[GP65AT]

Hello,

after the season is almost done for this year, I would like to do some service work on my Grand Prix.
One big task would be to overhaul the carburator becaus the choke is annoying me very often.
The little piston which is moved by the round spring under the black platic cap is clamped by dirt or condensation water or what ever, and the fast idle will stay very high the warmer the engine gets.

How can I find out which type i have mounted when there is no tag number on it.
The only two numbers I could find are 1694 and 1565. But this seem to be part numbers ob the body and the cover of the carb?!

Maybe you can give me some tips how I can find it out?
Or would it be better to replace it with an Edelbrock or Holley (what I would not prefer because I would like to repair the original one)?

Thanks a lot
with best regards
Stefan

[jdh421]

there are casting numbers cast into the side of the lower part and also on the top of the top plate. they will be like this (x-xxxx) x being a number. that can help to identify the unit. pictures can help too.

[Poncho60]

If the car is original, the carb should be a Carter AFB......which is much preferred over the aftermarket replacements i.e. Edelbrock etc clones.....according to most people.

[GP65AT]

Thanks,

yes it is a Carter AFB, I have fogotten to write this.
But I would like to know which exact type it is to buy the right spare parts.

The only number that would fit would be 6-1694 , but I can not really find right fitting spare parts?

So see attached pictures, maybe they will help.

Thanks
Stefan

[scld1354]

From http://www.thecarburetorshop.com/Carburetor_ID.htm. The owner of that shop is a member here (carbking).

"AFB Series – (4 barrel) (1957 – 2001) metal tag: also some units stamped on edge of flange, some units stamped center of bowl in rear, some units stamped along bowl – airhorn seam in front, some units NOT stamped (tag only)"

Depending on the year of your can, and if it's the original carb, you can use this LIST from the same webiste to get an idea of what carb your car has.

For example, for a 1965 car with a 389, auto trans, and a 4bbl, if you look about half-way down the page, you'll see it came with a Carter AFB #3896. The rebuild kit from that site would be the last column (#548)

[63gpman]

It looks like the correct 1965 AFB from what I am seeing. It has the same bowl and airhorn castings as my 3895S carb from 1965. The castings may have been made for many years though.

Best to get a kit to rebuild this carb. These Pontiacs love the correct OE carbs.

[Deadhead]

Tons of kits for these on E-Bay. Very easy to do. Pretty much all Carter 4bbls from '63-66+ take the same kit. Do a search for your year pontiac and carb kit, and you should find what you need. If I remember right, there are not many or any helpful #s on the carb if it has no tag on it.

[63gpman]

Here are the specs on a 3895S carb. Confirm you have the same and order a kit for that. Also, if you reach out to carb king, he should be able to confirm that it will work for you.

Carb # 3895S
Year 1965
Low speed jet size 0.038"
Idle bypass size 0.0595"
Idle economiser size 0.0571"
Idle air bleed size 0.052"
Idle port size .200"x.030"
Pri. anti-perculation bleed size (high speed) 0.028"
Sec. anti-perculation bleed size 0.031"
Sec. discharge port size 0.0635"
Sec. discharge air bleed size (side) 0.0465"
Pump jet diameter 0.033"
Carb bowl casting (0-) 1565 (stamped 1737)
Carb airhorn casting (6-) 1694
Carb choke housing casting (170-) 738
Pri. venturi cluster stamp number choke side 850
Pri. venturi cluster stamp number throttle side 851
Sec. venturi cluster stamp number choke side 846
Sec. venturi cluster stamp number throttle side 847
Metering rod part number (16-) 45
Metering rod high vacuum diameter 0.0635"
Metering rod low vacuum diameter 0.055"
Primary jet number (120-) 155
Primary jet diameter 0.091"
Secondary jet number (120-) 194
Secondary jet diameter, 0.0785"
Hot idle compensator, No

[Goatracer1]

Before going to the trouble of fixing your carb check that the choke tube INSIDE the intake manifold is not rotted out. If you are getting condensation and carbon inside your choke coil housing it can be a sign of the intake tube being rotted through. I dont mean the one connected to the carb. I am refering to the one that is INSIDE the manifold and is held in place with 2 bolts. If not corrected it will allow exhaust fumes to destroy the carb.

[GP65AT]

OK, thanks fo the requests.

As a summary I can say, I´ll buy a rebuild kit to cange all the old gaskets.
Then I´ll look if the intake tube is good or not, but I fear this could be it, because it is very sooty inside the choke housing and it also smells like exhaust gases, but I´ll check that.

If this would be so, would it be better to change to hot air choke to an electrical with an
electric choke kit which are also offered on ebay and shut down the hot air choke?

Thanks a lot
Stefan

[63gpman]

I have switched over to an electirc choke.

[Deadhead]

I am guessing that PY has the choke tubes. Not that terrible of a job to remove manifold and replace tubes. You could probably make one out of copper tubing or brake line as well.

If it has truly gone bad down in the manifold, then you will likely have to fully clean and rebuild the carb as who knows what kind of crap has gotten into it and which small passages are contaminated. Seems daunting if you have never done it before, but once you get into it, you will see it is not that bad a job. Plus, you want to get all that rusted tube junk out of the manifold so it does not get sucked down into the engine.

