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| biiiiiigggggg carbs https://slantsix.org/forum/viewtopic.php?t=26427 |
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| Author: | dusterdude225 [ Fri Dec 28, 2007 4:45 pm ] |
| Post subject: | biiiiiigggggg carbs |
im looking at buying a 600 cfm rockchester quadrijet with those rear venturi the size of my fist for my slant 6 and i also want one of those big cams from clifford performance will the carbwork good with that cam |
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| Author: | Greg Ondayko [ Fri Dec 28, 2007 5:09 pm ] |
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You's have to give specifics on the Cam Compression Valve size etc. The 600 is probably a bit on the large size - You're engine Will probably like a 350-500 CFM even better. Greg |
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| Author: | Doctor Dodge [ Fri Dec 28, 2007 7:49 pm ] |
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A small engine like a SL6 will run better with a smaller cam and a smaller carb. DD |
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| Author: | Rug_Trucker [ Fri Dec 28, 2007 9:03 pm ] |
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I thought those Qjets were 750cfm? They must come in different sizes as I would bet the 454, 455, and Cadillac ones might be bigger? When I get a 4bbl intake I want to try an 800 Thermoquad. I have some metering rods that are really lean. I have the small jets etc. In theory a Qjet, AVS, or Thermoquad will adjust their size by engine demand. I see an AFR meter in my future. I have a '87 Mopar Qjet on my 360 van. |
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| Author: | slantzilla [ Sat Dec 29, 2007 6:18 am ] |
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V-6 Buicks used a Q-Jet that was rated at 600 CFM. However, the secondary doors were pinned so they would only open halfway. V-8 Q-Jets were rated at 735 and 800 CFM. A smaller carb will be easier to tune and more responsive though. |
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| Author: | FrankRaso [ Sat Dec 29, 2007 6:43 pm ] |
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I believe that the Quadrajet came in a 750 CFM and 800 CFM sizes. The difference between the two is in the size of the primary venturis. The 750 CFM carb has 1-3/32" primary venturis while the ones on the 800 CFM are 1-7/32". I replaced the 625 CFM AFB that I had on my car previously with a 750 CFM Quadrajet and I like the driveability of the Quadrajet much better. I've been too busy lately to drive my car very much so it still has the OEM setup (never been opened) of 1977. Maybe this summer will get around to jetting it properly. It doesn't matter what cam your car is equipped with because the QJ only flows as much air as the engine requires. The air-valve secondaries will never open fully on a slant six and likely never did completely when it was on the 350. I have the DC P4120243 cam, 318 valves, stock automatic transmission, and 2.93:1 axle in my car and I can hear the secondaries cracking open occasionally at around 60 mph. My feeling is that most people don't like the Quadrajet because it is more sophisticated than Hollies or AFBs and therefore a bit more involved to set up. I believe most people who give up on the QJ do so because they don't want to take the time to learn how to tune it properly. My 2¢. |
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| Author: | argentina-slantsixer [ Sun Dec 30, 2007 4:49 am ] |
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I know that most people don't like them (I think that's because they're not familiar with them) but there's a wide variety of small 4 barrels that are indeed very suitable for the slant six in almost any form from dead bone stock to mildly prepped, I'm referring to solex pierburg 4 barrels (like a rochester but smaller, they came in BMW's from the 80') and Ed (emsvitil) pointed out another great option and that's the Zenith-Stromberg 4 barrels that came with some jap cars like mazdas |
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| Author: | slantzilla [ Sun Dec 30, 2007 5:51 am ] |
| Post subject: | |
The Q-Jet is actually a very simple carb both in terms of pieces in it and ease of tuning. Some models had issues with the fuel leaking out of the float bowls, but fixes for that have been available for years. The biggest drawback was that small fuel capacity of the float bowl, but that should never even be an issue on a Slant. I would rather tune 10 Q-J's than one Thermoquad any day of the week. 
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| Author: | sandy in BC [ Sun Dec 30, 2007 8:27 am ] |
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The things I like about Q jets: They are a dime a dozen...I must have at least 6-7 They are super flexible....I went from a small valve 9:1 CR 350 with a dual plane manifold to a big valve 400 10.5:1cr with a Victor manifold and did not have to touch the carb..... They are stealthy....everyone thinks you are slow when they see a Qjet. |
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