Chevy Dualjet carbs?

CZLN6

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Howdy:

I'm looking for info on the rochester Dual jet carb, intake and exhaust system that came on Mid-80's Chevy pick-ups. What years were they produced? Any websites or links?

Thanks, in advance.

Adios, David
 

CZLN6

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Howdy Back SR:

Yes, I found that one, but it doesn't give the specific info I'm looking for. So far, I've found that the progressive Rochester two barrel and the dual exhaust manifold was a one year option in 1983. According to Tom Langdon the whole system upgrade was good for a 20 - 25% increase in power and possibly an increase in mileage for a factory designed bolt-on. The two most promising listing #s are 2SE and/or E2SE.

Questions-
*Is it a true dual stage carb? It is sometimes describes as the right half of a Quadrajet, and other times as the front half.
*What is it's rated CFM?

Thanks Strange. Keep it coming.

Adios, David
 

jamyers

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CZLN6":a3hjoxn0 said:
Questions-
*Is it a true dual stage carb? It is sometimes describes as the right half of a Quadrajet, and other times as the front half.
*What is it's rated CFM?
Dualjets are the front half (primaries) of a Quadrajet. The non-electronic ones make good 2-bbl carbs - great venturis, boosters, and lots of tunability between the rods/jets/air bleeds.
I'd get a copy of Cliff Ruggles book on Q-jets, most of the work to be done on a Q-jet is on the primary side and float bowl.
I'm not familiar with any Rochester progressive 2-bbl carb, got a link to info on one?

Regarding the CFM ratings, I don't know directly, but on a Q-jet the primary side was either 150 or 200 CFM, depending on whether it was a 750 or 800 CFM Q-jet (all Q-jet secondaries are 600 cfm). Look down inside the primary bores to see the difference between the two - the 800CFM units have a 'bump' in the venturi ring, and the 750 ones don't (but have a smaller venturi). Throttle plate diameters will be the same regardless.
 
A

Anonymous

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May not be exactly the same, but I have a Rochester 2 bbl "VariJet II" off a 78 chev 250 with the integrated head. The front butterfly is smaller than the other and I seem to remember it being progressive. I will try to verify that tomorrow.
Hope that helps.
Lee
 

CZLN6

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Howdy Back Lee:

That's the one I was looking for. I believe it is basically the right or left half of a QuadraJet. Making it a two stage, progressive two barrel. You've relite that candle. I'm off on another search. Thanks.

Adios, David
 
A

Anonymous

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I think its the same carb that was used on the chevette and the early 2.2 chryslers and maybe the late pintos
 

jamyers

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Aha! Rochester VariJet was used on the Chevy Citations w/ the 2.8 V6, circa 1980.

And yes, it's a progressive 2-bbl. My bro-in-law had one (in a Citation), and liked both the car and carb.
 

fmartin_gila

Well-known member
The Progressive 2 barrel as used on the Pinto is a reversed Weber 32/36, and is a very adaptable carb, as is the 32/36.

Fred
 

MustangSix

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I once owned a 1979 Chevy Monza with a V6 that had a dual jet. It looked the same as that one. Basically the front half of a Quadrajet.

It should work fine on a 200.
 

xctasy

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The carb is also called the Varajet, and is French made half a 4M Quadrajet. It has been used on 1892, 2838 and 3294 cc General Motor Holden L4 and L6 OHV engines and the European J car Family II 1596 cc OHC 4 cyl engines from late 1978 to 1988. Its an amazing carb, but a little difficult to calibrate because of the a)hanger enrichment and b) rod selections. Jetting probably has to be sourced from RRP (Rochester Re Productions) approved sources, with the V6 and V8 jets too big for these carbs, or getting a jewler to recut a stock small jet to the bigger sizes with the right internal finish, and main hole and chamfer required to ensure the right flow. Jets are close limit, and carfully calibrated for each FMV/EPA/CARB/or ADR aproved engine combination.

Most of the hard performance work for an I-6 engine was done with the standard 114-121 hp carb applications for any GM 2.8 V6, GMH 2.8 and 3.3 L6. Holdens Aussie engines were very different, 76/78/80 hp in the 1892 cc ohv four, the J car 1596 cc 85 hp engine and 102, 114 and 121 hp in the 2838cc and 3294cc. The Rochester Varajet carb on ohv engines was a replacement for earlier single barrel Stromberg carbs, and yielded an extra 10 hp with ease, as well as a massive improvement in fuel economy. On these engines, there were porting changes and ignition system upgrades as well, but emissions were getting harder to pass each year, and 10 hp and about 1 second off the quater mile was a pretty good indication.

In terms of performance, they are neck and neck with the ADM34 carbs used in the Fiat Spyder/131/132 and the brace of 32/36 versions (Holley Weber 5200, 5210, 6500, the Bressel or Weber DGAS 32/36 or Weber DFA 32/36).
 
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