'66 4-Jet vs '65 AFB for a fresh '66 407 Nailhead, which is better and why?

Discussion in 'The Mixing shop.' started by UntamedKitty, Apr 19, 2015.

  1. UntamedKitty

    UntamedKitty Janitor

    Hello All,
    Never been here before but I bet some of the same wingnuts from other forums might see this post too!!!!!:grin: Chime in 'Ya-All!

    Anyhow, easy driving my fresh '66 407 Nailhead with TA's 425 cam in it and the old carb that was not rebuilt with the motor, I have found the accelerator pump not performing as needed and thus considering rebuilding this carb. I also have what I believe to be a '65 Carter AFB on a running/smoking motor that was removed from a parts car.

    I discussed this with a good Buick friend who feels the AFB would be the better choice of the two to rebuild and run. They noted the 4-Jet should have a SS plate under it too due to dissimilar metals and exhaust gas corrosion possibilities.

    So I am looking for advice before choosing which carb to rebuild, what does the community think?

    Thanx in advance for any help here!
  2. SpecialWagon65

    SpecialWagon65 Ted Nagel

  3. Gary Bohannon

    Gary Bohannon Well-Known Member

    The AFB is simple to work on and probably easier to get parts for.
    It will likely flow a little more air.
  4. telriv

    telriv Well-Known Member

    What's the AFB carb. number??? If it's a Rochester 4GC the better choice is the AFB. Flows 625 CFM's as opposed to about 475.
  5. nailheadnut

    nailheadnut Riviera addict

    If you go with the AFB, make sure that you use both the fiber and the steel gaskets. The steel gasket goes between the fiber gasket and the base of the carb. Heat goes through the steel to the aluminum base of the carb, but the corrosive gasses are kept from the aluminum base.

  6. waynek4

    waynek4 Well-Known Member

    4-jet is too small for anything bigger than a 283

    DEADMANSCURVE my first word : truck

    yeah - first thing is list both carb part #'s and a quick list of car info - car year and model , engine , trans , any mod's ? etc .
  8. UntamedKitty

    UntamedKitty Janitor

    Re: '66 4-Jet vs '65 AFB for a fresh '66 407 Nailhead,? MORE INFO

    Thank you all for the input, and I agree it is somewhat of an unfair question without more info to work with. So here are some facts to work with!
    The car is a 1966 Wildcat Conv, PS, PB, ST400, open rear, factory AC not hooked up, new dual exhaust, mild turbo mufflers, pass side damper bypassed. Fresh, complete rebuild on 401+0.030, lighter pistons, TA 425 cam with springs, Pertronix. Accelerator pump appears to be bad, carb not rebuilt with motor, little rubber boot on top of carb is all dry rotted, the car stumbles when you give it gas too fast at all rpms. This is not a race car, just a nice cruiser that gets the secondarys opened up for grins most times it is!
    4-Jet carb tag # 7026040.
    AFB carb tag # 7?????? On the silver AL tag, top casting marked 6-1743, body casting marked Carter AFB, Made In USA, 6-1721, and bottom casting corner stamped 3921S H4, top choke butterfly plate stamped 7-235, this was on a 65 401 when I got it. Bottom bores measured about 1.684 and 1.559.
    Both carb tags were a bit mangled so the numbers could be wrong. (old eyes too!)
    So that is what I know, what do you guys think and can anyone tell me anything specific about those carbs, like flow comparisons? I am not opposed to a different carb as these will not have the stock choke anymore. Or what carb would you recommend based on the info provided? Maybe add an electric choke?
    Thanx a bunch in advance for your thoughts!:laugh:
  9. dsags

    dsags Well-Known Member

    That comparison is a no brainer - its the Carter AFB hands down. The 7026040 is a 4GC Rochester and, as telriv says, flows a lot less CFM's than the Carter. The 3921S is the Carter AFB that was used on the 1965 Buick Skylark Gran Sport with automatic transmission. That had a 401 engine like the one in your Wildcat. Telriv supplied the flow information for you two carbs. Doubt if the choke has anything to do with the performance so the choice of electric versus stock is a personal choice. If you're handy rebuild kits for the AFB are readily available or Tom, telriv, could rebuild that for you.

