1965 and 1966 Nailhead AFB Carb plates - Any interest in nice 304 SS ones?

Discussion in 'Carter' started by UntamedKitty, May 17, 2015.

  1. UntamedKitty

    UntamedKitty Janitor

    Chasing a carb plate for my car led me to buy one from a reputable carb shop to find it was cheapo (Chinese?) SS that already had some rust on in, rough edges, and was magnetic. :mad: I hate crappy foreign made junk parts.

    So I am looking into making a few good ones out of 22 gauge American 304 Stainless Steel to fit my freshly rebuilt 3921S Carter AFB. This will be a four hole plate to match up to the base of the AFB holes/stock Buick manifold.
    Any Aluminum carb on a cast iron manifold where exhaust gasses circulate should have one of these. Otherwise the AL gets eaten up over time, even through the gasket.

    Also, can anyone tell me if the four holes are the same for all Buick Nailhead intake manifolds and for what years? I am trying to figure out if one plate will work for a whole bunch of applications. Thanx in advance!

  2. 66electrafied

    66electrafied Just tossing in my nickel's worth

    The AFB stuff is pretty much all the same, but the Q-Jet plate is completely different and I wasn't able to find one. The later ones (1968-70) don't fit the early 1966-67 models. I had to have the insulators at the plant I work at make me one, they were the only tin-bashers I could find that would do it. My own skills with a tin-snip aren't good enough.
  3. telriv

    telriv Founders Club Member

    Both the stainless plates for AFB & Q-Jet are available. NO NEED TO GO THROUGH THE TROUBLE OF MAKING A QUALITY PART, AS THEY ARE AVAILABLE. I have these available or can get them. A quality USA made product that DOESN'T RUST. The way we use our cars today we DON'T need these plates any longer. I'm stepping on my own toes here, just being honest. I just block the two holes in the manifold so the exhaust has NO path to crossover. Been doing this for yrs. with NO adverse affects. I don't know why some still insist on using these plates. DON'T block the ports at the heads as we still need heat in the manifold to flash the gasoline available today. The Stainless plates also get "Eaten" up & don't last FOREVER. When these plates go bad the thing that happens (worse than the base getting eaten up) is that exhaust is sucked through the choke mechanism & COMPLETELY fouls up the works. It gets SO bad that the housing can no longer be used & needs to be replaced. GOOD LUCK ON FINDING A GOOD USED ONE THAT FITS YOUR APPLICATION!!!! IF SOMEONE IS WILLING TO TAKE APART A GOOD CARB. JUST FOR ONE PART. I've had to buy complete carbs. hoping that this part ONLY was good. Have been burned a few times with sellers saying that the housing moved freely when it DIDN'T!!!!
    So, IMHO opinion blocking off the ports have MORE advantages than using the plate.

    Tom T.
  4. UntamedKitty

    UntamedKitty Janitor

    Solid info Tom and Marc, (dig that avatar Marc!)
    The numbers came back and these could be made, packaged, and delivered for about $10 each. The packing is an odd size and I estimated accounts for $2 of that. The material and quality would be significantly better than this "almost a POS" part I bought.

    But Tom has good points about blocking those passages. (especially if a gob of hi-temp silicone would do it) And I must note he has kindly pointed this out to me in the past.

    When reading about the AFB operation I thought there was something about needing that heat somewhere to make the carb work better. Any comments on that?
  5. Bigpig455

    Bigpig455 Fastest of the slow....

    Just need heat to the manifold, not the carb.

    On both spread and square bore manifolds, you can tap the holes and use a 1/4 NPY brass lug to block the carb pad heat passages. I used a little JB weld as a sealer and have never had an issue since. I still run the plate out of habit, but really don't need it anymore.
  6. 66electrafied

    66electrafied Just tossing in my nickel's worth

    My understanding is that the plates are required to prevent electrolytic corrosion caused by heat and the dissimilar metals. Yes, I used to run one without, but I found on the Nailhead Q-jet manifold you have to use one, the carb base doesn't cover up enough and will leak. The plates are supposed to be the sacrificial part; they aren't supposed to last forever. Want to see what happens when you don't use one? Look at most AFBs in a wrecker; they're all corroded out over the heat sink area. I used to have to pull about a dozen carbs to get one that was solid enough to rebuild. So sorry Tom, I'm going to have to disagree with you on this one, use the plate, even if you plug off the holes. And by the way; most of us who live in a northern climate still need chokes, they're nice to have fully functioning.
  7. telriv

    telriv Founders Club Member

    Has zero to do with the choke.
  8. Wildcat GS

    Wildcat GS Wildcat GS

    The plate is there because the exhaust gas heats the plate and that heat is transferred around all 4 throttle bores to prevent icing. That is why the plate is installed against the bottom of the carb...so the heat transfers. It also prevents direct contact of exhaust gas to the aluminum carb base which will corrode/erode the daylights out of it.
    Ray, I still run a heat riser valve and keep the exhaust crossover in tact. I would be interested in 6 of the plates if you decide to produce them. Thanks,
    Tom Mooney
  9. cobravii

    cobravii Well-Known Member

    I'd be interested in a half dozen.
  10. lapham3@aol.com

    lapham3@aol.com Well-Known Member

    Gee-I gave a fella one of my NOS 'plates' some years ago and he used that as a pattern to do these. I can't recall who right now and could well have been on the Nailhead Group=Yahoo? Anyway they came out very nice.
  11. UntamedKitty

    UntamedKitty Janitor

    Great feedback from all!

