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  1. #1
    Join Date
    Oct 2005
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    Graves County, Ky
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    78

    Carb on a 400 SBC

    I just bought a 1969 Camaro with a 400 SBC, solid cam, and headers. Automatic transmission. The car has a 600 Holley on it. I was thinking of stepping up to a 650 or 750 Holley or Barry Grant. I don't know the cam duration. Also the car has a dual plane maniforld also.

    Some suggestions would be appreciated. This is my first Camaro, and first chevrolet motor.

  2. #2
    Join Date
    Apr 2005
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    377
    Depends on what the car's purpose will be and what's in the engine?
    A low compr. 400 may like the 600.

  3. #3
    Join Date
    Oct 2004
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    If you have the hood clearance try this.

    Buy a 1" 4-hole spacer (one with lots of meat in between the bores). Cut the divider between the secondaries ONLY. In other words the rear half should look like an oval when you get done.

    It will keep a strong signal for the low end while making the carburetor appear larger (to the engine) when the secondaries open up. Only works with a dual plane intake. Shouldn't cost you more than $50.

  4. #4
    Join Date
    Oct 2005
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    Graves County, Ky
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    Thanks for the info guys I really appreciate it.

  5. #5
    Join Date
    Oct 2005
    Location
    Lincoln, NE
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    11
    750 demon, nuff said.
    '79 Malibu Pro Touring project

  6. #6
    Join Date
    Oct 2005
    Location
    Graves County, Ky
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    750 Demon? Okay, should I go double pumper or Vac Secondaries? This car is not a drag car. I want it to get up and go, but I'm not going to be racing it.

  7. #7
    Join Date
    Oct 2005
    Location
    Lincoln, NE
    Posts
    11
    you want a 750 speed demon, mech secondaries
    '79 Malibu Pro Touring project

  8. #8
    Join Date
    Oct 2004
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    Country Flag: United States
    Quote Originally Posted by JcGc
    750 Demon? Okay, should I go double pumper or Vac Secondaries? This car is not a drag car. I want it to get up and go, but I'm not going to be racing it.
    For a mostly street car that will be occasionally drag raced, a vacuum secondary is the better choice. Properly tuned it will have plenty of go. Get a quick change secondary spring kit, so you can dial in the secondaries.

    The Demon is a good carb, as it's based on the Holley design. Either will work, how much do you want to spend?

    From the Holley site:
    QUESTION How do I know if a vacuum or mechanical carburetor is best for me?
    ANSWER For street cars the vacuum secondary carburetor works best on midweight or heavyweight cars with an automatic transmission. They are more forgiving than a Double Pumper is because they work by sensing engine load. The mechanical secondary carburetor is best on a lighter car with radical camshaft and a lower gear and manual transmission or on a car that is going to be used for racing purposes.

  9. #9
    Join Date
    Oct 2005
    Location
    Graves County, Ky
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    78
    Okay here is a twist to my carb question. I have a 750 Holley sitting in a box in my garage. I took it off my boat. Before I took it off the boat, I installed a Pro Form main body, and converted the secondary to a metering block. Will this carb work okay on my engine. And if so, what size jets should I run in the primary and secondary. Also what spring would you suggest running in the vac diaphram. I hope this carb will be okay, I already have all the chrome goodies on it.

  10. #10
    Join Date
    Oct 2005
    Location
    Graves County, Ky
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    78
    Anyone?

  11. #11
    Join Date
    Oct 2004
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    Start with the Sliver spring, then go softer until it bogs when you hit it.

    As far as the jets go, that depends on too many variables. You're going to need to tune it in (either using an A/F meter, dyno, or dragstrip.

    I forget what exactly comes on them from Holley (72s front and rear?) but you could call them. Holley's are usually jetted too rich, so start there and lean it out till it slows down.

  12. #12
    Join Date
    Oct 2005
    Location
    Graves County, Ky
    Posts
    78
    amcmike,

    Thank you for the help.


  13. #13
    Join Date
    Feb 2005
    Location
    Northwest
    Posts
    126
    what is the list #, with that I can tell what stock jets were on the primary side. Probably a good place to start, proform body might make a difference though, 3310? SS