You can test by blowing air into it with a piece of fish tank tubing and closing the other end with your finger.

I also noticed that someone else has messed with your choke assembly. It is set at dead center and has the wrong screws for the hold-down. None of that really matters, but it means you are not the first one to have a problem with it. There are 3 different climate chokes. I found I had a cold weather hight altitude choke on one of my cars after I rebuild and could not get it to run right at start-up until I changed it.

[Goatracer1]

You don't have to remove the manifold. The tube is attached to a plate that bolts in from the top. Mine leaked and I replaced it but didnt use it. I installed an electric choke assembly from an Edelbrock carb that I had. Works great and you don't have to depend on the correct amount of heat in the manifold. Especially if you heat riser valve doesn't work. If you dont replace the tube make sure you plug both openings.

[Deadhead]

Originally Posted by Goatracer1

You don't have to remove the manifold. The tube is attached to a plate that bolts in from the top. Mine leaked and I replaced it but didnt use it. I installed an electric choke assembly from an Edelbrock carb that I had. Works great and you don't have to depend on the correct amount of heat in the manifold. Especially if you heat riser valve doesn't work. If you dont replace the tube make sure you plug both openings.

A '65 - '66 does not have this plate. It is a flared tube installed in 2 holes in the manifold unlike the earlier ones that use the plate. I had to double check on one I have off the car. Was a lot easier doing a '63 where you could unbolt the tube unit and replace.

[carbking]

In the "for what it is worth" category, these carburetors CAN be identified.

I spent thousands of hours going through original Carter prints to develop a database of numbers, so will NOT publish this database, and will not give the information away.

The numbers to acquire:

The cast (raised) number on the lower casting (right behind the throttle arm)
The cast (raised) number on the upper casting (on choke side of top)
The stamped (recessed) number on the top of the throttle side primary cluster
The stamped (recessed) number on the top of the choke side primary cluster
The stamped (recessed) number on the top of the throttle side secondary cluster
The stamped (recessed) number on the top of the choke side secondary cluster
The stamped (recessed) number on the throttle side auxilliary air valve weight
The stamped (recessed) number on the choke side auxilliary air valve weight
The stamped (recessed) number on either of the auxilliary air valve plates
The stamped (recessed) number on either of the step-up (a.k.a. metering) rods

The two casting numbers are not by themselves meaningful. These are number for casting "blanks" which may be machined different ways to use on different applications.

The stamped numbers on the venturii clusters ARE the suffix of an actual part number. Carter started codifying part numbers long before the computer. The prefix for a venturi cluster is 58. Therefore, the complete part number for the choke side primary cluster in the example given by 63GPMan is 58-850.

The stamped numbers on the auxilliary airvalve are actual part numbers for COMPONENTS of the auxilliary air valve assembly. These individual component numbers appear on the Carter prints, but NOT on the bill-of-materials for the carburetor. The part number that appears in the bill of material would be for the complete assembly.

The stamped numbers on the step-up rods are the actual part numbers. The prefix for the step-up rods is 16, which will be stamped on the rod.

Caviat: it often requires either a pair of "young eyes" or a good magnifying glass to read these stamped numbers.

Jon.

[GP65AT]

Hey Jon,

thanks for this information.
I´ll try to find all the numbers you described, maybe we can find out what type it is.

Stefan

[GP65AT]

Hey guys,

I am actually rebuilding my AFB.
I was demounting it and cleaning all the parts.
When I turned around the body of the carb, a little steel ball was falling out of it, but I am not sure where it belongs to?

I think it came out of the hole where the pump discharge check needle should be, but when I am looking at explosion drawings of the carb, ther should sit a needle and no ball
I am also not sure if the pump jet housing should look like mine, is there anythin broken on the under side of the housing??
Or are this parts all right and I can reassemble them? I do have the book rebuild edelbrock/carter carburetors, but I can´t find any detail pictures to this topic?

Thanks a lot for your help.
With best greetings
Stefan

[carbking]

What you are experiencing is just one of the issues with the parts store kits.

Carter produced 505 different AFB carburetors, the parts store kits have 1 exploded diagram (one size fits none ).

But you guessed correctly. As the AFB was used one many different size engines, pump discharge check valves of different mass are necessary to work correctly with the different engines. Carter used at least 6 different square needles and at least three different balls as pump discharge check valves.

Hopefully, the correct one for your carb is in the kit you acquired.

I have yet to see a good book on the Carter AFB carbs. Best existing information to my knowledge:

(A) Carter factory Master Parts & Service pages
(B) Rebuilding section in factory shop manual
(C) Carburetor section in the car manufacturer Master Parts Book
(D) Some of the guys that answer on these forums

Jon.
(B)

Jon.

[GP65AT]

Hey Jon,

thanks for the informations, that sounds plausible to me.
Yes there is one steel ball in the rebuild kit, I think I´ll check both weights and if necessary put in the original one.

But what is with the pump jet housing, is this alright as it is an ready to reassemble or is it broken on the one side and I have to look for a new one?

Thanks
Stefan

[carbking]

The pictured one is the way they were produced, it is not broken.

Jon.