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Ez efi surging at certain Rpm range only

Discussion in 'FAST Support Forum' started by Algamotorsports67, Mar 4, 2018.

  1. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    They were iron heads of a 305 sbc that my dad had the bigger valves installed, had them gone through again with new springs etc before the efi build
     
  2. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    What manufacturer and casting/intake runner volume? 1206 is for larger port heads. Factory Victor as supplied works good, with a good port match, using 1205 and most Chevy iron heads.

    Edit: Those are stock street fast burn 170cc intake runner heads. Use 1204-1205 with them - per Edelbrock recommendation.
     
    Last edited: Mar 8, 2018
  3. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    Gaskets matched up plenty fine had used em with these heads and block before the efi with no problems, bumping intital timing got the map in low 60s.

    Heads were hand ported to these gaskets, intake as well
     
  4. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    These heads are very restrictive. I used them many years ago where I had to comply with track rules. As I recall, the largest valves they support are 2.02/1.60. Regardless, they are too restrictive for your camshaft RPM range. Factory GM 180cc runner heads will outperform them. A low dollar set of aluminum heads with 180-195 cc intake runners would give you much improved engine performance.
     
  5. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    If you got the MAP below 65 idling in gear, you will have the ECU out of "limp home" mode. This should help some with the fuel mapping.
     
  6. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    Should I try another 2 more degrees in initial timing?
     
  7. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    I do plan on some nice heads eventually but trying to make the best I can out of what I currently have
     
  8. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    If you go too far with the initial you will get into pre-ignition just off idle. Use your vacuum gauge to watch for the highest steady vacuum, then back off two degrees.
     
    crash520 likes this.

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