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Technical offenhauser dual q jet 4 barrel intake anybody seen one before

Discussion in 'The Hokey Ass Message Board' started by hot rust, Jun 30, 2022.

  1. hot rust
    Joined: Sep 18, 2007
    Posts: 724

    hot rust
    Member

    evening everyone, i purchased a offenhauser low rise dual four barrel intake today that has a quadra jet/ spread bore mounting surface the only markings that are on the intake is the offenhauser name and a circle with an I in it, i think this stands for offenhauser industries. been searching the web but no luck finding even a pic of one like it. would this maybe be a prototype that got away from the manufacturer. just curious as if anyone has seen this intake before or any such like it. 100_0423.JPG 100_0425.JPG 100_0426.JPG
     

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    Truckdoctor Andy likes this.
  2. vinfab
    Joined: Apr 18, 2006
    Posts: 262

    vinfab
    Member

    No, it is not a one off or prototype. I have seen two others over the years. Offy sometimes did things in a less than mainstream way. Case in point, here is one I have that besides this top, could be had as a square flange 2 X 4, or 3X2 Weber top . hamb4.jpg
     
    Last edited: Jun 30, 2022
  3. hot rust
    Joined: Sep 18, 2007
    Posts: 724

    hot rust
    Member

    does your intake have a part # on it? i cannot find a number at all on mine
     
  4. Fordors
    Joined: Sep 22, 2016
    Posts: 4,319

    Fordors
    Member

    I’ve seen them for Chevy big block too.
     
    lumpy 63 likes this.

  5. Fordors
    Joined: Sep 22, 2016
    Posts: 4,319

    Fordors
    Member

    Well not just Chevrolet engines, check out these old catalog listings.

    E503E206-9B5D-4AB3-98E6-F9BAAE90B3C6.jpeg 1CDD88F4-0E39-4325-9DFC-FE114AC8F068.jpeg
     
  6. vinfab
    Joined: Apr 18, 2006
    Posts: 262

    vinfab
    Member

    Mine is 5901 listed as the convertible, because the tops were available separately. I do not know what yours is, however a different version was listed as Dual Q JET High Rise Competition. The numbers for those are 5745 small blk., 5746 348, and 5747 fat blk.

    EDIT: I type too slow.
     
    Bob Lowry likes this.
  7. blowby
    Joined: Dec 27, 2012
    Posts: 8,518

    blowby
    Member
    from Nicasio Ca

  8. banjeaux bob
    Joined: Aug 31, 2008
    Posts: 6,240

    banjeaux bob
    Member
    from alaska

    I'd like to see a three Weber set up....then wonder how it ran....
     
  9. vinfab
    Joined: Apr 18, 2006
    Posts: 262

    vinfab
    Member

    I read an article on tuning cross rams years ago by Jenkins or Yunick (forget which one), that stated you needed to use the 50cc accelerator pumps for Holleys to make them work. That was with 2 carbs closer to the runners. I don't believe a single Q Jet would ever work well, I believe the fuel would fall out of suspension. I know nothing about Webers, but with 3 carbs separated and 3 accelerator pumps it had to work better than a single center located 4 barrel.
     
  10. denis4x4
    Joined: Apr 23, 2005
    Posts: 3,928

    denis4x4
    ALLIANCE MEMBER
    from Colorado

    I suspect that the Webers may have been 32/36 progressive two barrel models. Offenhauser made a lot of manifolds for four cylinder imports designed for that Weber
     
    banjeaux bob likes this.
  11. banjeaux bob
    Joined: Aug 31, 2008
    Posts: 6,240

    banjeaux bob
    Member
    from alaska

    I was thinking more on the lines of IDF downdraughts. Thanks for the reply!
     
