8683jb
Contributor
Posts: 123
Reg: 09-06-13
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01-30-23 12:21 PM - Post#2853927
I have a Rochester 4GC carburetor with a tag attached reading 7020022, which I think is for about a 1962 Chevy. But the carburetor has an idle compensator valve. Isn't that for a later application? I'm thinking the tag may not be correct for this carburetor. Does someone know what year the compensator valve would have first appeared on the 4GC carburetors?
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 dgstarr
"5th Year" Silver Supporting Member
Posts: 388
Loc: Portland, OR
Reg: 04-16-13
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01-30-23 06:09 PM - Post#2853936
In response to 8683jb
1962 passenger, 327/250hp, AT, AC, (Late after Dec 1961). The B indicates the second series, the D2 indicates April 1962
The hot idle compensator was commen on AC cars. My 62 327/300hp with AC has one on the Carter AFB carb.
Edited by dgstarr on 01-30-23 06:17 PM. Reason for edit: No reason given.
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8683jb
Contributor
Posts: 123
Reg: 09-06-13
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01-31-23 01:52 PM - Post#2853963
In response to dgstarr
Thanks for all that info. I appreciate it!
Edited by 8683jb on 01-31-23 01:52 PM. Reason for edit: No reason given.
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Tony1963
Frequent Contributor
Posts: 2199
Loc: Orlando Florida
Reg: 07-09-18
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01-31-23 05:24 PM - Post#2853966
In response to 8683jb
Somewhere I have a book written by Doug Roe and he was an engineer for Rochester Carburetors back in the day.
I seem to recall that the hot idle compensator was installed on vehicles that had AC and also those that were destined for hot climates.
I'd recommend finding this book as it has tons of great information.
https://www.amazon.com/Rochester-Carburetors -Revis...
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8683jb
Contributor
Posts: 123
Reg: 09-06-13
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01-31-23 06:07 PM - Post#2853967
In response to Tony1963
Thanks, Tony! I'll check it out.
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 docjns1
"3rd Year" Gold Supporting Member
Posts: 329
Loc: upstate NY
Reg: 11-12-19
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01-31-23 07:13 PM - Post#2853968
In response to dgstarr
Ditto my '65 non AC with the AFB.
Additionally the 1962 Chevy service publication for servicing the AFB makes note of the hot idle compensator and its purpose/operation, but no mention of it specifically for AC equipped cars. Presumably the 4GC set up would function in the same manner and/or circumstances.
Steve
*********
'65 Impala SS, Crocus Yellow/blk
327 / 300 L74
M11 3 on the tree
12 bolt 3.31 open dif |
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dgstarr
"5th Year" Silver Supporting Member
Posts: 388
Loc: Portland, OR
Reg: 04-16-13
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01-31-23 09:44 PM - Post#2853983
In response to docjns1
Chevrolet by the Numbers, by Alvin Colvin, indicates that the AFB and WCFB with AT trans were the same for AC and non AC cars. The Rochester 4GC, starting in 1962, were a different part number for AC cars.
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 Carl1962
"11th Year" Silver Supporting Member
Posts: 1495
Loc: Bungendore Australia
Reg: 04-01-10
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02-01-23 12:52 AM - Post#2853986
In response to 8683jb
My 1962 Impala with 327 (250hp) and factory air has exactly the same carburetor (7020022) with the same compensator.
Cheers, Carl.
1962 Anniversary Gold SS Impala Sports Coupe
1962 Anniversary Gold Impala Register
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8683jb
Contributor
Posts: 123
Reg: 09-06-13
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02-01-23 04:12 PM - Post#2854019
In response to Carl1962
Thank you guys for the help. Carl - since I posted this I noticed this carb doesn't have the port on the forward right side of the throttle plate for the vacuum advance. Does yours have that?
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Carl1962
"11th Year" Silver Supporting Member
Posts: 1495
Loc: Bungendore Australia
Reg: 04-01-10
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02-02-23 12:04 AM - Post#2854039
In response to 8683jb
Thank you guys for the help. Carl - since I posted this I noticed this carb doesn't have the port on the forward right side of the throttle plate for the vacuum advance. Does yours have that?
There's no vacuum advance port on the front of my carb, the vacuum advance comes from a hollow stud at the back LH side.
Cheers, Carl.
1962 Anniversary Gold SS Impala Sports Coupe
1962 Anniversary Gold Impala Register
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8683jb
Contributor
Posts: 123
Reg: 09-06-13
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02-02-23 07:12 PM - Post#2854074
In response to Carl1962
Thanks again so much, Carl. I guess the tag number on this one is right then. I sure appreciate the help!
Jon
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WAHELTON
Newbie
Posts: 3
Reg: 03-26-22
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02-08-23 06:15 AM - Post#2854255
In response to 8683jb
to further the discussion, my 1960 Impala with 348. powerglide, and factory AC has the 4GC with the idle compensator. My tag is gone but the book show part 7013012 replaced by 7015012. Non AC cars were 7013006 without the idle compensator. The 283 used 7013010 w/Air Cond and 7013004 without.
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