A recent post over at CO about the w-43 'Hemi' brought up something I have thought about in the past. All the GM branches have there fair share of experimental engines. And a good number of there hard parts are out there and accounted for. Such as Buick 4 bolt blocks. The w-43 Olds. X castings on Chevy stuff and others I remember reading about. Does anyone happen to know if there are any experimental or prototype Quadrajets out there? Would there be any record of super low number of available Quad numbers? As in the ol' 1 of 201 like the Holleys for a z16 Chevelle.
I don't think there were any experimental Quadrajets. The rarest ones out there were made for one year, for the big block 1971 Pontiac HO 455 engines. 7041267, 7041268, 7041270, 7041273, and 7041263. These carburetors were missing the outside velocity booster rings. That significantly increased the air flow capacity at the expense of low speed throttle response. They are very rare, and sought after by the Pontiac crowd. Above information from the Cliff Ruggles book. https://www.amazon.com/Rebuild-Modify-Rochester-Quadrajet-Carburetors/dp/1932494189
There were some pretty rare Q-jets produced like the 455 HO carbs and those that ended up on the Ford 429 Cobra Jet engines. They were factory "hot-rod" carburetors with special features that were not found on any other units. Over the years I've obtained a few factory "test" carburetors. You could see where the factory was plugging off holes, like the lower IAB's for example and moving them up and down in the main casting, most likely testing them after each modification. When working with the Quadrajet one must realize that each specific part number was produced and calibrated EXACTLY for the engine it ended up on. So when you are out there looking for a replacement carburetor and your engine is still stock (pretty rare) the best carb will be correct part number for it. Also realize that when you swap parts around and don't use one from the same part number it may not work well, or at least as good as it should. Even though the replacement part may look correct, and fit, there are often minor differences in them that you can't see or don't realize are there.........
Cliff, are you sure those were factory “test” carbs on not some civilian doing some experimenting? I’ve mentioned this before, but Rochester Products produced what they called “sample” carbs. They were basically prototype carbs for an application that were built and sent to at least the Proving Grounds in Milford, MI as well as the Tech Center in Warren, MI. If they met the criteria of the carline, then they went into production. If not, revisions were made. Us engineering students from General Motors Institute in Flint co-oping at RPD were cheap labor, and they sent us one at a time in a new Suburban loaded with as many carbs that would fit, to deliver them from the Lexington Ave plant in Rochester NY, and get tours of the facilities while we were there. I don’t recall if any of those carbs had part numbers, and anything “prototype” was supposed to be destroyed after testing for liability reasons. Who knows if any escaped?
Oh man, I hate it when you smart people write all kinds of really cool things that I enjoy reading, and then the thread just ends. I hope someone comes up with more new thoughts.
Cliff, are you sure those were factory “test” carbs on not some civilian doing some experimenting? The few that I've seen would not have been civilians, the modifications were too precise and in areas most folks wouldn't be playing around in anyhow. I remember one in particular where they had moved the locations of the lower IAB's further up in the casting and very carefully plugging off the lower ones. I can see a "builder" experimenting with hole sizes, but not location or distance above the throttle plates. Plus how would you be able to test your results? I'd also add that airbleeds are a WAY bigger deal than folks realize. They have a far more dramatic impact on fuel delivery to the engine that metering area, for example. Same with other types of carbs as well. I see folks making jet and metering rods changes, sometimes pretty dramatic ones to increase fuel delivery when they could have simply downsized a pair of air bleeds slightly instead. I've spent decades testing in those areas but don't discuss it much in open Forum. I also pay close attention to what the factory did on specific carburetors used on "high performance" applications. As with most other things with this hobby they were at the forefront and damned good at it. Take camshaft design for example. I've spent the dyno time/funds and tested camshafts back to back, something that few if any reading this will have done. Not going to go into great detail but I'll put up one specific example as food for thought. We had one of my 455's on the dyno to make a cam change. I had been using a factory RAIV cam, 308/320, 231/240, 113LSA. It's not a "mild" cam by any stretch of the imagination and designed by the engineers at GM in 1968 for the "special" RAII 400 engines going into the Firebirds and that engine would use their "new" round port cylinder heads. For the test I purchased a custom cam from Comp Cams. It sported more .050" duration at 240/248 and .060" more lift, advertised duration was 284/296. At that time the lobes I used were dubbed their "best flat lobes". EVERYONE involved with the testing fully expected the "modern" profile cam to easily outrun the "old" factory cam. Well, it was DOWN 10hp/22ft lbs torque and moving it all over the place (ICL) only resulted in loosing more power. It also quit at 5200rpm's where the RAIV cam made peak power at 5600rpms. Another thing that the "bigger" cam did was improve vacuum at idle by 2". I should have known right then and there the engine was going to see it as a smaller cam and that the improved .050", .200" and more lift wasn't going to make up the lost ground in how much time the valves were off the seats. We are told (by all the cam manufacturers, guru's on Forums, engine "builders", speed and machine shop owners, all the