I have heard of just running the center carb on a tri-power setup. I was wondering about just running the front or rear carb on a dual 4 barrel setup. I have a intake and like the dual carb look, but don't want the hassle. If I faked one by taking the butterflys out, blocking the fuel line, and using a thin plate under the fake carb to block it off, would the engine still run ok?
I guess I don't understand non functional shit on cars, especially hot rods. I remember being like 9 at an auto show and wondering why half of the cars there had side pipes that were blocked off and not attached to the exhaust system. It seems like that you wouldn't have a whole lot more time into getting both carbs working vs what you are proposing and it would not only look cool but be functional.
I have a question, if the linkage is hooked up and you have breathers on the carbs and the fuell stoped to all but one, how in the hell can you tell he is faking it??
OK tell me how I can make my bone stock 350 run good with two small holley's. There only 550 cfm. That makes 1100 cfm and if that's not more than a stock smallblock can handle I'll kiss my own ass!
You're gonna be dumping fuel like crazy into half the engine. There's a reason a single 4 barrel would be in the middle of the intake instead of way toward one end or another. It'll run like shit. There are 300cfm four barrel carbs out there, or at least, you can jet a four barrel to run 300cfm, so you need two smaller carbs and make them both run. Or, get yourself a pair of adapters and run two of those big Motorcraft two barrel carbs on your dual quad intake. They take the same big air cleaners and are the size of four barrels but they only have two holes. Just a thought.
Now don't get me wrong, and I could be full of crap, but I had a small block chev years ago and it had two AFB,s. It had progressive linkage, I can't remember which carb it ran off of, maybe it was the front one, but it ran fine on just the primaries of that one carb. Then when you nailed it the secondaries on the front carb came in and the rear carb came in. I'm pretty sure I'm right on this. I know it sounds goofy, but, I remember seting the idle on one carb only. You would think it would be on the primaries idleing on both carbs, but I think the back carbs primaries were shut clear down at idle. I think a street hemi was the same way. I believe when it got into the secondaries on the front carb, it started pulling the back carb open.
It is much more difficult 2 sync two carbs than it is to run 3x2 progressive set up. I don't think you will be able to run two carbs at either extreme end of an intake progressive. Based on my experience with evil Brittish cars, setting up a synchronized 2x2 system is hell. Anyone that has ever owned a running Brittish car has either become a carb deity or put a single weber on it. If it's a cash thing, just run a single in the middle til you save a bit. I ran my 350 like that for about 6 months with no problem. You won't set any records, but it'll go down the road just fine.
It seemed to work pretty well on the Corvettes of the 50s. as well as the 409s. Carbs don't just dump fuel into an air chamber.
This summer at my shop a customer brought in his Camaro and wanted me to set up his fairly stock 350 with a pair of 600 cfm Edelbrock 4 barrels. He insisted on having this set-up even though I kept telling him it was going to be way too much carb.(s). No matter what I tried to do with it it never ran right. It seems to me that with a tri-power manifold the center carb alone should work ok because it is pretty much centered over where a single carb would mount and therefore able to distribute the fuel close to properly on its own- even with the other two carbs in a tri-power set up disconnected. Whereas with a dual four barrel manifold one is in the front and one in the back. The one I set up had the linkage set to operate both carbs simultaneously. Like the others have said- with just one of the pair hooked up it you would really only be feeding four of the eight cylinders and it for sure isn't going to run like you'd want. Just thoughts based on my experiences... Jay
Seems to me a simple solution to running 2- 4 barrels without flooding a small engine would be to run both carbs but block off the secondaries. Then they wouldn't be FAKE........eh? the Dickster
I ran 3x2's in my '58 Impala SBC and used a 1/8" thick alumimun plate that I contoured cut to match the base of the carbs. I then placed it between the manifold and front. I did the same with the rear carb along with gaskets. I used a fuel block to feed each carb but I soldered plug the front and rear outlet so no fuel actually feed them. I fabricated a progressive linkage that appeared to be functional to all three carbs but it didn't engage the front or rear carbs. It was a sweet set-up and will do the same on the 348 engine that replaces the SBC in the Impala soon.
