oldsfever

I have a 69 Cutlass with the stock 350. It has the original Rochester dual jet that is in serious need of a rebuild. Does anyone still run one of those? Or is it better to swap and get a 4 barrel? I'll admit I'm weak whenit comes to carburetors and would like to keep it stock.

Oldsguy

If everything is stock there is really no reason to go with a 4 bbl carb. Once you take the first step it turns into a long walk.........

That dual jet is basically a quadrajet without the secondaries. There are rebuild kits available or you might contact Danny Sarvis (70Wcars) he rebuilds carburetors.

oldsfever

Thanks for the response. I am trying to keep it stock as I went down the other road with my first one and ended up not liking it very much.

69Rman

Not sure if this one I have here is the correct one or not, but you are welcome to it if it would work for you.
It as a pretty clean looking one I took off of a '72 350 that was in a '68 Cutlass S
Been sitting for quite some time, but is very clean and free moving.
part number stamped on it is 7029156
Under that is what I would think wold be a date code.
It is 111 6 1
Possibly a re-manufactured one though, there are a couple of stickers on it but they are not legible though.
You can have it for $20 if it would work.
PM me if interested and I will forward pics.
Duane

A72CUTLAS

I have a 2bll that is a 6-7 year old rebuild I bought from O'Reillys Auto Parts here in OKC after the originals base plate cracked. I didn't have any trouble out of it, I just swapped to a Quadrajet setup about 6mos ago. Here are a couple pics of it. I wish I could remember how to post 'em in the message, but I'm getting old I guess.

As for price, I'll give you the same deal 69Rman said, $20 plus shipping> Or if you're ever on this side of the Red River you could pick it up.

BILL DEMMER

a '69 dual jet is nothing like a quadrajet, it is much simpler.
you can rebuild this carb. yourself, it's not hard at all.

or...

www.sparkyscarbs.com


bill

oldsfever

Thanks for the replies and offers. I have decided to rebuild it since, after taking it off, it doesn't look like there is much to it. I might be contacting a couple of you if something goes wrong and heading north across the red river. The kit is suppose to be in today so my weekend is planned.

rocketraider

Uh, pardon me for living, but isn't DualJet that funky emissions carb used in late 70s?

I think what oldsfever has is actually Rochester 2 Jet. Simple carb to rebuild in any case.

oldsfever

Nope, it's says Dual Jet on top of the carb and the part number matches with what I've researched. So far, so good on the rebuild though. It's taken apart.

Run to Rund

The 2 barrel available in 1969 was a 2GC meaning a two jet (2G) with choke. The emissions/economy Dual Jet came in 1976 and if your intake manifold fits it, the manifold also has egr and of course is not original. Maybe the whole engine is later model.

oldsfever

It definately sounds like y'all know a lot more than I do so I won't argue the point. It will give me something to look into when I rebuild it in the next year or two. For now, I just want to get it put back together and the car to start.

Thanks fo the input and info., it is all appreciated as I learn my way around this car.

BILL DEMMER

i would strongly recommend a new float and fuel filter.


bill

BILL DEMMER

you're thinking of the dualjet 200/dualjet 210


bill

Oldsguy

Well please let us know what happens after you rebuild the carb.

oldsfever

I gave in and took it to a local shop but he finished the rebuild last night. I'm not the best at carburetors and didn't want to be the sourcee of more problems. Hopefully I'll get it back on today but my Dad got put in the hospital yesterday and we'll have to see how it goes. I'll take a picture of the carb just to let everyone see what I've been trying to explain.
Thanks for all the response and advice.

MDchanic

Sorry to hear about your dad. I hope all goes well.

I just wanted to weigh in with an answer to your original question.

First, there is absolutely no question that the DualJet was not made until the late '70's, so it cannot be original to your car.
The Rochester 2-Jet was the standard sixties / early seventies 2-barrel, without any doubt.
The DualJet is essentially the front half (primaries) of a QuadraJet, which is an excellent carb. The design allowed GM to save a bundle by using a lot of the same internal parts for both carbs. The DualJet has the same bolt pattern as a QuadraJet, just without the big secondary bores, and uses a unique DualJet intake manifold (which will have an EGR bore because it's from the late seventies). It cannot bolt up to a 2-Jet manifold.

