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Author Topic: New CRG Research Report - First-Gen Carburetors  (Read 10415 times)
9T4Z
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« Reply #15 on: December 08, 2007, 05:00:46 PM »

Great report ED. Thanks from all of us north of the border.

I'll second that!
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Gary 9T4Z

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69 Pace Car, 70RS,91Z,91RS
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« Reply #16 on: December 08, 2007, 11:33:30 PM »

Ed -

I had a chance to check the "numbers" on my '68 Z/28 Holley carburetor today.  I'm glad to report that all the "numbers" are as you state in your report!  The date code is 822.

Paul     
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JoeC
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« Reply #17 on: December 15, 2007, 11:44:59 PM »

nice job and thanks to all who worked on the carburetor report

have not seen those 2 BB for a long time
In the mid 70s I had a daily driver 68 El Camino 350 4sp and was trying to improve fuel mileage.
Replaced the 600 Holley with the larger 2 BB on a home made adaptor plate on a alum intake and home made manual choke setup.

Once I got the jetting right it Worked pretty well. Was very smooth like a fuel injection car with no secondarys to kick in

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KurtS
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« Reply #18 on: December 27, 2007, 07:31:00 PM »

The article had a minor revision and a couple of errors were corrected and photos credited.

Anyone have a L65 (69 350/250hp) 2bbl carb? We'd like to confirm one detail. Smiley
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Kurt S
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opelitis1
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« Reply #19 on: February 28, 2008, 06:33:22 AM »

Hi Kurt S.!!!  Do you have a number on the 2bbl L65 carb???  Maybe I can be of assistance...  Ted
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KurtS
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« Reply #20 on: February 28, 2008, 06:04:24 PM »

Ted,
The article lists all the part numbers for the L65 carb (though the broadcast codes for the AC models, 115 & 116, are lacking).
The detail: is the fuel line inlet located on the side of the carburetor, like the one pictured here, http://www.camaros.org/images/carb/carb_7029112.jpg. Or is it on the front?

Thanks!
Kurt
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Kurt S
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« Reply #21 on: February 29, 2008, 08:10:16 AM »

Good morning!!!  Carb I have is 7029114  281 DD 81   front inlet.  Ted
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KurtS
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« Reply #22 on: February 29, 2008, 12:04:41 PM »

Ted,
That means we need to change that in the article.
Can you send me a good overall pic of the carb?

Thanks for the help!
Kurt
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Kurt S
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rich69rs
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« Reply #23 on: March 03, 2008, 11:31:27 PM »

Fuel line in front of the 2Bbl suggests the larger SAE 1-1/2" version of the 2GV vs. the smaller SAE 1-1/4" version of the 2GV used on the base 327/210 and 307/200 engines.  Consistent with what I've observed on 2 Bbl applications on 327/235 Hp engines on full size Chevys in 1969 which also got the SAE 1-1/2" 2GV carb.  Makes sense that the SAE 1-1/2" 2 Bbl would also get used on the L65 (350/250 hp) engine.

In addition to the reference listed previoulsy, 1965-69 Chevrolet by the Numbers also has the following information:

7029114 for:  "Passenger, Chevelle, Nova, Camaro; 350/250 hp with automatic trans., no A/C"

Also listed are:

7029113 for:  "Passenger, Chevelle, Nova, Camaro; 350/250 hp with manual trans., no A/C"
7029115 for:  "Passenger, Chevelle, Nova, Camaro; 350/250 hp with manual trans. and A/C"
7029116 for:  "Passenger, Chevelle, Nova, Camaro; 350/250 hp with automatic trans. and A/C"

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. 

If the carb has this feature, it is easily noted on the back (firewall) side of the carb base 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.
« Last Edit: March 03, 2008, 11:46:34 PM by rich69rs » Logged

Richard Thomas
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« Reply #24 on: March 04, 2008, 12:50:04 PM »

Good afternoon Rich/Kurt!!!  I have the 7029114 sitting in front of me and it does not have the Hot Idle Compensator on the rear of the carb body...  Not sure if this is of any importance but, the main venturi cluster is numbered 36245...  I  do not see an identification circle on the rear of the carb as  the Q-Jets have...  Maybe 2-jets did not this identification ...Huh

Kinda wish at this point in time,  I had not asked the "stock car" person  to "have a go" at the carb...   Ted
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KurtS
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« Reply #25 on: March 05, 2008, 03:21:30 PM »

Fuel line in front of the 2Bbl suggests the larger SAE 1-1/2" version of the 2GV vs. the smaller SAE 1-1/4" version of the 2GV used on the base 327/210 and 307/200 engines.  Consistent with what I've observed on 2 Bbl applications on 327/235 Hp engines on full size Chevys in 1969 which also got the SAE 1-1/2" 2GV carb.  Makes sense that the SAE 1-1/2" 2 Bbl would also get used on the L65 (350/250 hp) engine.

That's why I asked that question. The service manuals kinda indicate it was the smaller 2GV, but I suspected different.

Ted,
Your carb isn't for AC. Smiley
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Kurt S
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