Technical 3 x 2 virgin, break me in easy

I recently acquired a 3x2 setup (sbc w/rochesters) the end carbs have mixture screws which means they have idle circuits, but the witness marks of carbon build up under the air cleaner lid show that all three carbs worked.

So what is the big deal of having or not having the idle circuits in the carbs ?

I've seen the Speedway bases and also heard about a way to plug the factory bases but is there really a need ?

 

I have run 3 X 2 set ups, way back in the 60's and 70's with the end carbs having and not having the needle valves.
From my experience, it didn't make a difference at WOT or on idle. When on idle, if set correctly, you are only running on the middle carb, so the end carbs are not coming into playl. I'm sure there will be lots of other comments
but this is from my personal experience. Bob

 

Your carb linkage has all three opening at the same time. The plugged idle circuits are used with progressive linkage. Maybe you are ok. I still haven't got mine working good.

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I would prefer to have idle on all three because I would have the linkage one to one.

 

I’ve always idled on all 3 or on 2 if dual quads even if progressive. The only SBC I had which I didn’t had 348 carbs without the the mixture screws.
It many not mean much but you do use a small amount of gasoline idling and keep the needles and seat from sticking. Running also vibrate the carbs and can cause flooding; you need to “exorcise” once in a while.

 

I run that set up on the 57. It came with two primary carbs and one original end carb. After much advice from many old timers, I plugged the idle screws on one primary carb with JB weld, made up a progressive linkage for end carbs. This works great BUT alot of work to make sure end carburetors butterflies stay closed. This was key to making my car run correctly. Good luck!

 

You have 3 carbs you dont have a 3 deuces

 

I run 3x2 with no idle circuits on the end carbs. Works ok but I think I’d rather have a setup like yours. You can adjust them to cover up the throttle plates not being perfectly closed. On mine I spent a lot of time honing and polishing the plates to get them to seal at idle otherwise they are two big vacuum leaks. Linkage would be easier on your too. Problem with yours may be wide open from a stop may be too much carb. With progressive linkage you can bring the secondaries in when you want.
Good luck


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. That's the way they were refered to back in "the day" It's also the way I still refer to a 3x2 set up. Another term was trips. Meaning triple carbs

 

Looks like 3 Rochester 2GCs with the Cs (chokes) removed from the end carbs. Also note the notch on the top ring used for air cleaner alignment on a single 2 barrel carb setup; true tri-power 2Gs don’t have that notch, because the multiple-carbs align the air cleaner. I believe GM, or certainly Chevrolet, used the 3 2-barrel setups with the end carbs activated by vacuum. Many of us change that to a mechanical progressive setup either because we don’t have all the original parts, or we prefer the progressive method. In the progressive method the end carbs are akin to the secondaries on a 4-barrel carb. As such they play no role in light-throttle operation, have no choke or fast-idle mechanisms, nor idle mixture screws. You can make non-tri-power carbs work as end carbs if you follow the many tips in the web. Check The Carburetor Shop website for one.

I’m not sure why one would want to run the 3 Rochester 2 barrels as one carb rather than the vacuum or mechanical progressive setup. I think you will have too much CFM for low-speed operation and it will be a mess. That’s not the case with some of the other smaller multiple-carb arrangements (Strombergs, for example).

What we need is a bit of knowledge from @carbking here on the HAMB. I imagine he’s biting his tongue out of politeness.

School us good sir.

 

I do run all my (tunnel ram, blower, low profile and soon crossram) 2x4 setups with 1-1 linkage with absolutely no issues, the engine I plan on using this on has two Carter 600 cfm Competition Series carbs on it currently. I do spend plenty of time tuning them to get to the point of having no issues, I'm not scared of 1-1 linkage by any means.
Thinking about this I think leaving the idle circuits in would actually help keep the outside carbs cleaner with today's fuel, since they would constantly have fuel flowing through them instead of only at wide open throttle (or there abouts).
But even with having a progressive linkage wouldn't the outer carbs just idle until they were activated by the linkage when they would go from idle to wide open ?