The DualJet looks like the front half of a Quadrajet, has all the same connections in the same places, and has an airhorn opening (seen through the hole in the middle of the air cleaner) that is D-shaped.
The 2-Jet is boxy-looking and has a round airhorn opening, like in the photos from other posters above.

Now, on to my answer...

When I bought my '70 Chevelle in 1980, it had a CGC 350 in it from a '71 Impala. This was a 2-barrel, low compression motor rated (generously) at 245hp. Being a kid, I wanted to make it go faster, but didn't have any money to, say, actually buy a big block like the one that had come in it originally, so, like every other kid, I scrounged up a QuadraJet manifold and a carb from a '69 350, and you know what? It didn't run as well as it had before, and was no faster. It wasn't a big difference, so I didn't change it back (too embarrassing to admit it had a 2-barrel), but now I wish I hadn't left that 2-Jet, manifold, and air cleaner to rot on the side of the garage. Yes, I still have the car, and I still haven't sprung for the big block (though the build sheet showing a 454 call to me in my sleep).

2- versus 4-barrel was a sign of increased power in the sixties because the factory only put them on high-compression motors that were distinctly more powerful. On a motor that can't use the extra flow, they are useless, though. The big difference between a 2 and a 4 barrel carb (aside from technical differences related to individual designs) is that a 4-barrel will flow more air. You need more air flow if your engine is either very large in displacement, revs very high, or both. Otherwise, you don't. Carbs are rated by air flow in CFM (cubic feet per minute), and you can calculate the air flow of your motor very roughly by halving the displacement (a four stroke cylinder only take in air one out of every two revolutions), and multiplying it by the maximum RPM you will realistically use (in reality, since the cylinders' ability to completely fill up depends on the cam and the flow characteristics of the engine, the number will be less than the 100% fill we are assuming here).
So, for a 350 at 5,000 RPM, we get 175 x 5,000 = 875,000 cubic inches of air per minute, which is 500 CFM. For a more realistic top end for most sixties and seventies high-torque, non-high-performanace motors, you can choose 4,000 RPM, and get 400 CFM

Now, if you look at the specs for most 4-barrel carbs, we're talking about 650 or 750 CFM, so you can see how that extra capacity is completely unused.

I think you'll be happy you stuck with the 2-barrel.

Hope this helped...

- Eric

oldsfever

Thank you. Yes, that explanation helped tremendously. Now when I use it, I’ll sound like I know something instead of being just another buffoon (LOL).
Let me apologize to everyone that has commented on the model of the carburetor. When I removed it, I wrote down the model number and other information along with what was stamped on the top, I wrote down Dual Jet when it actually said 2 Jet. Why, I don’t know. I must have had dual jet on my mind from something I read. So Rocketraider, you were correct and I am so glad I didn’t argue with anyone as I hate eating more crow than I already am.
The rebuild went great, new float, all new vacuum lines, etc. and it went back on much easier than it came off. I primed it and it fired right up. I took it for a spin and it was idling a little rough but with a couple turns of the screws, it settled down and runs better than I thought it would. No leaks, smells, or scary noises. I went out this morning after it sat all night and it fired up without touching the accelerator. I’m a happy man right now.
I appreciate all of the comments, suggestions, and corrections. It keeps me honest and I learn something every time.
Now it’s on to replacing the rusted, leaking transmission cooling lines. Should be a piece of cake (Famous last words).
Take care!

Oldsguy

Eric, thanks for that complete explanation. I guess I was a little terse in my statement.

Run to Rund

Two barrels are rated at 3" vacuum because back when it started, that was the vacuum a typical V8 pulled through one at full power. 4bbls were rated at 1.5" for the same reason. Using the 4 bbl scale, a 2-jet is usually in the 250-300 cfm range (depending on the venturi size, such as 1-3/16" or 1-5/16"). The Quadrajet is pretty advanced with its air valve so an engine that does not "need" 750 cfm simply does not pull the air valve all the way open, and nothing is lost.

MDchanic

You're welcome. I wouldn't have responded, except that I had a personal experience with this exact question, which I thought might make my answer more real.

- Eric