experts at car cruises and even your wife's boyfriend) that these "modern" camshafts with their much faster ramp profiles make MORE power than the old antiquated designs with tons of seat timing, gentle ramps and not all that much lift. The testing above was an early lesson for me in the "propaganda" associated with aftermarket parts. The folks making them only have to tell us that they will outrun factory parts, doesn't have to be true, but for sure IF you put results like this on Forum's very quickly someone will get their panties all wadded up and the bashing starts, all the "drama" starts, but in not one single instance will the person doing all the bad mouthing will have a single test result from their own portfolio.........so for the most part I stay pretty quiet about it. The SAME thing applies to carburetors, distributors, intake manifolds, and many other parts frequently used to replace "stock" parts. Since I got into this hobby way back in the mid-1970's I've watched folks "bash" factory carburetors and toss them in the dumpster replacing them with aftermarket carburetors which more times than not only resulted in making no more if not less power, and increasing fuel consumption. Hey, when gas was 30 cents a gallon who cared if you sucked down tons of it, it was cooler to have the Holley stickers in your window and to burn everyone's eyes who stood behind the car in the high school parking lot after a ball game! I'd like to have a nickel for every factory Q-jet that was replaced by an 1850 Holley 600cfm vacuum secondary carb at 600cfm where the owner was convinced that it was going to make more power someplace. About all they ended up with was a cut fuel line/rubber hose/clamps (fire hazard), "cobbling to hook up the linkage, not enough vacuum ports (out come screws and golf tee's) and an adapter plate to screw up distribution and airflow into the intake plenum areas. Even worse many had to "cobble" up excellent factory Ram Air, Cowl Induction, and Shaker assemblies to get the hood closed! OK, I'll sit down now.........Cliff
I thought someone on the board bought a huge hoard of quadrajets and they had some engineering carbs in the lot. If someone does a search you should find that thread. Duane
I remember the discussion, could be the same source that sent one here. I remember one of the experimental carburetors that was sent here came from Texas. It was a a 68 or 69 Pontiac manual transmission carb, pretty sure it ended in "265". Someone had blocked and moved some of the bleed holes, and used a fine tip magic market to make abbreviated notes on it. The story I got with the carb is that it was in a big "lot" of carburetors that came from someone who was employed by Rochester back in those days, kept in storage for decades then offered for sale after they passed, or something like that. It was also mentioned that these experimental carbs never had fuel thru them, just used for some type of flow testing Rochester did at the factory back then.......
The oddest quadrajet application had the be the European inline OHC 6 '76 BMW 525 and 528 . My '75 525 had twin Zenith 2 bbl. carbs that where great carburetors, but a little complicated, and at times weren't very idle friendly.
As of this posting, it's the thread right below this thread... https://www.v8buick.com/index.php?threads/quadrajets-found-a-few-stickers.337787/ Rochester Products wet-flowed carbs using stoddard solvent (similar properties to gas at the time, but less volatile). Up until close to the very end of carburetor production (mid-80's), the entire aresenal of flow benches were in a very large room that was climate controlled - temp, baro and humidity. All personel and carbs passed through a large, double-doored chamber (maybe 40'x40'x20'???) that had huge, sliding doors. One door was the entrance from the plant, and directly opposite was another door that entered the flow room. Once both doors were closed (only one could open at a time), then the pressure was equallized and depending on the baro on any particular day, your ears could pop pretty good. Near the end of carb production and the subsequent flow testing, they did away with the climate controls in favor of a computer program which would compensate for the conditions of any particaler day. If you have the old Doug Roe carburetor book, there are some pictures of the flow room. All carbs were wet flowed, no matter if it was a Qjet, Monojet, feedback, Dual Jet, Varijet etc. The flow benches were all computer controller, at least during the 80's when I was there. And speaking of the Varijet, the engineers in Product Engineering loved using those as door stops, that's how bad those were lol.
There was some dude back in the 90's who advertised a whole bunch of factory test carbs for sale. He had a website in the 2000's. I bought what he said was the 1969 GS Stage 1 test carb off of him.
Gotta love these tid bits from behind the scenes from back in the day. A lot of the rigs we lust after are really a sum of parts that are in there own right are a sum of parts. And the more rare/elusive they are the more interesting it is. Cliff. That '265' that you mentioned, are there any applications with that number that would kind of match up to what you saw?
Yes, that’s the picture. Funny I don’t remember that conveyor or how the carbs were loaded onto it. That picture shows one aisle, and IIRC, there were many more just like it. One operator manned several stands, and a computer controlled pneumatic actuators that would turn the screws.
"Cliff. That '265' that you mentioned, are there any applications with that number that would kind of match up to what you saw?" The "265" I had in here would have been built by Rochester for a non Ram-Air Pontiac 400 engine for a Firebird with the manual transmission. The manual transmission carburetors with few exceptions where set up with slightly smaller main jets than their auto trans counterparts......
It is really kinda mind boggling to just much goes into making a car. Something I tend to over look. Just putting a assembly line together is amazing.
