Welcome to Club Hot Rod!  The premier site for everything to do with Hot Rod, Customs, Low Riders, Rat Rods, and more. 

  •  » Members from all over the US and the world!
  •  » Help from all over the world for your questions
  •  » Build logs for you and all members
  •  » Blogs
  •  » Image Gallery
  •  » Many thousands of members and hundreds of thousands of posts! 

YES! I want to register an account for free right now!  p.s.: For registered members this ad will NOT show

 
Like Tree18Likes
  • 6 Post By NTFDAY
  • 5 Post By 53 Chevy5
  • 1 Post By NTFDAY
  • 3 Post By Hotrod46
  • 3 Post By Driver50x

Thread: carberator
          
   
   

Reply To Thread
Results 1 to 9 of 9
  1. #1
    1979chevyss is offline CHR Junior sMember Visit my Photo Gallery
    Join Date
    Mar 2020
    Location
    Angola
    Posts
    2

    Question carberator

     



    I purchased a new Q-Jet carb. for my 1979 305 elcamino and now I change out the engine for a 350 300 hp out of a 69 Camaro will the Q-JET still work and not take away power

  2. #2
    NTFDAY's Avatar
    NTFDAY is offline CHR Member Visit my Photo Gallery
    Join Date
    Aug 2003
    Location
    Springfield
    Car Year, Make, Model: '66 Mustang, 76 Corvette
    Posts
    5,206

    Quote Originally Posted by 1979chevyss View Post
    I purchased a new Q-Jet carb. for my 1979 305 elcamino and now I change out the engine for a 350 300 hp out of a 69 Camaro will the Q-JET still work and not take away power

    Properly set up the Quadrajet will out perform any other carb on a basically stock sbc
    Ken Thomas
    NoT FaDe AwaY and the music didn't die
    The simplest road is usually the last one sought
    Wild Willie & AA/FA's The greatest show in drag racing

  3. #3
    53 Chevy5's Avatar
    53 Chevy5 is offline CHR Member Visit my Photo Gallery
    Join Date
    Jan 2005
    Location
    Doon, Ia
    Car Year, Make, Model: 53 Chevy 3100
    Posts
    2,568

    I will get corrected if I'm wrong, but I think most quads are jets are good for 750 CFM. Like Ken said proper tuning is key, the problem is there's fewer and fewer people including me that know how to do that
    Seth

    God cannot give us a happiness and peace apart from Himself, because it is not there. There is no such thing. C.S.Lewis

  4. #4
    36 sedan's Avatar
    36 sedan is offline CHR Member Visit my Photo Gallery
    Join Date
    Apr 2012
    Location
    american canyon
    Car Year, Make, Model: 36 Ford Sedan, 23 T Bucket
    Posts
    1,899

    I have not worked very much with the Quadra-jet carbs, however I seem to remember they tune similarly to the Edelbrocks, with some variations such as the secondary rods for additional WOT fuel.

    Here is a link to an articles about tuning the Quadra-jet;
    http://www.northstarchevelles.com/No...ning_Paper.pdf

  5. #5
    NTFDAY's Avatar
    NTFDAY is offline CHR Member Visit my Photo Gallery
    Join Date
    Aug 2003
    Location
    Springfield
    Car Year, Make, Model: '66 Mustang, 76 Corvette
    Posts
    5,206

    Quote Originally Posted by 36 sedan View Post
    I have not worked very much with the Quadra-jet carbs, however I seem to remember they tune similarly to the Edelbrocks, with some variations such as the secondary rods for additional WOT fuel.

    Here is a link to an articles about tuning the Quadra-jet;
    http://www.northstarchevelles.com/No...ning_Paper.pdf

    The folks on the Corvette Forum consider Lars to be the guru as it pertains to Quadrajets and once I get a few things sorted out on my 76 Corvette I am going to send him my QJet for a rebuild.
    36 sedan likes this.
    Ken Thomas
    NoT FaDe AwaY and the music didn't die
    The simplest road is usually the last one sought
    Wild Willie & AA/FA's The greatest show in drag racing

  6. #6
    1979chevyss is offline CHR Junior sMember Visit my Photo Gallery
    Join Date
    Mar 2020
    Location
    Angola
    Posts
    2

    Q_jet carb.