    I met with my buddy's shop and they are making up a few samples for me from my part. Is the 4-Jet manifold any different than the AFB manifold?

    The bag my plate came in had "430" written on it so I placed it on the nailhead manifold and noticed the holes placement was not dead on. There was maybe a 1/32" +/- oversize of the plate holes relative to the manifold holes. So..... here is a picture of it sitting on my '65 AFB. IMAG1769.jpg

    Does anyone know if this is normal?
    Could this be a generic plate for nailheads and the next Buick motor generation of 430s?
    Are the 401/425 carb barrel bore hole patterns different between 1965 and 1966? (besides Q-Jet of course!)

    Chime in guys, I don't want to make bad parts! UK
  12. Wildcat GS

    Wildcat GS Wildcat GS

    Ray, The 4 jet and the AFB have the same mounting bolt placement. The 4 jet does not use the plate because its base is cast iron and OK for direct contact with exhaust.
  13. UntamedKitty

    UntamedKitty Janitor

    OK, some samples are coming!

    My concern over the holes is not the mounting holes but the placement of the bore holes where they match up to the carb venturis and manifold openings.
  14. UntamedKitty

    UntamedKitty Janitor

    Got the sample parts. Much nicer than the one I bought and do not stick to a magnet!
    Still got the little overlap vs the carb base bores though, here are some pics:
    IMAG1779.jpg IMAG1777.jpg

    If you look closely, the upper right of the primary is aligned with the plate and gasket hole, but the lower left edge show a 1/16" offset. I can adjust these to line up nicer but wonder if I am just splitting hairs? Can also widen the plate overall to completely cover the carb base and two wider mounting holes. Any benefit to doing that?
    What do you guys think??? Chime in please before I cut these!
  15. telriv

    telriv Founders Club Member

    You CAN enlarge the throttle bores a little bit more so there is NO overlap. You don't want to cause any turbulence in this area as it will hinder performance some what. The edges need to COMPLETELY cover the exhaust holes on the side or they will burn through in short order.
  16. UntamedKitty

    UntamedKitty Janitor

    UPDATE: 1965 and 1966 Nailhead AFB Carb plates - Any interest in nice 304 SS ones?

    So here is whats happening!

    Had a sample plate made, did not like the plate venturi/bore holes being slightly larger than the carb. The 304 SS was just as nice as the french locks I made earlier this year though, and non-magnetic!

    Looked closer and saw the plate did not fully cover the base of the carb mating surface and where the bores were slightly off you could see the edges of some orifaces. So this was just not good enough for me to put my name on. So I took my carb to the job shop, we remeasured everything and they are making up another sample plate to check the fit again.

    Tom brought up an earlier suggestion to open up the bores a little on the carb. I did not go that route because people with bigger brains than me spent a lot of time and money designing that carb and thus opted to make the plate match the carb rather than vice a versa. Plus it dials the plate into the carb so no one else has to mess with it either!

    Question for all: Can anyone tell me if the 430 generation engine intakes use the same plate and bore sizes, or are they markedly different?
    Thanks in advance for any info!
  17. boway

    boway Active Member

    PM sent
  18. Bigpig455

    Bigpig455 Fastest of the slow....

    The 430 used a Quadrajet, so the carb flange has a spread bore configuration - much different than a square bore AFB flange.

    I would also be careful when using the carb base as a template.....something tells me using the manifold is a better idea.
  19. UntamedKitty

    UntamedKitty Janitor

    Thanx Rhett,
    Carb vs Manifold was a decision point for me!

    I decided on using the carb base because it would cover up all the recessed areas across the carb base machined face in addition to the manifold sealing areas. Another concern was if the plate stopped short of an area on the carb base sealing areas, when tightened down, there could be some deflection of the plate and/or carb. I felt that by having the extra surface area built into the plate it should minimize any potential deflections. IMAG1809.jpg IMAG1808.jpg IMAG1810.jpg IMAG1811.jpg IMAG1812.jpg
    Here we go; Left pic is carb base, note the openings, reliefs, and extent of the machines mounting surface.
    pic 2 is purchased POS SS plate.
    pic 3 is Proto 1 the good SS copy of the POS in pic 2.
    pic 4 is Proto 2 which covers the entire machined plane on carb for mounting but the holes are a touch off.
    pic 5 is the Final, covers the entire carb base mounting plane, holes are dead on, and it American Made 304 SS.

    Everything I have read and discussed tells me the carb goes on the plate, then the gasket, and onto the manifold. Hopefully it will get installed this weekend as my fresh motor just passed 900 miles of break-in. (wish me luck!)

    Well, that is the best I can come up with for my 1965 3921S AFB. I will be getting envelope and shipping prices over the weekend and offer them to who ever wants them for a flat per part delivered cost! Just like the French Locks, send me a PM and info will follow, 1st come 1st served! Many thanx to all who participated in this one, it really is the brainchild of about 25 different V8Buicks nuts!
  20. Bigpig455

    Bigpig455 Fastest of the slow....

    Looks great!

    I think you might have the order backwards..I've aways put the metal plate up against the hot exhaust gases, and then the gasket between it and the carb. But someone will weigh in here who knows, soon.

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