There have been several threads on dual carb setup/tuning/problems. I've been working with multi carbs since the 60's, was into foreign cars back then and everything had them.
My comment is this; I think the most civilized and best option for an inline 6 is a triple 1 bbl setup. It is so much easier to maintain and easier to drive. I wonder why more people don't use them.
I haven't built one in years, but the way I built them was this;
On a Chevy, The middle carb was a standard w-1 of the size for a 235. If it was for high performance, the other 2 would be the same. If it was for street the other 2 would be smaller bore W-1's. The linkage was progressive. Up to 1/2 throttle the engine ran on the center only, just like stock. City, traffic, under 45, great mileage and predictable performance. Past 1/2 throttle and the end carbs opened in ratio so they were all full open at full throttle.
The end carbs would have the choke assemblies removed, the idle screws closed and the butterflies closed to just touching but not so tight as might stick.
Jetting was adjusted for the engine setup.
Couldn't be easier to maintain. You only set 1 carb for idle and there were no balance issues.
Since a 3 carb manifold is not much difference in price to a 2. The only difference in total cost would be the 3rd carb.
I'm interested in what others think.
The only reason the 2 ton doesn't have them was the look of the 2 oil filled air cleaners was more in keeping with the client's vision of the truck.
Jim, I totally agree! Whether a 6 or a V8, triple carbs is the way to better distribution and operation, as long as they're sized right. And they look even better!
the biggest reason I can see not to use 3 carbs on these trucks is the rear one runs into the fire wall. At least that is the conclusion I came up with. I never actually bolted the intake on, because it seemed really obvious it wasn't going to clear, but then again that was 20 years ago, and I may not be remembering correctly. This is the same problem I am having with my fuel injection unit, the rear tube runs into the firewall.
As mentioned by brokenhead, one hindrance to the use of triples seems to be some enthusiasts have encountered clearance problems with the rear carb.
We have done a number of triples for both Chevrolet and other USA sixes, always with good results. However, I don't remember any of these going into trucks.
As to linkage: Jim, you mentioned that you worked on a number of imports with multiple carbs. How many Jaguars or Healy 3000's with triples have you worked on that used progressive linkage?
Jon.
Good carburetion is fuelish hot air The most expensive carburetor is the wrong one you attempt to modify. If you truly believe "one size fits all," try walking a mile in your spouse's shoes! The Carburetor Shop
I think the style of linkage would depend on the carb size. Three small units should work together as one large equally spaced single carb. If the carbs are big enough to run just on the center one alone, then progressive linkage would be a better option. The engine would have better air flow at high rpm to accept the added end carbs input.
From what I have found on my engine (250 ci) the multi-carb setups do run slightly better. All around smoother running, but fuel mileage is about the same, starting about the same, and performance about the same, as my OEM carb.
I run them for the challenge of getting them right and perfectly tuned. For those not really into tuning and testing, single carbs are the way to go.
Try synchronizing, tuning, and rebuilding 4 diaphragm-venturi carbs on a Honda motorcycle for a while, and you'll have a bellyfull of "challenge". One nice thing about beating one's head against a wall is the fact that it feels so good when you stop doing it. One microscopic piece of dirt in one passageway of a single-carb setup can cause untold headaches. Why multiply the possibility of that kind of grief by a factor of two, three, or four (or maybe even 5 or 6)? Making things unnecessarily difficult for the sheer joy of self-inflicted pain has a name- - - - -it's called masochism! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Jerry - some truly enjoy working on these old vehicles. I still do, but less so than 50 years ago when I had less to do and did it quicker
And the factor of enjoyment alone is going to mean there is no "best for everyone" answer.
My experience over 50 + years of working on triples of solid vs progressive linkage on a 6 cylinder summerized:
Solid linkage:
(1) More homework (determining best carbs to use for the engine) (2) More expensive (3 carbs instead of two) (3) More difficult to tune for the novice (4) Somewhat better driveability (5) Smoother operation overall (6) More uniform power curve (more power at lower RPM's) (7) Somewhat better fuel economy
But for those who like progressive, go for it!
And Jerry, have never done the diaphragm carbs on a Honda, but we did install 4 Mikuni motorcycle carbs with the slides (like the S.U.) on a Pinto 2 liter and used solid linkage; won our class that year (and the sanctioning body promptly banned multiple carbs ).
Jon.
Good carburetion is fuelish hot air The most expensive carburetor is the wrong one you attempt to modify. If you truly believe "one size fits all," try walking a mile in your spouse's shoes! The Carburetor Shop
Jerry, do those Honda carbs have a vacuum port? If so use a tuning manifold made from four flexible tubing U-tube manometers mounted on a backboard. Takes all the work out of balancing four carbs.
They use a 4-tube water manometer to synchronize a TINY amount of vacuum bled off the venturi. Kawasaki, Suzuki, and several other 1-barrel per cylinder bikes use a similar system. I think the designers of those carbs have a secret agreement with Jim Beam, Jack Daniel, and Jose' Cuervo to boost sales of their products. You obviously haven't tried to make a living synchronizing multiple carbs. Everything works well on paper. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Jerry, I used the manometer set up on my Honda Four. I even mounted an aluminum manifold with four needle valves on the bike to make it easy to connect. You sure can say some stupid things!
the biggest reason I can see not to use 3 carbs on these trucks is the rear one runs into the fire wall. At least that is the conclusion I came up with. I never actually bolted the intake on, because it seemed really obvious it wasn't going to clear, but then again that was 20 years ago, and I may not be remembering correctly. This is the same problem I am having with my fuel injection unit, the rear tube runs into the firewall.
I think that might be the most valid reason that they aren't used on trucks. I should have remembered because I originally considered an early corvette setup (side draft) but it wouldn't clear the steering column.
But it did bring back memories of those great SU carbs I used to work on. Might be the best 1bbl carb ever built.
