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Old 11-09-2011, 07:38 AM
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☺What's this on my carb?????????

What is this for, on the back of my Rochester 2 barrel carb?

Also cant find any information on what year carb this is or what it fits.


It's on a 1963 Impala now but my manual says I need a 7023008 number carb.

HELP

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Old 11-09-2011, 09:13 AM
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I think this is what you are looking at.

http://www.highperformancepontiac.co.../photo_04.html
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Old 11-09-2011, 09:35 AM
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lmsport
You might be right but that says for a Q Jet carb.
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Old 11-09-2011, 12:24 PM
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I think its a Rochester carb feature that was used on two and four barrels. All older Qjets have the casting to accommodate the feature but many do not have it. Must have been specific to certain models. Take the plate off and see if the is a bimetal strip with a circular vale attached to one end underneath.
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Old 11-09-2011, 12:52 PM
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DON"T TOUCH IT!!!The world will end!!
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Old 11-09-2011, 12:53 PM
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Hot air compensator. It leaned out the mixture caused by heat evaporating/vaporizing the fuel when the carb was heat soaked.

EDIT saw the link- it's the same regardless if it's on a Q-jet or a 1 barrel. For a few years carbs continued to have that cast into the carb body after it was no longer being used. The passages weren't opened up and the screw holes weren't threaded on these later carbs.

The casting number shown on the side of the carb will be of no real help- because it's a casting number, not the carb number. The carb number would have been on a metal tag under one of the air horn screws.

Last edited by cobalt327; 11-09-2011 at 01:06 PM.
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Old 11-09-2011, 01:14 PM
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Tag says Auto Line products C937
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Old 11-09-2011, 01:32 PM
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Quote:
Originally Posted by impalaman63
Tag says Auto Line products C937
Unfortunately that's of little or no use to you, it's a rebuilder tag that doesn't show the original carb number, just 'their' part number. This is so a variety of vehicles can be serviced by fewer part numbers. And even if this outfit is still in business, the chances of them being able to cross reference their p/n to the original carb number is almost nil.

But except for having the tag for originality, all you really need to be concerned with is that the carb is 'correct' for your vehicle (right choke and linkage type, etc.) and that it's calibrated and adjusted correctly for your engine. When you rebuild it, you will be using the carb specs for your vehicle that are supplied w/the carb kit. Judging by the looks of the carb gaskets, I'd say it's been Gunked a few times. That will make the gaskets soggy on the outside edges like you see on yours.
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Old 11-09-2011, 07:32 PM
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I emailed the company and they said - It fits a 1963 Chevrolet with a 263 or 283 engine.
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Old 11-12-2011, 08:23 AM
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Found this information.

One of the main differences between Rochester 2GV carbs was the use of the "hot idle compensator" feature found on Rochester 2GV carbs designed to be used with factory A/C. If the application was a non A/C car, then the carb did not incorporate the hot idle compensator. So, for your application, be sure you find a 2GV either with or without the hot idle compensator depending on whether or not your car has A/C or not.

A Rochester 2GV with the hot idle compensator feature is easy to identify by looking at the back (firewall) side of the carb as described in the following from Carburetor Models 2G, 2GC, 2GV Service Manual 9D-3, May, 1973:

During prolonged idling in heavy traffic in hot weather, under-hood temperatures can exceed 200 degrees Farenheit causing severe percolation or boiling of fuel in the carburetor float bowl. With excessive heat, all fuel vapors cannot be eliminated through normal venting and some will be drawn into the carburetor bore and intake manifold resulting in over-rich idle mixtures. The rich mixture causes a rough idle and may even cause engine stalling. The Hot Idle Compensator is used on some 2G carburetor models to off-set the enriching effects caused by these excessive fuel vapors by supplying additional air to the intake manifold when idle air/fuel mixtures become rich due to temperature increase. The compensator consists of a thermostaticallycontrolled valve usually mounted in the area above the main venturi or at the rear of the float bowl. The valve closes off an air channel which leads from above the carburetor venturi to a point below the throttle valves.

The compensator valve is operated by a bi-metal strip that senses temperature. At a certain predetermined temperature, when extra air is needed to off-set the enriching effects of fuel vapors, the bi-metal strips bends and unseats a valve which uncovers the air channel leading from the carburetor venturi to below the throttle valves. At this time, just enough air is added to the engine
to offset the richer mixtures and maintain a smooth engine idle. When the engine cools and the extra air is not needed, the bi-metal strip closes the valve and operation returns to normal mixtures. Hot idle compensators are pre-set at the factory and require no adjustment. However, to insure proper idle adjustment, the valve must be closed when setting engine idle speed and mixtures. This can be done by using a screwdriver to press down lightly on the valve for those models with the valve located in the main venturi
area. On those models with the valve located at the rear of the float bowl, hold spring-loaded button "in" when making the
idle settings. If no button is available, remove idle compensator cover and using a screwdriver, press in lightly on the valve when making idle settings. Replace cover after completing idle adjustments.

Over the years, this is the type of distinction that has gotten lost when you go down to the local parts store and try to find a "correct" replacement carb. GM/Chevy designed variations depending on application and options. Now you will get "the one size fits all" story from the local parts house, assuming that they even offer a "replacement" carb. Clearly, "one size fits all" was not how GM/Chevy designed it.
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Old 11-12-2011, 12:23 PM
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Quote:
Originally Posted by impalaman63
I emailed the company and they said - It fits a 1963 Chevrolet with a 263 or 283 engine.
I don't know what they were trying to say- Chevy never made a "263", the SBC 262 and 267 came much later. In '63 there were 283 and 327 SBC engines, but the 265 had already gone by the wayside (at least in the US) and the 283 had taken over for it.
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Old 11-12-2011, 06:58 PM
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Quote:
Originally Posted by cobalt327
I don't know what they were trying to say- Chevy never made a "263", the SBC 262 and 267 came much later. In '63 there were 283 and 327 SBC engines, but the 265 had already gone by the wayside (at least in the US) and the 283 had taken over for it.
He said 63 Chevy. It could mean Chevrolet car, bus, truck, Canadian pontiac 261. It could mean 292, and them or he mistyped it. Relax a little.
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Old 11-13-2011, 02:39 AM
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Quote:
Originally Posted by mouse77
He said 63 Chevy. It could mean Chevrolet car, bus, truck, Canadian pontiac 261. It could mean 292, and them or he mistyped it. Relax a little.
Relax a little? Where the hell did that come from?

He "said" exactly what I quoted above- and there is no 263 Chevy engine- and more to the point, the info from the tag provided by the carb rebuilder is not relevant except to them. Just as I alluded to earlier- you cannot hope to get the exact carb number from them based on their rebuilder tag. And apparently you also cannot even get an accurate listing of what the carb fits.
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