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2bbl vs. dual 1bbl revisited
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Author:  64'4$peed [ Wed Jul 05, 2006 3:18 pm ]
Post subject:  2bbl vs. dual 1bbl revisited
A friend of mine who runs dual 1bbl's (rochester's I think) on his chevy straight six told me that a 2bbl carb is going to give much better performance then the dual 1bbl setup. and that a dual setup would yield only a 4hp increase over the stock 1bbl setup. he said he only ran duals cause they look cool. no argument there but I think his performance theory is way out of whack.
Author:  RossKinder [ Wed Jul 05, 2006 4:15 pm ]
Post subject:  Re: 2bbl vs. dual 1bbl revisited
Quote:
A friend of mine who runs dual 1bbl's (rochester's I think) on his chevy straight six told me that a 2bbl carb is going to give much better performance then the dual 1bbl setup. and that a dual setup would yield only a 4hp increase over the stock 1bbl setup. he said he only ran duals cause they look cool. no argument there but I think his performance theory is way out of whack.
I've heard rumors that dual carbs need synchronizing :!: :shock: :lol:

(Sorry. That was supposed to be a humorous way of suggesting your friend hasn't done that well syncing his.) :oops:
Author:  NewLancerMan [ Wed Jul 05, 2006 4:51 pm ]
Post subject: 
That is silly, but Ross is right poorly synced carbs will cause all kinds of problems

mine is definitely more powerful. Not 4 HP, which honestly is not even measurable seat of the pants
Author:  64'4$peed [ Wed Jul 05, 2006 5:01 pm ]
Post subject: 
his carbs are sync'ed right. His 49' chevy custom runs like a top. I find his information to usually be very helpful and right on the money but this one I couldn't buy. I'm guessing if anything dual 1bbl would have more power then a 2bbl right? I just couldn't see the logic in what he said.
Author:  RossKinder [ Wed Jul 05, 2006 5:18 pm ]
Post subject: 
Quote:
his carbs are sync'ed right. His 49' chevy custom runs like a top. I find his information to usually be very helpful and right on the money but this one I couldn't buy. I'm guessing if anything dual 1bbl would have more power then a 2bbl right? I just couldn't see the logic in what he said.
That would depend in part on the air flow of the different carbs. Based primarily on throat sizes, if your dual singles breath more cubes of air (which, of course, brings in the fuel) than what the 2bbl does then you have a point.
Author:  SlantSixDan [ Wed Jul 05, 2006 5:45 pm ]
Post subject: 
Quote:
That would depend in part on the air flow of the different carbs. Based primarily on throat sizes, if your dual singles breath more cubes of air (which, of course, brings in the fuel) than what the 2bbl does then you have a point.
Hey, lookit there, it's raining sudden carburetor experts in Ooltewah! :lol: :lol:
Author:  CStryker [ Wed Jul 05, 2006 5:51 pm ]
Post subject: 
Quote:
Quote:
That would depend in part on the air flow of the different carbs. Based primarily on throat sizes, if your dual singles breath more cubes of air (which, of course, brings in the fuel) than what the 2bbl does then you have a point.
Hey, lookit there, it's raining sudden carburetor experts in Ooltewah! :lol: :lol:
Well, it /is/ a little bit of an oversimplification, but by and large, his point does seem valid Dan.
Author:  tophat [ Wed Jul 05, 2006 5:57 pm ]
Post subject: 
I would think that duals would have better fuel distribution.
Author:  Slant n' Rant [ Wed Jul 05, 2006 6:20 pm ]
Post subject: 
Would I be correct in thinking that a chevy stovebolt would have more limitations to bolt on HP? A slant should be able to take better advantage of a dual setup due to superior intake configuation compared to the chevy?(no ram effect)They are both 6 inlines but are not 'birds of a feather'.There, do I get my diploma in carburation? :P
Author:  SlantSixDan [ Wed Jul 05, 2006 6:49 pm ]
Post subject: 
Quote:
Quote:
Quote:
That would depend in part on the air flow of the different carbs. Based primarily on throat sizes, if your dual singles breath more cubes of air (which, of course, brings in the fuel) than what the 2bbl does then you have a point.
Hey, lookit there, it's raining sudden carburetor experts in Ooltewah! :lol: :lol:
Well, it /is/ a little bit of an oversimplification, but by and large, his point does seem valid Dan.
Oh, in general it's perfectly valid. I was just razzin', is all.
Author:  RossKinder [ Wed Jul 05, 2006 9:11 pm ]
Post subject: 
Quote:
Oh, in general it's perfectly valid. I was just razzin', is all.
Well, now, I'm glad everybody understands that clearly.
Author:  emsvitil [ Wed Jul 05, 2006 9:22 pm ]
Post subject: 
2 1bbl carbs are usually on 2 manifolds....

So 1 2bbl carb is better.


With 1 2bbl carb, each cylinder can pull from BOTH barrels of the carb.

With 2 1bbl carb, each cylinder is pulling from 1 barrell only.


So unless each 1bbl carb has the air flow capacity of the 2 bbl carb, you're better off with the 2bbl carb........
Author:  CStryker [ Wed Jul 05, 2006 9:41 pm ]
Post subject: 
Quote:
2 1bbl carbs are usually on 2 manifolds....

So 1 2bbl carb is better.


With 1 2bbl carb, each cylinder can pull from BOTH barrels of the carb.

With 2 1bbl carb, each cylinder is pulling from 1 barrell only.


So unless each 1bbl carb has the air flow capacity of the 2 bbl carb, you're better off with the 2bbl carb........
Huh? With dual 1bbl carbs, each carb is only looking at three cylinders instead of six. I don't understand how (in theory) two one barrel carbs wouldn't perform equally to one two barrel carb of twice the size...
Author:  emsvitil [ Thu Jul 06, 2006 1:22 am ]
Post subject: 
Quote:
Quote:
2 1bbl carbs are usually on 2 manifolds....

So 1 2bbl carb is better.


With 1 2bbl carb, each cylinder can pull from BOTH barrels of the carb.

With 2 1bbl carb, each cylinder is pulling from 1 barrell only.


So unless each 1bbl carb has the air flow capacity of the 2 bbl carb, you're better off with the 2bbl carb........
Huh? With dual 1bbl carbs, each carb is only looking at three cylinders instead of six. I don't understand how (in theory) two one barrel carbs wouldn't perform equally to one two barrel carb of twice the size...

Say the 1bbl carb is rated 100cfm, the 2bbl is rated at 200cfm.....

With the split manifold, one of the cylinders needs air every 240degrees of engine rotation (out of the 720degrees need for complete 4-stroke cycle). So each cylinder pulls on that 100cfm carb all by itself, and the max flow to that cylinder is limited to the 100cfm

With the single manifold, one of the cylinders needs air every 120deg of engine rotation. And although there's overlap of cylinders needing air, the 1 cylinder does at some point have most of the flow capacity of 2 barrels available to it during the intake cycle (or slightly less than 200cfm).
Author:  RossKinder [ Thu Jul 06, 2006 9:02 am ]
Post subject: 
Quote:
Well, it /is/ a little bit of an oversimplification, but by and large, his point does seem valid Dan.
Precisely. As a teacher I found that in early reponses "oversimplify" is occasionally more useful than "lock & load." :wink: And, of course, I did say it was only part of it.

Thanks
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