    An alternative if originality is not important would be to use an Edelbrock carburetor. http://www.edelbrock.com/automotive/mc/carburetors/performer.shtml The 750 cfm #1411 would work fine. Not sure if the kickdown for your automatic transmission could be made to work though.

    Enjoy the summer if it ever gets here.


    DEADMANSCURVE my first word : truck

    #3921S is probably gonna work for a carb number on the carter . will check later when out in shop .
  11. telriv

    telriv Well-Known Member

    You could get an Edelbrock "750" & we can make it work. Just need to transfer throttle shafts for your kick-down, then jets, metering rods, springs, top carb. body so original air filter will fit, etc.
  12. UntamedKitty

    UntamedKitty Janitor

    Thanx for the replies, I am learning a lot here!

    Sounds like this motor can easily handle 750cfm if an Edelbrock was cost effective but that is not the case for me right now. My estimate is that the extra work needed would make this a $500 carb, ouch.

    But rebuilding the AFB would be around $50 by the time you figure in cleaners, correct rebuild kit, correct gasket/plate, etc. Which is probably about the same for the 4-Jet rebuild, maybe a little more due to the plate.

    The main benefit here would be the AFB flows significantly more than the 4-Jet and is all around a better carb to rebuild. Considering my cash flow has come to a stop recently, low cost is a must. OR, because this AFB might be something a purist GS guy needs, sell it and get something more common to save bucks?

    Am I understanding this right?

    Another question, I can most likely get a correct carb plate from a buddy and copy it, but would need to make about 25 of them to get the piece part cost down enough to make it worth while. Are people looking for these plates, or is this a "Better off just buying one on Ebay" type thing????

    DEADMANSCURVE my first word : truck

    looks like the 3921S number adds up - #3921 in carter book shows :
    65 buick
    service #4453
    1965 401 automatic
    single carb application
    always good to know . and i'll dig out my 65 service manual and see if any good info in there .
  14. UntamedKitty

    UntamedKitty Janitor

    I figured out how to empty my PM mailbox, should be good to go now! Thanx for the heads up!
  15. telriv

    telriv Well-Known Member

    You DON'T have to use the plate if you block the heat going under the carb. in the manifold. I'm NOT talking about the heat riser ports in the heads, but the 2 little holes on each side of the manifold. We DO need heat in the manifold to "flash" this cat pee called gasoline today. We don't use our cars the way they were intended originally in ALL types of weather conditions. I even remove the valve on another prone problem which is the heat riser valve on the right exhaust manifold. This ALL has NO detrimental event on the operation of the vehicle & eliminates other potential problems.
    Just more thoughts.

    Tom T.
  16. wkillgs

    wkillgs Gold Level Contributor

    The stainless heat shields are already repo'd, $19 including gasket, plus shipping.
  17. UntamedKitty

    UntamedKitty Janitor

    Saw that, and like working with Russ Martin as he is a wealth of knowledge.

    I have not seen one that has the four holes to match the carb and intake. Figured the rebuild kit would have the gasket, so does anyone know anyplace to get just a SS plate that will fully engage the gasket and carb base?

    Great input though, Thanx!
  18. bobbybuick

    bobbybuick Well-Known Member

    i put a 66 Qjet on mine and it runs perfect I just like the Quadrajet.however it would require a 66 Q-jet manifold
  19. Gary Bohannon

    Gary Bohannon Well-Known Member

    Quadrajet is by far the best for maximum gas mileage and power.
    You will need an air cleaner to match the larger air horn.
    So... intake manifold, qjet carb, and air cleaner as a package.
    (A 1966 Buick qjet will have the proper linkage for the switch pitch)
  20. UntamedKitty

    UntamedKitty Janitor

    A Q-Jet would be awesome, but my limited budget kind of knocked that one out of my reach!
    I think there might even be be a Q-Jet in the barn from a '67 Camero 327 that was stripped years back.
    Thanx anyhow!

Share This Page