Check your Edelbrock Air Gap Manifold! If you have one - read this.

Discussion in 'High Performance Modifications' started by 71RS6SPD, Nov 26, 2017.

  1. 71RS6SPD

    71RS6SPD Veteran Member

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    Nov 14, 2016
    I ordered a new Edelbrock RPM Air Gap Manifold and received it a few days ago. It's going in my '71 RS 355 with a 650 DFDP. It's running pretty good now and I have a 2" Spacer under it (an improvement). The new manifold is 1" taller than the single plane Holly Street Dominator from the 70's that's coming off. So I ordered a new 1" spacer to test. I placed it on there and the main plenum ports do not line up with the spacer! Quality control? If I had just bolted it on and then mounted a carb to it I may have never known!

    I measured from the stud centers to the plenum opening on each side and and it's off by at least 3/16!". That's not good as it creates a step the flow will bounce off. You can see it in both the 2nd and 3rd picts. I have no idea how many manifolds/brands are defective in this area.. something I will now check every time.

    Summit was awesome - they did not even want to see the picts and another manifold will be here in a few days. I wonder how many of these are running down the street?
    IM.jpg
    This looks bad as the two rights ports are cut off. This is how a carb will line up.
    IMG_20171126_144849030.jpg
    Here one side is overlapping the plenum opening and the other has a step in the flow path.
    IMG_20171126_145009856.jpg
    This is on it now..
     

    Attached Files:

  2. 71RS6SPD

    71RS6SPD Veteran Member

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    Nov 14, 2016
    BTW - that 2" carb spacer was 20 bucks on amazon. I trued up the gasket surfaces with a 6" wide belt sander and machined the outside a little to make it look better. It allows quick removal for testing as the studs are the same. I have a 3" cowl hood.
     
  3. 1980RS

    1980RS Veteran Member

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    Jun 17, 2006
    That's why I call them Edelbroke from now on. Back earlier this year I bought a large port 409 intake from restoration products, that intake was so badly machined it was pitiful. I called Edelbroke, they gave me the runaround but did finally pony up and paid for the machine work to get it right. I never sell their carbs or products to anyone after that. I have fixed numerous eddy carbs along with some other stuff they make in the past. I will now only buy other manufactures intake from now on.
     
  4. Joekool

    Joekool Veteran Member

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    Hollister CA USA
    You think that's bad? I've seen them with the ports way off and not lining up with the cylinder heads very well :dumper:
     
  5. Camaro75LT

    Camaro75LT Masshole Staff Member Lifetime Gold Member

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    Boston-ish
    Are they selling knockoffs of their own product? That's rediculos.
     
  6. 71RS6SPD

    71RS6SPD Veteran Member

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    Nov 14, 2016
    I did order a replacement manifold. I will post result. JoeKool; I have been wondering about the intake port to head alignment and how to check them. I did not bother checking the one I had - UPS picked it up this AM. I will compare the next one to a gasket - and to the intake that's on there - if I do remove it. I don't think they are knock offs - sand casting is obviously not an exact science although a better job is required here. At least better quality control. I never saw a hint of this during pre-purchase research.

    I'm running a Holly 650. Took the car out yesterday (cold @ <40). It's running better than ever. Maybe its been running a bit rich. New electric choke works well. The mid range power feels awesome now and I want to be amazed with more - hence this purchase. I also ordered an autometer wide band O2 sensor and gauge to further assist in carb adjustments.
     
  7. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    Ringgold, GA
    Guess I've been lucky. I've had 3 Eddy manifolds, currently using the RPM Air-Gap, and never an issue.
     
  8. badazz81z28

    badazz81z28 Veteran Member

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    Las Vegas, NV
    I bet your new one is off too....
     
  9. 71RS6SPD

    71RS6SPD Veteran Member

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    Nov 14, 2016
    Badazz81x28 you are right! I received a new one today.. It's has a similar issue although not as bad. Off by just over an 1/8". Enough to put the plenum walls within the holes of a four hole gasket. The polish job is not as nice as the last one although I can live with that. I called Edelbrock and sent pictures. Waiting for a call back. I am thinking it will not be difficult to open up the plenum with a grinder so there are no steps in the air flow. Not sure what I will do. Edelbrock did already say 'they are not perfect".

    CorkyE : How do you like the manifold? Did it offer an improvement you can feel? Were you running a single plane?
     
  10. 71RS6SPD

    71RS6SPD Veteran Member

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    Nov 14, 2016
    CorkyE - I just want to say that it would be really easy to miss this situation if it is not checked with a 4 hole gasket on the manifold before carb install.
     

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