    Hnstray likes this.
  12. jimmy six
    Joined: Mar 21, 2006
    Posts: 11,529

    jimmy six
    ALLIANCE MEMBER

    If you notice in the Offenhauser ad it says competition. These by looking are open and not dual plane like many street intakes. Many don’t like Q-jets but on the right engine 2 would look great to me. They are actually pretty compact when looking at Holleys.
     
  13. gimpyshotrods
    Joined: May 20, 2009
    Posts: 20,553

    gimpyshotrods
    ALLIANCE MEMBER

    It was three IDF's. I knew a guy that ran one in the 1990's.
    upload_2022-7-1_14-40-19.png
     
    banjeaux bob, Hnstray and vinfab like this.
  14. I don't have a pic, but there was one on a custom 59 Ford convert sitting in the bush north of here.
     
  15. hot rust
    Joined: Sep 18, 2007
    Posts: 724

    hot rust
    Member

    yea but you've got to flip the breather lid.............
     
  16. blowby
    Joined: Dec 27, 2012
    Posts: 8,518

    blowby
    Member
    from Nicasio Ca

    Had a friend with a '69 Olds 98, 455 with a Qjet and like 2:56 gears. Flipped air cleaner lid, he called it a 'CHP Tuneup'. He just loved to open up the Qjet and listen to that sound, which would go on forever while it slowly gained speed. Made him laugh every damn time. RIP Doug.
     
    scotty t, Almostdone, Fordors and 3 others like this.
  17. That is a darn cool intake. I would love to see how it would run on something. I love the Quadrajet and have had great success using them. A carb that was used on engines from a 4.3 V-6 to a 500 Cadillac is a great design, plus it was used by all of the Big 3. Besides, no other carb can make that sweet music like a Quadrajet can!
     
    AHotRod likes this.
  18. SS327
    Joined: Sep 11, 2017
    Posts: 1,133

    SS327

    That is a very rare manifold. GM designed it in 1966 and needed someone to cast a small run of them for testing. In steps Offenhouser. They cast GM’s small run of manifolds for them. GM was not impressed with the performance. They then sold the design to Offenhouser who then produced it. It was not a big seller because people were scared of the new fangled carburetor.
    Now this all happened in my head, so none of it is true, but it made for a pretty compelling story. Didn’t it?
     
    blowby and 427 sleeper like this.
  19. carbking
    Joined: Dec 20, 2008
    Posts: 3,348

    carbking
    Member

    I bought a new one for my OT Pontiac 350, and still have it in the original box.

    Planned to use two Carter thermoquads.

    Found my sheet metal skills are not sufficient to fabricate an adapter to mount to the shaker hood.

    One of two planned modifications beyond my skill set.

    Jon
     
  20. Haven’t we all done that?:)
     
  21. lemondana
    Joined: Feb 21, 2009
    Posts: 171

    lemondana
    Member
    from Lincoln NE

    It seem that you forgot about the Carter Thermoquad. Big block TQ's are slightly larger than all Q Jets, so the potential for more sweet music, as you say. carbking from above will vouch for that.
     
  22. carbking
    Joined: Dec 20, 2008
    Posts: 3,348

    carbking
    Member

    The Carter TQ was produced in sizes from 520~1000 CFM.

    I planned to use two 800's.

    Jon
     
  23. DDDenny
    Joined: Feb 6, 2015
    Posts: 16,306

    DDDenny
    Member
    from oregon

    Great story, now how about a performance report, like the cars rags did in the 60's.
     
  24. banjeaux bob
    Joined: Aug 31, 2008
    Posts: 6,240

    banjeaux bob
    Member
    from alaska

    ...and that is just what I was thinking. Thanks for the image.
     
