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| 2 bbl vs 4 bbl https://slantsix.org/forum/viewtopic.php?t=34115 |
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| Author: | jmtrops [ Thu Mar 05, 2009 6:59 am ] |
| Post subject: | 2 bbl vs 4 bbl |
If they are the same cfm what are the advatages and disadvantages to having a 4 bbl vs a 2 bbl carb? |
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| Author: | SlantSixDan [ Thu Mar 05, 2009 7:39 am ] |
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Need a more specific question to give a useful answer. What kind of vehicle are we talking about (specifically)? How, where, when, and how often will it be used (specifically)? How is its engine built and configured (specifically)? Or is this purely a theoretical thought exercise? |
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| Author: | wvenable [ Thu Mar 05, 2009 7:51 am ] |
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The four bbl is progressive. This means it runs on its primaries until you kick it. If you keep you foot out of it your mileage will most likely increase because the primaries are smaller. Most 2bbls are synchronous both venturis work at the same time. There are some progressive 2bbls, Weber would be one example. These run on one bbl until you put your foot down then the other bbl joins in. The most important would probably be matching the size (cfm) carb for your application. Go to the article section of this site (lots of good stuff there) and check out the carb article by Josh Skinner. Hope this helps to answer your question. |
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| Author: | CARS [ Thu Mar 05, 2009 8:57 am ] |
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X2 on Josh's article. |
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| Author: | sandy in BC [ Thu Mar 05, 2009 9:41 am ] |
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Moving from a 1 barrel carb to a 2 barrel carb is a good move with measurable results. Moving to a 4 barrel requires considerable engine work to see measurable results. Think cam , compression and convertor/gears for starts. Its no harder to run 16 seconds with a 2 barrel than a 4 barrel. I would not install a 4 barrel unless I was convinced a 2 barrel did not have enough for my build. ....and then Id EFI instead. |
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| Author: | jmtrops [ Fri Mar 06, 2009 5:14 am ] |
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I have a 2bbl intake so I am leaning on going with a holley 2 bbl. Compression will be 8.6-8.8 range, head has over sized valves and ported, cam will be comp cam 264 or erson 270, I will have a better than stock torque converter and some day I will have 3:55-3:91 gears. Will the holley 350 be big enough or should I get the 500? Is this too much for the 2 bbl? |
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| Author: | Dart270 [ Fri Mar 06, 2009 5:20 am ] |
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With that motor buildup, the 350 should work very well. Seymour has been in the low/mid 14s in his street car with a Holley 350. 500 works great too, and I've had luck running that on a wide range of Slant 6 buidups. I would stick with the 350 with that engine buildup. You really won't need more unless you go to higher comp or a substantially bigger cam. Lou |
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