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  #1  
Old August 4th, 2008, 06:17 PM
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Default Ultimate carburetor

Alright, so bear with me here, I have a question. I've been doing a bit of research on different carburetors and what not, but I haven't quite found what I'm looking for. So lets just say you could choose any carburetor(s) you wanted to put on say about a 230 cubic inch engine. Low RPM, looking for tons of low end torque, maybe good economy (not worried about MPG for cost reasons, I'm looking to have a very large mileage range between fill ups to increase the time I can travel without worrying about finding a gas station) What would be the best type? Small 4 barrel? 2 barrel? Dual singles? Don't worry about if there is an intake manifold that has the right bold pattern, thats not important. What would be the ultimate carb setup? Wild and crazy, realistic, lets hear your ideas.
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Old August 4th, 2008, 06:39 PM
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The ultimate carburetor is fuel injection.......

No trying to be smart about it, but in reality, a carburetor is nothing more than a crude mixing device, subject to so many outside influences, that it is hard to get a one-size-fits-all carburetor.

Intake tract design is a huge factor first of all. The length, and size of the runners has a very big effect on mixture and velocity of what enters the engine.

Intake air temperature (ideally 140-160 degrees F) is very hard to maintain in an older thermostatic air cleaner system to promote the best combustion possible. Also keeping the intake temperature consistent is a must. That was done crudely for many years with heat risers and coolant circulation. Even EFE electrically heated grids were used too, but they proved to burn out in time.

Several smaller venturis are better than one large one, because the air flow is more evenly introduced and more efficiently atomizes the fuel to mix with incoming air. Ideally a 14.7 to 1 ratio of air-to-fuel is sought after, but next to impossible to maintain with a carburetor.

Carburetors are also subject to one factor that cannot be controlled: wear. Throttle shaft wear, and other moving parts make maintaining that 14.7 to 1 even harder. Couple that with engines of poor design to start with (i.e. large intake valves, huge camshaft durations and overlap) and they don't respond well no matter the good intentions to make them better.

Consider this as well: The last car to use a carburetor in production was a 1989 Hyundai Excel. The last truck was a 1993 Isuzu pickup.

Let's just say they have their limits. Efficiency is not one thing they were ever known for.
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Old August 4th, 2008, 08:06 PM
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I totally agree with Randy, Use a 4.3 throttle body F.I. but a very good simple carb is the 2brl rochester off of say a 75 v6 buick, my 68 chev had one also. I installed a holly 4 brl and header w 2.5" exh on a 300 ford and boy did it wake up! I used to put a roch. 2 brl on it to pass emisions and it too worked well. With the holley and the overdrive trans it got (1/2 ton 84 f-150) 21mpg a couple times going real easy staying out of the last two venturies. The 2brl came off of that 3.8 75 buick.
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Old August 4th, 2008, 08:15 PM
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For optimum cost vs performance/efficiency use a weber carb for a 258 motor. Better efficiency, 2 bbl and great offroad performance.
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Old August 4th, 2008, 10:18 PM
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I forgot about that one, they have a lot of jetting differences, they came on v6 capris, and I'm sure many others. And the mounting flange might be closer to the civy 230 2brl
flange. Brandon, you have one of those don't you? A header and a proper supply of petrol and you've got one of those hot Argentine motors. COOL!
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Old August 4th, 2008, 10:29 PM
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The Argentine motors didnt get hot until they made a new intake where the intake had 1 port per cylinder with MUCH more flow than the stock manifolds our trucks have/had...
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Old August 4th, 2008, 10:35 PM
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Side draft Webbers!!!!!
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Old August 4th, 2008, 10:42 PM
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In response to the original question....

The stock 1920 1 barrel has worse fuel mileage and less power than the approx 350 cfm Holley 2415 2 barrel I now have from a civvy 230...there was also a 2300 Holley 2 barrel used on civvy applications, also approx 350 cfm.

The 2 barrel has noticible power and mileage increases as one doesnt have to hold the throttle open as far or as long to get the same speed.

With a stock 230, roughly 9 MPG was the limit. With a civvy ignition, Selectros and the 2 barrel, these changes done in stages not all at once, netted 12.25 MPG highway and single tanks in excess of 280 miles without a stop.

NOTE: The change to the 2 barrel DOES lower the torque right off the line. One can still start the truck n gear with the starter button and idle along at 500 rpm in 1st gear but when taking off from a dead stop 2nd gear, high range, one will notice the engine lugging a little where it didnt with the 1 barrel.

So, for low end torque, as small a venturi or venturis as possible...if there is even a 300 cfm or smaller 2 barrel out there that would fit...

If you are willing to sacrifice a little on the low end you can get better mileage and power across the rest of the rpm range with approx a 350 cfm carb.

Find a way for the intake side of the head to breathe better and you can go higher...as it is stock, the ports from the intake into the head, when figured in area, are only a slight fractional size different than the throttle plates on the 350 cfm 2 barrel...I believe the difference was less than 1% in total area across both...real close.
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Old August 5th, 2008, 07:13 AM
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I forgot to add, with the 230, the head design will pretty much limit anything you do. The port design is pretty rigid and not able to be modified for better flow.
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Old August 5th, 2008, 07:35 AM
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X2 or x3 or whatever it is for weber.

I dislike electronics and will gladly sacrafic a smidge of economy in favor of less headaches.
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