68 Rochester 2BBL Carburetor 2GV - Team Camaro Tech
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post #1 of 7 (permalink) Old Jan 24th, 17, 06:46 PM Thread Starter
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68 Rochester 2BBL Carburetor 2GV

I've got a 68 327/210hp with the Rochester 2GV carburetor. My question is why do some have the vent hole over the fuel bowl and some don't. What was the purpose of the hole and the mechanism that closes it off? Were the different carburetors based on build date of the car?

Without vent hole:



With vent hole:


'68 RS
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post #2 of 7 (permalink) Old Jan 24th, 17, 07:27 PM
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Re: 68 Rochester 2BBL Carburetor 2GV

I used to be asked the same question over the parts counter and I think the correct label was a tempature compensator? Really never made sense as the bowls normally had an angled vent tube. Seen some with a little vent top bell. Probably not the final answer.

Don
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post #3 of 7 (permalink) Old Jan 24th, 17, 08:26 PM Thread Starter
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Re: 68 Rochester 2BBL Carburetor 2GV

Thanks Don. I assume the one with no vent is the original carb for my car but I don't know how to make sure.

'68 RS
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post #4 of 7 (permalink) Old Jan 25th, 17, 05:18 AM
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Re: 68 Rochester 2BBL Carburetor 2GV

Hmm, the fuel bowl vent is inside the venturi opening (on both carbs), but the small hole is for something else. 69 q-jets had a similar hole with a rubber seal on a spring loaded lever. Might be if things got too hot (like vapor lock), it would open and relieve internal pressure. I agree, for 68, use the non-vented version.
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post #5 of 7 (permalink) Old Jan 25th, 17, 06:11 AM
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Re: 68 Rochester 2BBL Carburetor 2GV

Quote:
Originally Posted by KevinW View Post
Hmm, the fuel bowl vent is inside the venturi opening (on both carbs), but the small hole is for something else. 69 q-jets had a similar hole with a rubber seal on a spring loaded lever. Might be if things got too hot (like vapor lock), it would open and relieve internal pressure. I agree, for 68, use the non-vented version.
On a Quadrajet, that is an idle vent. The spring lever holds it open at idle and it closes when the throttle lever moves off idle. It helps prevent stalling at idle with a hot engine. You can see a similar spring valve in the second picture on the 2 bbl.
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1967 RS 327/275hp
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post #6 of 7 (permalink) Old Jan 25th, 17, 06:17 AM
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Re: 68 Rochester 2BBL Carburetor 2GV

Quote:
Originally Posted by trland View Post
On a Quadrajet, that is an idle vent. The spring lever holds it open at idle and it closes when the throttle lever moves off idle. It helps prevent stalling at idle with a hot engine.
Having my nose in parts books in my early years causing me to think the proper name of this vent plug as an "altitude compensator" ?
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post #7 of 7 (permalink) Old Jan 25th, 17, 08:44 AM Thread Starter
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Re: 68 Rochester 2BBL Carburetor 2GV

Quote:
Originally Posted by trland View Post
On a Quadrajet, that is an idle vent. The spring lever holds it open at idle and it closes when the throttle lever moves off idle. It helps prevent stalling at idle with a hot engine. You can see a similar spring valve in the second picture on the 2 bbl.
My old 68 (original owner - early build) had the vent hole with the spring but my current 68 (medium to late build) doesn't have the vent hole. It appears to be original but you never can tell with an old car. I'm the second owner of my current 68 but who know what the first owner did in all those years he owned it.

'68 RS
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