Which carb gasket for the quadrajet

Discussion in ''Da Nailhead' started by EEE, Mar 29, 2009.

  1. EEE

    EEE Straight out of lo-cash!

    I picked up this q-jet intake and carb from a 66 Riviera. I'm not sure if that carburetor corresponds to the 401 or the 425 engine, so I'm trying to figure out which carburetor gasket I need to get for it. Will the basic 401 gasket still work, or do I go with the 425 gasket? It says "except carter" on one of them, so that should be the one for the q-jet then? If you look at the top left of the images you can see which size engine I did the search for.

    Many thanks for your help.
     

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  2. wkillgs

    wkillgs Gold Level Contributor

    Yes. Go for the 66-425 gasket for the Q-jet.
    Most other 66's used the Carter AFB or Rochester 4-jet.
    You will also need a metal shim gasket for the carb. It blocks off the heat passage you see in the intake.
    Contact Russ Martin for a repo one:
    http://www.nailheadbuick.com/
    or you can try to win one on eBay...
     
  3. EEE

    EEE Straight out of lo-cash!

    Took a quick trip to the garage, and it sure seems that the gasket for the 425 would be the right one, with the smaller and larger openings, instead of the openings of equal size that comes on the carter I guess.
     

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  4. EEE

    EEE Straight out of lo-cash!

  5. DaWildcat

    DaWildcat Platinum Level Contributor

    That looks like the right part. Without the stainless piece the exhaust will toast the base of the carb.

    Devon
     
  6. EEE

    EEE Straight out of lo-cash!

    Cool... That's on its way..

    Now I just need to figure out what to do for a q-jet. I have a few laying around, but none that is in very good shape. I'd like to use the original one that came with the manifold, but it feels like it needs a rebuild badly. The primaries or secondaries won't open when you pull on the throttle linkage(eh, not true, that was me talking out of my a**), and everything feels loose on it. I've seen a lot of people offer rebuild services on this board, and there seems to be quite a few places that does them. I like how this one came back all shiny and the price seems to be good too, but then JW had some words for that place which stirred everything a bit.

    http://v8buick.com/showthread.php?t=175154&highlight=rebuild+quadrajet

    Maybe send it to someone who is known to build good carbs, but charges a bit more?

    Should I go for an 800 cfm unit instead? The idea behind this carb and intake is just to get something more out of the stock nailhead, make the most out of what is around for a couple of c-notes.
     
  7. Smartin

    Smartin antiqueautomotiveservice.com Staff Member

    JW can do it for you.

    I've heard good things about Carmen Faso.
     
  8. EEE

    EEE Straight out of lo-cash!

    So this is where we are at, with the original 66 Riv carb to the left. I noticed how the fuel inlet is angled differently than the others, so that might be a fitting problem, and I also saw this on buicks.net:

    "The 4MC is a quadrajet with the choke heater coil on the side of the carb inside a housing. It is connected to heat via an insulated tube to the exaust manifold.

    A 4MV is a "divorced choke". That is, the choke coil is inside the intake manifold heat stove and controls choke action by means of a rod attached to the carb."


    "the hook-up for the trans detent/switch pitch control" ?, not sure if this is ok on the other carbs?
     

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  9. EEE

    EEE Straight out of lo-cash!

    66 Riv carb

    7026240 C6 MA
     

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  10. EEE

    EEE Straight out of lo-cash!

    73 455 carb (800cfm?)

    7043240 LA 2362
     

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  11. EEE

    EEE Straight out of lo-cash!

    72 455 carb (800 cfm?)

    7042940 ME 2431
     

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  12. EEE

    EEE Straight out of lo-cash!

    So which one makes most sense? I guess doing one of the later carbs might be more suitable for a possible 455, which might come in later once I get rich from selling meth to kids. How much would a reputable builder take to do one of these? (round figures)
     
  13. wkillgs

    wkillgs Gold Level Contributor

    Ummmm.....no. The heat passage looks different than the one on the Buick.
    I once bought a chev heat shield and it didn't cover the whole passage on the Buick. The eBay one looks even smaller. I doubt it will work.
    Call Russ Martin. He has the right one on eBay here:
    http://cgi.ebay.com/ebaymotors/Buick-66-67-carburetor-heat-shield-gasket-Q-Jet_W0QQitemZ110345428106QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item110345428106&_trksid=p3911.c0.m14&_trkparms=66%3A2|65%3A1|39%3A1|240%3A1318
    but if you buy direct, he'll sell it for less.

    I have a source that will sell you a NOS service replacement '66 Q-jet for about $260. I'll send you a PM. Do you need the Calif emissions version?
     
  14. 66electrafied

    66electrafied Just tossing in my nickel's worth

    I was having the same fun with my Q-jet assembly I got for my 401. What I did was get the original 1966 carb totally overhauled. It now has an improved needle and seat, and there are a few other little improvements that my rebuilder did to make it run more reliably that the original did. However, he was not able to get the proper manifold gasket for it. 1966 uses it's own gasket, and the '67 or later ones will not fit. I now have to get this gasket made up because no one can get it here in Canada. The tin-plate was also made up locally because the original was rusted out.

    If you use a later carb; - your choke will not work. The later Buick models used a separate choke coil mounted inside the manifold. The nailhead has no provision for this. Linkage wise, if you have a 400 switch-pitch Turbo-hydramatic, then the only other option would be the '67 carb, as it has the proper linkage to acommodate the switch-pitch switch. Here again, you've got no choke, and you'll definitely need the tin-plate cut to 1966 specs otherwise you'll get a horrible vacuum leak. The '67 and later Q-jets are narrower than the 66.

    I just found it easier to go with the 1966 carb and gasket set-up; - it cost me a fortune to get it rebuilt, but at least its "plug-and-play", and doesn't require a bunch of funny modifications to work. The ugliest part of those early carbs is the secondary-let-down diaphram; - you'll notice it's pretty much a cast piece and very much a part of that carb. The later ones are plastic and replacable. Apparently there are no rebuild kits for that diaphram, so if it's hooped, you're out of luck. Internally the older style carb uses a complicated sleave valve instead of a needle-and-seat. The Carter made Q-jets (yes, Carter built some under license for a year or so because Rochester was back-logged) use a conventional needle-and-seat, and there are retrofit kits available for Rochester made ones. Also, check and see if the throttle body base is rotted through. If it is, reject the carb, you'll never get it to seal right. Here again, this carb was unique to 1966 only, so a later base will not fit.
     

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