non-original carburetor is present, then the gasket to the carburetor SHOULD be the exact gasket specified by the manufactured for THAT carburetor. Rochester did not specify the part number for the heat baffle, and I don't have a Buick parts book, so cannot post that number. There are a very few heat baffles being reproduced. One needs to KNOW what the original looks like when purchasing these, as they are often over-sold by unscrupulous vendors. Carter did specify part numbers for these, and there are almost 200 DIFFERENT for Carter carburetors. And without totally beating the dead horse, research would be much easier if more information were presented. Jon

As far as the carburetor is concerned: Find the gauge, and set the carburetor to standard setting; then, and only then, you have a repeatable baseline. Until then, you are guessing! The white tailpipe that was once a sign of a well-tuned engine...............................was lead residue! The tailpipes on my OT newer factory fi vehicles are brown/black in color. Fuel economy is definitely NOT all carburetor. Here is an article I did a few years ago: http://www.thecarburetorshop.com/Troubleshooting.htm#Fueleconomy Others may chime in as to what one should expect for fuel economy on a 1939 LaSalle Jon.

My first thought is to test the ignition switch. It may be making contact in the "start" position, but not in the "run" position. Jon

NOT cold starts? There is no heat when the engine is cold Not going to help starting. The ports are there for driveability in cold weather or cool humid weather. And as far as plugging the holes in the intake are concerned: I KNOW we are talking about Buicks on a Buick forum, but folks get here by using "search" as well as just reading the forum. Lots of folks think of blocking the entire crossover, not just the holes. Some gasket manufacturers actually supply intake manifold gasket to block the entire crossover. So just wanting to nail this down to a specific point. Block the holes under the carburetor, but don't even consider the possibility of thinking about blocking the crossover UNLESS you have a trailered racecar (good for about 1 1/2 percent increase in power at WOT). Since I rebuilt my first carburetor on my own car in 1959, I have made two MAJOR mistakes on my own automobiles: the first was thinking I was smart enough to get some decent HP out of a Pontiac 301 by using a turbo, the second was listening to the internet, and blocking the crossover on a Pontiac 350. At my age, even with a manual transmission, the car simply was not driveable for the first 20 minutes or so after starting around town (my "heel and toe" skills have deteriorated ). I finally solved the problem with a carburetor with manual choke. Oh, and the Pontiac 301? Turns out it wasn't low power. The power and torque are good from 2800 RPM to 2900 RPM. What is needed is a 28 speed transmission to keep the engine in its torque curve! Know this post was verbose; but I felt it necessary to emphasize to block the holes under the carb, but not the crossover. Jon

Joe - great testing! I believe you will find the missing heat shield to shield the carburetor bowl is the culprit. I have not seen this particular one, but generally, these were simply a portion of a sheet metal "box" that would surround the carburetor bowl with maybe a 1/4 inch air gap from shield to bowl. The lower end of the box would have an extension that generally had a hole that fit over one of the carburetor mounting bolts, and could thus be installed with the carburetor. Jon.

Check this link to the troubleshooting section of my website: Fuel leak at throttle shaft when hot Jon

"High octane (99 and 101) unleaded E10 is readily available near me." If this is U.S. octane, way too high for a '73 Riv. If Canadian octane, do a search on RON, MON, and AKI. I'm with Matt on driving more, and keeping fresh fuel in the carburetor. If one will start one's vehicle once a week, and move it at least twice the circumference of a tire, one will have far fewer service issues. I don't agree that non-leather accelerator pumps are ethanol-resistant UNLESS one does drive sufficiently often to always keep fuel in the carb. If allowed to dry out, they tend to become brittle, and crack (fail) with use. And modern floats can be a problem. A used 50 year-old original that tests good (opinion) is superior to the foam floats, and especially the brass floats made on the other side of the world. Ethanol eats the material they use to replace solder. Jon.

Carburetor alternatives? There are quite a few Carter type AFB, and Rochester 4-GC four barrels, depending on the year. There is also a Rochester 2-barrel available. If you are looking for a new shiny carburetor that you can order from one of the online vendors, that doesn't require major butchery to work well on the Buick; I am unaware of a single one. Jon.

It really isn't difficult to make the e-clone function in a Buick. All you have to do is remove the nailhead and transmission, and install a small block Chevy with a TH400. Now you can install the e-clone Jon

Don't even think about the possibility of considering trying to weld that zinc alloy! Yes, I know there are special rods; yes, I know there are folks that claim they can weld this stuff. We had some junk pot metal carburetor parts from this era for test purposes. We tried the special rods. We also tried a number of the folks that claimed to be able to weld pot metal. For the stuff we tried to fix, and the stuff "fixed" by the "experts" we subjected to an artificial heating/cooling cycle test (similar to the heating/cooling of an engine component). ALL failed within a few weeks, cracking at the edge of the "fix". This carb is NOT going to be easy to find, and no, I don't have one, not grinding my axe. But do not allow the scarcity of the part to get you in trouble with a weld. Jon.

Turn the carburetor upside down, and you will see the "hole" is a fresh air intake for the starter switch. Jon.

The only two recommendations that I have would be: (1) internal bypass (2) range that can be adjusted for the maximum pressure for which the carburetor is designed. Jon.