 

Yes.

 

I had a 58 Impala with a 3 speed, 348 and 3X2 setup. I was only 17 when I put the 3X2 setup on it. I didn't understand how the vacuum setup worked. I helped a buddy put a 348 Tri Power in a 55 Chevy and it had a nice progressive linkage. I studied it and went home and made one. The only problem I ran into was that on occasion, the end carbs would not close all the way and it would barely idle. My fix was to quickly open the throttle all the way and side step the pedal. That usually worked. I think the real problem is my link between the end carbs was a bit too light and would flex. I think that old Impala was the most fun street car I've had. Cruise on the center carb and get a big kick in the butt when you opened the end ones. I've even nursed my way home after running out of gas by kicking in the end carbs, accelerating, then shutting off the engine and coasting. Repeat until the end carb are dry or you've reached your destination. Mine was a stock setup, so the end carbs had no idle circuits.

 

Now just remember, if you go with progressive linkage you’re going to have to take it out regularly and stick your foot in it enough to be sure that the end carbs get fresh gas in the bowls.


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Swade, the avatar brings class and beauty to the site. Truly an artistic statement.

 

Hello,

As others have said, those three carbs are set up to run with your progressive linkage. Your photo shows something is missing from the middle carb linkage. The last part of the progressive set up is gone. The loose rod end shows something is not right. Where is the final linkage to the firewall? The long solid rod seems like the two outside carb connecting rod.

It won’t work unless you have the final linkage correctly installed on your set up. Sure, the carbs will open up as it is set up, but you are missing a valuable part. For us, the dragstrip is a good place for full on acceleration runs with the progressive linkage. But, daily driving did not feel fun, as the linkage had its problems versus the stock vacuum set up.

Jnaki


When my brother purchased his new 58 Impala, he ran with the stock vacuum set up on the three carbs. It was the most reliable system for 4 years. Several A/Stock car class wins at Lion’s Dragstrip and consistent driving daily to school/job worked out well. He never tried the progressive linkage as he was out of racing and driving the Impala during his recovery.

When I was driving the Impala as part of the daily cruising scene, a friend and I raced. The vacuum hose dropped off about a few seconds after the full acceleration from the starting line. Usually, the secondary carbs kick in and an immediate car length advantage kicked in with the two outside carb extra power. But for some reason, that pesky 1956 301 Chevy stayed even with me by the 1/8 mile. For the last part, we stayed that way. I could feel that there was no extra power and could not figure out why.

Upon pulling off to the side of the road on a side street, out came the flashlight and the inspection started. The first thing was looking at the carbs. Then the black vacuum hose was sitting near the center carb near the hose connection, not on the connection. The instant I put the hose back on, the two outside carbs came on and I could hear the extra power.

I wrapped some tape on the connection and drove back to the drive-in parking lot. We needed to race again, with my Impala at full throttle power from all three carbs. When I told the 56 owner about the hose, he said he could not race again, as fast I got the information out. He knew with the two extra carbs actually working, he had no chance to win. I wanted to show him a car length tail light scenario to keep him honest.

It never happened…he said something broke on his 301 SBC and did not move from the lot. Everyone saw the look on his face when I told him of the loss of the two carbs in the close race. They all knew why the 56 owner did not want to race again.


For the next three years, I only used the vacuum set up as it was reliable for everyday drives to school and cruising. We tried a nice progressive linkage system we made and it worked like a charm. But, it was not for daily driving and was not liked by me or my friend who tried to drive the Impala around the block. The normal driving was hindered by the throttle stops and the outside carbs were not necessary for everyday driving. So, off of the 348, the progressive linkage system came and I gave it to another guy with a 3 carb set up on a 283 SBC motor. YRMV

 

The 3x2, 3 deuces, tripower, trips whatever one wishes to call them, can be made to work in a variety of ways, albeit never as well as a properly sized single carb or dual carbs on an 8 cylinder engine.

