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Username Post: AFB Carbureator        (Topic#369067)
dgstarr 
"5th Year" Silver Supporting Member
Posts: 339
dgstarr
Loc: Portland, OR
Reg: 04-16-13
07-28-22 08:00 PM - Post#2845079    

62-64 300 hp 327 engines all came with Carter AFB's.
The PG cars had a different model number carb than the MT cars. My question is why were they different, and what was the actual difference?



 


Tony1963 
Frequent Contributor
Posts: 1597

Loc: Orlando Florida
Reg: 07-09-18
07-29-22 02:00 AM - Post#2845091    
    In response to dgstarr

The standard carburetor was the 4GC. It was a Rochester Products unit that worked well.

From what I have heard, the other carburetor had a slight increase in flow so rather than tinker with the Rochester unit, the other carburetor was installed.

Nothing magic here.

People fear change because it threatens what they know, or what they claim to know.


 
DonSSDD 
Silver Supporting Member
Posts: 7824
DonSSDD
Loc: Nova Scotia, Canada
Reg: 08-21-01
07-29-22 03:31 AM - Post#2845095    
    In response to Tony1963

The Carter had a larger cfm than the 250hp 4gc. Other than a unique 4gc on the 409, all the higher hp GM engines of this era had a Carter until a Holley was used in later vettes.

I think the difference between auto and manual setups had to do with the kickdown setup on automatics plus mechanical differences needed due to the “pause” in carburetion that happens on gear changes on the manual. The auto never totally unloads as your gear change happens.

You may find a good explanation by reading on The Carburetor Shop site , Jon posts here as carbking, he may see this and give you the real story.

https://www.thecarburetorshop.com/

Don

63 Pontiac Parisienne Sport Coupe(CDN Chev mechanically (409, 4 speed),62 Bel Air SC (sold), 59 El Camino (sold), 62 Bel Air SC(sold), 63 SWC Vette (sold),
Member #2194


 
carbking 
Senior Member
Posts: 1563
carbking
Loc: Missouri
Reg: 06-14-03
07-29-22 06:07 AM - Post#2845101    
    In response to DonSSDD

Without pulling the prints, and going from memory:

1962:

S/T 3269s
A/T 3310s

1963:

S/T 3461s
A/T 3460s

1964:

S/T 3721s
A/T 3720s

1965:

S/T 3721sa
A/T 3720sa

Service replacement

S/T 3721sb
A/T 3720sb

GENERALLY, there will be a slight calibration difference from S/T to A/T to compensate for the fluid coupling energy losses in the torque converter used with A/T. This is difficult to see at times because it may seem the S/T carbs are richer if one just looks at jetting, and fails to look at air bleeds.

In 1962, there is an early and late production for both carbs, with a significant change in the primary throttle shaft arm.

The 1963 carbs had a major reconfiguration of the automatic choke/fast idle circuit from the 1962 (different choke housings, different fast idle cams, etc.)

The 1964 carbs had minor changes in how the castings were machined.

The 1965 carbs (with the "sa" suffix) got a calibration change from the 1964 carbs (with the "s" suffix).

The service replacement carbs (with the "sb" suffix) got another slight calibration change from the carbs with the "sa" suffix.

Just a good example of two manufacturers (Carter and Chevrolet) trying to improve on their products.

Jon

Good carburetion is fuelish hot air!

The most expensive carburetor you will ever buy.....is the incorrect one you attempt to modify!

If you truly believe "one size fits all", trying walking a mile in your spouse's shoes!


 
Mel Foye 
*VIP* Original Founding Member Group
Posts: 5484
Mel Foye
Reg: 09-29-00
07-30-22 11:08 AM - Post#2845156    
    In response to carbking

Jon I think you are wrong. They did not make the AFB because it was better they made it so their 401-Ks would be fatter, they could eat more themselves and get bigger bonuses.
I am sure I read that some where. Take care. :laugh : Mel



It Was On Fire When I Laid Down.


 
junky 
Valued Contributor
Posts: 3873

Loc: Northeast CT
Reg: 06-27-10
07-30-22 12:10 PM - Post#2845159    
    In response to Mel Foye

  • Mel Foye Said:
Jon I think you are wrong. They did not make the AFB because it was better they made it so their 401-Ks would be fatter, they could eat more themselves and get bigger bonuses.
I am sure I read that some where. Take care. :laugh : Mel



You must be quoting Tony1963! His dribble is like poison ivy, it spreads, and just reading it makes you want to take a cold shower to stop the annoying itch known as Tony1963!