if it doesnt function, dont use it. fluff and fake is for porno, not hot rods & customs. -scott noteboom
I'd recommend this, since your engine is inexpesive to build up. Rather than fake out a carb for looks build up your engine and run duals. Talk to some people who build engines, see what they'd suggest search around here. I think gutting a carb is a waste of $ and counterproductive as well as cheesey. You'd be much happier as well with a little extra juice when you stepped on the accelerator. Just save some money and do it once.
If it was easy everyone would have multi carbs!!!! Use smaller AFB's they have a dry flow rating so with fuel they flow less. OR,,,,,Holley makes 390 CFM for this combination Bury you head in tech and LEARN how to tune them. Get rid of the "bone stock" cam if it is still in there. DONT fake it with a 2 X 4 if you do you will run lean on the rear of the engine and will destroy your valves and seats, maybe eat a piston too. My $.02 Dave
Dig up a pair of 400 cfm AFBs. Also, I noticed that someone mentioned "jetting down" carbs for less cfm; The cfm rating relates to airflow, which different size jets are not going to affect.
My friend built same kind of 3x2 set-up on his '31 Chevy about 10 years ago. Ever since I've been wondering what is achieved benefit here? -Don't need to tune it? But hey, you need to tune center carb anyway and also build those plates and fuel-line plugs. In fact, it might be more work. -Fuel economy? Hey, do these guys really drive more than a taxi-cab? And you also miss all the fun of 3x2... -Know-how? There's books, manuals, internet, other hotrodders... Go and find how it happens, it's easier than you thought. And it's interesting also! Listen to Chromedaddyo, he has good thoughts! And yeah; my opinion to original question; If you don't use both 4-barrels, other end of engine will starve and other end will get way too much fuel. Therefore you can't ever get it idle like it should. Also, it will destroy your pistons as chromedaddyo told. But you decide...
That's what I was wondering. The intake runners for the rear would basically be longer and I was wondering if it would lean out the cylinders. I was not looking for all of the opinions that everyone posted. I built pulling tractors for many years and had a lot of rules, I'm building this car the way I want to and don't care what anyone thinks about it. Building the engine for the extra CFM's would be no problem, but I plan to make this a daily driver without spending every dime I earn to finance it. I wasn't worried about raw fuel as it is atomized in the carb. I may mill the top plate, build a bolt on plate for three two's and just run the center carb. Ever seen a three-two tunnel ram? Thanks
I was not looking for all of the opinions that everyone posted. Get em now or get em later you are going to get them, opinions that is, not respect and admiration for the skill and time it takes to make what you think looks cool work. my two cents which you dont want to hear are if you want the cool then do it right. cory
3-2's on a sbc should be a blast, and you get your WOW factor, but I would still use all the carbs. A good progessive linkage system should serve you well, and if you can keep your foot out of it, it can be a practical driver. Good luck with it whatever you decide. BTW. In an effort to save on cash (1987) I drove a 2x4 tunnel rammed 351 600 miles with linkage to front carb only, let the other flow as idle. Burnt 2 valves in rear of engine in the process, one was sucked into the pocket! I am wiser now! Dave
A carb is designed to give the correct air/fuel ratio before the mixture passes over the butterflys and enters the intake manifold. It is all calculated on air velocity and the vacuum sensed in the engine. Any air after the initial start up has to pass through the carb. The carb senses the air flow and adds the correct amount of fuel for the air velocity and vacuum that it senses. If you over carb an engine you are not dumping too much fuel. What actually happens is that the smaller CI engine doesn't pull enough air through the larger carb and the vacuum is too low to atomize the fuel properly. The velocity is too slow to mix the fuel correctly in the carb. This factory Corvette runs around town on the back carb only. Actually it runs on the 2 primary butterflys of the rear carb. The front cylinders still get the proper air/fuel ratio just like the rear cyls. There was no epidemic of burnt valves or fried pistons from a too lean condition caused by the carb location. This is a little 283! The carbs were sized for the needs of the engine. It works! When you nail it the the secondaries open on the rear and the front carb opens allowing more air in that mixes with the fuel in the front carb before it enters the intake just like the rear carb. The air/fuel mixture is determined inside the carb/s before it gets to the intake. Unless there is an vacuum leak there is no way for the mixture to "lean out" inside the manifold. 6-2 were made for racing. Wide open throttle. They were never intended for street driving. To use them on the street successfully, compromizes will have to be made. IMHO Progressive linkage or blocking some off is the usual way of dealing with a race car induction system used on the street. You do want to drive it don't you? BTW the plates under the carbs only need to withstand 14.7 pounds per sq. in. pressure...(atmospheric pressue at sea level) unless it has a blower of some kind.