There is no "one answer fits all"; and the various responses in this thread prove that. Best to determine one's needs, set it up that way, and tune from there.

Idle on all three, as mentioned by Jimmysix, allows a small amount of fuel to be used by all carbs, which helps prevent the float/float valve circuit from sticking, and also keeps fresh fuel in the bowls.

There have been billions of pixels disturbed trying to convince others that either progressive or vacuum linkage is best.

Historically, linkage was vacuum, as tripower was sold on many luxury cars as an expensive option to those who were not really gearheads. The vacuum prevented the throttles on the end carbs from opening too early. Progressive linkage was available as an over the counter "racing" option. From memory, the first progressive linkage from the factory on new cars was the 1965 GTO.

Linkage for racing probably should be progressive. Linkage for the street can be either, but if progressive, the driver needs to know to restrain his/her foot until the engine RPM was ready for the extra CFM.

Professionally, I LOVE tripower! After all, I get to sell three rebuilding kits rather than one

But from a true performance standpoint on a V-8, the best bet is to remove the tripower, and replace it with either a single carb, or dual carbs, or four carbs..... Even Pontiac paid Carter to sabotage the Carter AFB so the less expensive single four engine would not outrun the more expensive tripower engine on the GTO!

Historically, tripower came into being as a cheap way to increase CFM (larger single carbs were available, but more expensive, the Ford EE-1's were dirt cheap in salvage yards everywhere). The larger carbs were NOT cheap.

So, enough rambling. Set it up the way YOU like it, and tune from there.

Jon.

 

Is there a need?
Not really, but proper end carbs set up correctly with sealed butterfly plate and progressive linkage make tuning soooo easy. The end carbs have just 2 jobs, seal off air when closed and when open dump the right amount of fuel. Usually the end carbs are Either closed or fully opened.

Running 3 carbs like yours is set up you’re going to need 3 balanced carbs, 3 idle circuits operating together in unison, 3 mid range again in unison and 3 WOT circuits operating in unison. At least 3x the time and trouble at minimum but certainly doable.

 

Speedway, order the tri power kit, put it together and drive

 

I never had a 3x2, but reading this thread opened my eyes to something...that is keeping fresh gas in the end carbs.

 

I'm going to have to change the name of this thread to 1 x 2 - 2 x FAKES !

That middle carb had to be one rich burning carb to leave witness marks at all 3 positions.

 

Man, that’s disappointing! I see you scored a tri power, Swade! Those missing parts should be easy to find. My Ford FE 3x2 came from the factory with progressive linkage and idle circuits in all three carbs. I can’t help you on tuning, as I have got mine running yet! Good luck.






Bones

 

Disappointed but not a deal breaker, I'll get those 2 carbs right and have a true three two setup on this engine.

 

As stated above, the end carbs are not in use until you put your foot down. That is why it is critical to seal butterflies closed while cruising.
This was, again, the hardest part of my setup.
Good luck and have fun!!

 

No expert by any means but I did set up my rochesters. I put new springs and levers on the out board carbs and left a little play in the rod. This allows both carbs to close fully. One won’t stop the other from closing. GM did the same thing by using a solid rod with 90 degree bends and one of the levers was slotted so it had play. Charlie Price has some great videos on YouTube on how to rebuild and set up.

 

A PCV on with tired rings would do that too.
That’s one way to seal up those end carbs

 

I know it’s been a year and a half but has anyone here successfully used a kit from speedway? Seems like the outside carbs are nothing but a vacuum leak. Trying to fit the blades better. Wondering if it’s easy to use the stock bases with plugged idle circuits.

 

Swade: Now that this thread has reappeared, I noticed your air cleaner setup. Could you post some pictures of it? Probably made of unobtanium but would be great if I could locate one.

 

Had tripower on my 65 Goat and never had any problems with it....Had to jet it up when changed cams....Very trouble free and performed well....

 

I can't speak to the speedway kit but I am very happy with the vintage speed kit. It ran pretty good right away. I still haven't done any tuning and expect it to improve. It's on a stock 62ish 283.

Phil