  25. SS327
    Joined: Sep 11, 2017
    Posts: 1,133

    SS327

    Ok, so for a performance report.
    When GM was designing and testing that manifold they discovered that the quadrajet carburetors were too big. With progressive linkage the secondary’s on the front primary carb closed once the second carb started to open. This was no good for making power. When they tried to use synchronized linkage the secondaries never opened on either carb!
    Power went from 300 hp and 320 ftlbs down to 224 hp and 250 ft lbs. that was a hell of a loss!
    So GM power train decided to cut their losses and try to recoup some of the money spent and sold the design and patents to Offenhouser. GM figured they could have made decent power if they would have shrunk the size of the carbs down to about 300 cfm each and turned them into a double pumper. But at best it would have matched or made a little more power for a whole lot more money in designing, developing and patenting the new carbs.
    So this ends the saga of the dual quad spreadbore manifold. Another fine Aesop’s fairy tail!
     
    427 sleeper likes this.
  26. DDDenny
    Joined: Feb 6, 2015
    Posts: 16,306

    DDDenny
    Member
    from oregon

  27. carbking
    Joined: Dec 20, 2008
    Posts: 3,348

    carbking
    Member

    I think you have a career in writing fiction! ;) Very interesting story.

    I REALLY wanted to try mine, but as stated above, the sheet metal skills to fab the air cleaner to fit the shaker are far above my pay grade.

    It would not surprise me that Pontiac tested this intake; they tested a LOT of stuff. I have been told by an extremely reliable source inside Pontiac that they tested a 2x4 on the GTO which blew away the tripower. They also tested a 6-barrel carburetor for the GTO. But the superior 2x4 did not have the same aura for street car buyers as the tripower, and the 6-barrel was too expensive to produce. Therefore, both were rejected.

    But your basic premise about too much carb is incorrect.

    The early Q-Jets were 750 CFM, but that was 150 on the primary side, and 600 on the secondary side. The 800 CFM TQ's were 200/600.

    So the set-up would be solid linkage, NOT progressive. Two times 150 would be 300 which is less than many single 2-barrel carbs, even when you compare apples to apples on rating scales.

    The key would be making certain that the CPO orifices were identical, and use a tension scale to set the springs on the air valves. The air valves would have to open at the same rate. Difficult with springs, and one reason I prefer the AFB carbs for 2x4 set-ups.

    If the engine is capable of using the CFM on the primary side, it is impossible to over-carburate an engine using the Q-Jet or the TQ.

    I really think street manners would be terrific, depending on the efficiency of the intake design. In general, Offy dual quad intakes are far superior to Edelbrock intakes ON PONTIAC ENGINES.

    How would it perform??? Don't know, but would like to try it on my Pontiac.

    Jon
     
    Fordors, osut362, SS327 and 1 other person like this.
  28. SS327
    Joined: Sep 11, 2017
    Posts: 1,133

    SS327

    I totally made up that story. I was asked to write a fictional performance review and that’s what I did. I did not want it to sound too believable and have some one cuss me out because they could not make it work.
    Yup! Pontiac actually used dual quads on the 421 superdutys. Because the tripower sucked badly on the early ones. They were relegated to the street versions and 389s.
    In school at the tech center I got to know Dick Fleming pretty well. He worked on the Fuel Injection when he started with GM power train. Then he worked with Pontiac on cylinder heads. He told me and so did Arnie Beswick never port a Pontiac head. They were perfect right out of the box. Any little change you make will hurt flow somewhere along the power band. I guess the ports were designed on a dyno and drag strip and not on a flow bench.
    Dick also was the lead engineer for the Stage I and Stage II Buick heads. The Stage II heads were sold only over the counter and there were only 100 pair cast. His stories of racing on Woodward ave. And at 131 in Martin Michigan in the later 60s were cool as hell.
     
    carbking and Fordors like this.
  29. I saved a photo of one in the past

    Screenshot_20211020-011144_Gallery.jpg
     
    Fordors likes this.
  30. gsjohnny
    Joined: Nov 27, 2007
    Posts: 191

    gsjohnny
    Member

    if you buick stg 1 and 2 heads correct info, cruise on over to v8buick.com. they will give you more than you need. they been doing it a long time. lol
     

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