Never argue with an idiot. He'll drag you down to his level, then beat you with experience.


 
japete92 
"8th Year" Silver Supporting Member
Posts: 2025
japete92
Loc: No. Virginia
Reg: 01-18-13
07-30-22 01:01 PM - Post#2845160    
    In response to junky

  • junky Said:
  • Mel Foye Said:
Jon I think you are wrong. They did not make the AFB because it was better they made it so their 401-Ks would be fatter, they could eat more themselves and get bigger bonuses.
I am sure I read that some where. Take care. :laugh : Mel



You must be quoting Tony1963! His dribble is like poison ivy, it spreads, and just reading it makes you want to take a cold shower to stop the annoying itch known as Tony1963!




Junky,

Here's what 'expert' 'Tony1963' has to say (in his own words) about his experience and 'qualifications':

'I never worked for GM and instead, pursued a career in the financial side of healthcare. Here in the US healthcare was $4.1 trillion dollar industry in 2020 and a great place to earn a fantastic living.

While I do have an interest in cars, and was a dealer for 20 years, I prefer professional work in the financial side of healthcare.'


AND, from his bio (again his own words):

'I am a healthcare finance executive with a passion for automobiles. When I lived in Alabama, I owned a car dealership that specialized in Mercedes, Volvo and BMW. We also sold many low-mileage ultra-clean Corvettes.

The dealership also sought the unusual vehicles and had a loyal following. Moving to Florida, I sold the dealership in 2018. However, my passion for vehicles continues.'

Claims to have owned a used car dealership from 1998 to 2018 (20 years).

My take? A 21st century 'wanna be' 60's/50's car guy. No experience and no credibility. He thinks his income makes him 'qualified' to comment/advise on topics he knows 'jack' about.

If the info was not misleading to folks who are new to the hobby of 50/60 cars, it could simply be ignored. To inform the new folks, a light needs to be shown on this charlatan ( or quack, sham, fraud, fake, imposter, or any other synonyms).

Pete




 
Tony1963 
Frequent Contributor
Posts: 1597

Loc: Orlando Florida
Reg: 07-09-18
07-30-22 01:10 PM - Post#2845161    
    In response to japete92





People fear change because it threatens what they know, or what they claim to know.


 
docjns1 
"2nd Year" Gold Supporting Member
Posts: 291
docjns1
Loc: upstate NY
Reg: 11-12-19
07-31-22 07:37 PM - Post#2845260    
    In response to carbking

Since my 65 runs the 3721SB I'll assume your memory is correct regarding the other years as well Jon! And does the SB calibration presume to be a 'better' carb than the SA, re: performance and/or fuel economy?

Oh, and all the talk about those making their 401k's fatter...from someone in the 'financial' end of the U.S. health care business? Methinks they're not working to help us control costs and lower premiums, etc. But then again, I'm not looking to always have the last word!

Steve
*********
'65 Impala SS, Crocus Yellow/blk
327 / 300 L74
M11 3 on the tree
12 bolt 3.31 open dif


Edited by docjns1 on 07-31-22 07:39 PM. Reason for edit: No reason given.

 
carbking 
Senior Member
Posts: 1563
carbking
Loc: Missouri
Reg: 06-14-03
08-02-22 05:40 AM - Post#2845343    
    In response to docjns1

Steve - the "sb" calibration was the latest calibration.

GENERALLY, carburetors designed for O.E. use would be optimized for driveability.

Jon

Good carburetion is fuelish hot air!

The most expensive carburetor you will ever buy.....is the incorrect one you attempt to modify!

If you truly believe "one size fits all", trying walking a mile in your spouse's shoes!


 
docjns1 
"2nd Year" Gold Supporting Member
Posts: 291
docjns1
Loc: upstate NY
Reg: 11-12-19
08-04-22 01:22 PM - Post#2845441    
    In response to carbking

thanks!

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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