     



    I really just need to know if there is a difference in quad for 69 to 79 because 79 had a lot of pollution and I was wondering if the 79 carb. due to that fact would reduce power

  7. #7
    NTFDAY's Avatar
    NTFDAY is offline CHR Member Visit my Photo Gallery
    Join Date
    Aug 2003
    Location
    Springfield
    Car Year, Make, Model: '66 Mustang, 76 Corvette
    Posts
    5,206

    Quote Originally Posted by 1979chevyss View Post
    I really just need to know if there is a difference in quad for 69 to 79 because 79 had a lot of pollution and I was wondering if the 79 carb. due to that fact would reduce power

    I don't believe so. The electronic controlled carbs were sometime around 82 IIRC and if I'm wrong someone will correct me. The one thing I'd do is to run an electric choke. I believe this is the one I'm using on my 76 Corvette. https://www.ebay.com/itm/Rochester-E...kAAOSwkvtb43DZ
    Ken Thomas
    NoT FaDe AwaY and the music didn't die
    The simplest road is usually the last one sought
    Wild Willie & AA/FA's The greatest show in drag racing

  8. #8
    Hotrod46's Avatar
    Hotrod46 is offline CHR Member Visit my Photo Gallery
    Join Date
    Feb 2007
    Location
    Vidalia
    Car Year, Make, Model: 1946 Ford Coupe, 1962 Austin Healey 3000
    Posts
    1,393

    There may be some power to be gained from rejetting the 79 Q-jet. The 79 engines had EGR and the mixtures jetting tended to be leaner due to the exhaust gas diluting the incoming A/F mix. Otherwise, your carb should be more than adequate for your new engine,

    I have tuned a few Q-jets and find them to be great street carbs. When well tuned, they can give mileage numbers approaching those of EFI. I probably wouldn't drag race one unless I was limited by the rules because they are difficult to rejet at the track.

    They were made in 750 and 800 (850?) CFM ratings, although some were limited in the secondary linkage to open less for smaller engines.

    BTW - You didn't ask, but I will add that a properly setup Q-jet will NOT bog when the throttle is opened. When the secondaries are set up right, the carb's air valve will just open as the engine can take the flow. The seat-of-the-pants feeling is just a continuous building of power.
    NTFDAY, glennsexton and cffisher like this.
    Mike

    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc-
    I'm following my pass​ion

  9. #9
    Driver50x's Avatar
    Driver50x is offline CHR Member Visit my Photo Gallery
    Join Date
    Jul 2016
    Location
    Saint Petersburg, Florida
    Posts
    410

    A Quadrajet is an excellent carburetor for a mild to moderate street engine.

    There are a couple important things that need to be done to it.

    One, you need to adjust the opening rate of the secondary air valve. From the factory, they usually take 4-5 seconds to open. For best performance, you want yours to open in about 1-2 seconds. To rest it, connect a Mityvac vacuum pump to the secondary air canister. Apply about 15 inches of vacuum. Release the vacuum and use a stop watch to see how long it takes for the canister to extend all the way. There is a metered orifice at the vacuum hose inlet to the canister. To adjust the opening rate, drill out the orifice with a 1/8 inch drill bit. Next, take a wooden or plastic golf tee, and cut the head off it. You will drill a small hole through the golf tee, and slide it inside the vacuum hose between the canister and the manifold vacuum source. You can try using different drill sizes until you get the opening rate that you want. I think I ended up using about a .055” drill bit with mine, I can’t remember exactly. Doing this will eliminate the famous Quadrajet “bog” that so many people complain about.

    The other important thing to do is to adjust how far the primary metering rods are inserted into the jets during cruise conditions. Late 70’s Quadrajets are the best ones to have, as this is a pretty simple adjustment on them. There is a plug from the factory that you have to remove in the top of the carburetor. This plug is directly over the power valve/primary metering rods plunger. Tap out this hole so you can install a 1/8” pipe plug in it later. Warm up the engine, and run it at cruise RPM, say about 2800 RPM. You can stick an adjustment tool down through the hole and turn the APT (adjustable part throttle) screw until you get the smoothest running and highest RPM. Now the cruise mixture is set correctly for your engine combination. This will likely be richer than it was set from the factory for the smog engine.

    There are plenty of other little adjustment you can do to fine tune a Quadrajet, but starting out with these two will get you very close. I use a Quadrajet on my Chevy 350 T Bucket, and the throttle response is fantastic. It just takes some patience and experimenting to get it right.
    NTFDAY, glennsexton and 36 sedan like this.
    Steve

Reply To Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
Links monetized by VigLink