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

    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?
    This looks bad as the two rights ports are cut off. This is how a carb will line up.
    Here one side is overlapping the plenum opening and the other has a step in the flow path.
    This is on it now..

    Attached Files:

  2. 71RS6SPD

    71RS6SPD Veteran Member

    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

    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

    Feb 4, 2002
    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

    May 17, 2001
    Are they selling knockoffs of their own product? That's rediculos.
  6. 71RS6SPD

    71RS6SPD Veteran Member

    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

    Nov 4, 2004
    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

    May 4, 2001
    Las Vegas, NV
    I bet your new one is off too....
  9. 71RS6SPD

    71RS6SPD Veteran Member

    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

    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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