I wasn't trying to be an ass, I just plan to build this one the way I want to build it with nobody to please but myself. No matter how I do it, it will be right for me.
what are you talking about?!! fake is plenty trad..look at how much fake stuff they had back in the day..dummy spots, dummy lakes...depending on if it was a completely show car,plenty of the stuff was fake!the dummy lakes on the golden penny werent even connected to the car,they just dragged on the ground!also,why would you have to take out the butterfies?if you block off the bottom of the carb and the fuel lines,sounds like enough to make it a dummy to me.no need to gut an otherwise working carb when you might want to make it functionable later.i just dont understand not running all 3 on a 3x2 if you pay all that $$ for the intake...unless it's too much for your engine which i higly doubt creepy
You mean them guys really aren't hung like donkeys and can go blow like old faithful on demand. Damn I'm so disappointed. You have a lot of variables going on here. Does your intake share a common plenum? Do you have vac secondaries? Can you get your hands on smaller carbs? ect. I'm going to say that you should probably build it right to start with. I know that's not what you want to hear but that doesn't change the fact that if you want to run 2 fours you should set it up to run 2 fours. Remember a wolf in sheeps clothing is far more effective in the real world than a sheep in wolf's clothing.
If any of you guys with blocked off carbs dont want em just send em my way I think I could use em. Especially if they are 97's or 94's. Just a thought. LOL Sam
Hey casepower, Running one full 4barrel on a 2x4 manifold would have real bad fuel distribution. Runnin' just on the primary of the rear carb only would be you best chance with your setup but, it would be under carbed. Usin' the primary of the rear carb (for idle and part throttle)and the secondary of the front carb(3/4 to full throttle) would be almost like a single 4 bbl. With that you still need progressive linkage. It's like Tommy said. Idle and part thottle runs on the primary of the rear carb. The Edelbrock 2x4 set up works real good on mild small blocks. Check out their linkage and tech stuff to help you with your project. To much fuel pressure is the biggest problem that I've seen with multicarb setups. Mostly with Rochesters and Edelbrocks. Holley can take more pressure. I know that is not really what you're askin' and it is more cfm than you need but,the two small 4 bbls do work OK when progressive. Have fun,Smokey Do you have the carbs yet?
The car in my avitar is a stock 350 with 2 AFB's and runs fine. It idles off both carbs. (Never took the time to block off the front carb idle circut) It starts easy with no choke idles perfect even cold. I have had about 10 cars with 2X4 setups on them and they all ran fine with little maint. Idealy it should run at idle on the front 2 barrels of the rear carb and the linkage should slowly bring in the other 6. If you use old AFB's and don't over jet them they have always worked great for me. Sure a single 4 barrel would probably run a little better, but whats the fun in that! Get them both working, it won't be any harder than trying to fake it. I'm putting 2 dueces on my Buick and 6 Dueces on my 34 truck and I will make them all work if it kills me.
Run the 500cfm carbs like suggested by all manufactures, and yes it will still be very streetable, wont waste gas, WORK, and remember its HOT ROD not FAKE ROD!!
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