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Old 04-03-2012, 08:22 AM   #1
duwem
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Simple Carburetor Replacement for Chevy 235?

I have a 58-62 vintage 235 in my pickup.

Have had nothing but problems with carbs since I bought it 2 years ago.

Always need to run with the choke partially on.

Rochester 1bbl.

Bought a rebuild kit, accelerator pump didnt match.

Bought a second carb, same accelerator pump as the first carb, so no dice.

Second carb runs a little better, but still need the choke on.

I also have an adaptor to a 2bbl, but not a good carb.

Is there a new single barrel that I can bolt up and get decent results?

Should I just go to a 2bbl, if so which one and from what vehicle.

This is a short term deal till I get my V8 in, so not looking to spend a ton of money or effort.
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Old 04-03-2012, 02:00 PM   #2
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Re: Simple Carburetor Replacement for Chevy 235?

Find a rochester 2GC, very bullet proof and easy to rebuild. Rebuild kits are readily available. I sold my stash to a Olds guy that was looking for parts carbs for his tri-power setup. Smaller Holley 2bll (not a 500 cfm but smaller) would work too. I had those on my VW and Mazda, once you get the jetting right they do well too.
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Old 04-03-2012, 02:07 PM   #3
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Re: Simple Carburetor Replacement for Chevy 235?

What vehicles did that come on?

Aside from some air leaks (interal to the carb, or external to the intake manifold etc), is there any reason why mine might not just need a jet drilled out on my current one so I can run it without the choke on?
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Old 04-03-2012, 03:00 PM   #4
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Re: Simple Carburetor Replacement for Chevy 235?

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Originally Posted by duwem View Post
What vehicles did that come on?

Aside from some air leaks (interal to the carb, or external to the intake manifold etc), is there any reason why mine might not just need a jet drilled out on my current one so I can run it without the choke on?
Exactly. I drilled the main jet in my Roch. model B on my 56 out to .062. It runs great now.
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Old 04-03-2012, 03:05 PM   #5
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Re: Simple Carburetor Replacement for Chevy 235?

What excatly is the jet, #14?
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Old 04-03-2012, 03:25 PM   #6
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Re: Simple Carburetor Replacement for Chevy 235?

No. Its #17. There is a number stamped on it. It is usually about 55-58 on 235. Sometimes the rebuilders guggle parts & you wind up with something from a 216. Increase it 2-3 steps at a time till it runs right.
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Old 04-03-2012, 08:11 PM   #7
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Re: Simple Carburetor Replacement for Chevy 235?

The jet in the first carb was a 58.

Second carb is on the truck, so I will have to pull it off or at least apart to check.

When you drilled yours out, did you notice it helped across the whole throttle range? Did it have any negative affects?
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Old 04-03-2012, 11:26 PM   #8
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Re: Simple Carburetor Replacement for Chevy 235?

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What vehicles did that come on?
Just about any GM 2 bbl engine from 55 to around 68 or so. Hot rod guys like them for the 3 deuce set ups. Original ones for the 3 deuce set ups only had a choke on the center one, other two are choke less and very rare. Here is one on a 235.
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Old 04-04-2012, 01:29 PM   #9
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Re: Simple Carburetor Replacement for Chevy 235?

Found on inline 6 or v-8 engines or both? Is a car one or truck one any different (mechanical vs heat/vacuum choke etc)?

Going to try drilling out the jet on my current one when I get around to tearing it apart, if that doesnt work then a 2bbl will be plan B. That adaptor on the left looks a lot like the one I have sitting in a box.
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Old 04-04-2012, 01:53 PM   #10
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Re: Simple Carburetor Replacement for Chevy 235?

If you have to keep the choke partially on to have it run that is often an indication of a vacuum leak. Is the hose running from the engine to the windshield wipers in good shape? A crack in it or a leak at the wipers could cause a problem.
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Old 04-04-2012, 01:58 PM   #11
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Re: Simple Carburetor Replacement for Chevy 235?

I capped that line off and there was no change, but I have not tried the start fluid trick on the whole intake manifold yet to look for other leaks.

Could be a leak in the carb too I would assume. I took the auto choke off and put on a mechanicl conversion kit (the $10 auto zone universal one), not sure if something with that vaccum line for the old choke needs to be capped off?
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Old 04-04-2012, 03:52 PM   #12
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Re: Simple Carburetor Replacement for Chevy 235?

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Originally Posted by duwem View Post
The jet in the first carb was a 58.

Second carb is on the truck, so I will have to pull it off or at least apart to check.

When you drilled yours out, did you notice it helped across the whole throttle range? Did it have any negative affects?
It solved the complete problem. Has a little bog when cold & runs great when waems up. That is a good indication that the mixture is about right.
This is not a substitute for some thing wrong. Make sure your float level is correct & the accel.pump is working.
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Old 04-04-2012, 05:40 PM   #13
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Re: Simple Carburetor Replacement for Chevy 235?

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Originally Posted by duwem View Post
Found on inline 6 or v-8 engines or both? Is a car one or truck one any different (mechanical vs heat/vacuum choke etc)?
I have not had 6 later than 58 so I do not know if they are on later models. Standard carb for mom and pop 283 and 327 engines. I believe cars and trucks have the same choke and throttle linkage setups, you will need to adapt both for the 235. There are two kinds of heat chokes, one uses a tube from the exhaust manifold, the other has an little house with a bi-metal coil spring that sits on the manifold and connects to the choke lever. Rochesters did not have electric chokes.

Take a look at this link http://carbkitsource.com/carbs/tech/...Jet-index.html
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Old 04-13-2012, 08:17 AM   #14
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Re: Simple Carburetor Replacement for Chevy 235?

On my Single Rochester.

When put the carb on last year, I took off the auto chock and hooked up a cable using auto zones univerial kit.

There is a steel line that goes from the bottom of the carb (numbers 4 and 42on that carb parts breakdown I posted above) to the area where the choke was.

Last night to look for any air leaks, I sprayed starter fluid all around the intake and carb while running and the only place it made any RPM difference was if I shot it at that plastic cap for the choke adaptor.

Do I need to seal this metal line off?
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Old 04-13-2012, 04:52 PM   #15
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Re: Simple Carburetor Replacement for Chevy 235?

Put a vacuum guage on your carb and see what you are reading and try to get the highest reading possible check all openings on the carb and see if if you can get everything sealed uo except the line to the distributor, vacuum advance must be working
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