Spread bore or square bore issue?

Discussion in 'Holley' started by gribbs, Dec 11, 2013.

  1. gribbs

    gribbs Well-Known Member

    I bought an 1850 600cfm Holley and it doesn't seem to mount evenly closely to my cast iron 1966 300ci stock manifold. Do I just need a simple adaptor from Holley? I am surprised it is not even a 'close' fit. man and carb.jpg
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    What carburetor was on there before? Was it a 2bbl Rochester?
     
  3. DaWildcat

    DaWildcat Platinum Level Contributor

    If the carb that came off was the old four barrel Rochester 4-Jet (4G or 4GC), it looks like a Holley square bore at first glance but bolt hole and throttle bore spacing is not the same. There may be adapters available.

    Devon
     
  4. DEADMANSCURVE

    DEADMANSCURVE my first word : truck

    yeah , I think I have a couple - will post a pic n some measurements asap . probably a part number on em also I think .
    edit : well , no part numbers , the solid one says "EELCO" , they both have some patent numbers is all . the outer holes look like they match up to holley/edelbrock , the holes just to the inside of those look like q-jet spacing . the inner holes are 3-3/4" center to center , and 3-7/8" center to center . I wrote some numbers on the one adapter also if you can make 'em out ( the 1.4 and the 1.67 are the approx. bore sizes ) . I looked in my mr.gasket catalog but did not see them . if I can find my trans-dapt catalog i'll check there also . back to the shop .
     

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    Last edited: Dec 12, 2013
  5. DEADMANSCURVE

    DEADMANSCURVE my first word : truck

    check trans-dapt #2064 . at summit its like $24 . check the notes n info - says something about drilling inner holes for small rochester ( which may mean the 4GC ) and could apply to your application .
    if jeg's lists that also they are currently running a free shipping deal - but that may not apply to canada ? summit may still be running their similar deal but that was with a $100 minimum order .
     
  6. gribbs

    gribbs Well-Known Member


    Thanks so much for the help guys!. So, it looks from here (without measuring because the manifold is outside and I don't feel like going out to the garage in the cold) that the '66 with 4 barrel option would have had an "early small Rochester 4 barrel carb" and this #2064 adapter should work by drilling in the smaller pattern to match the manifold, and then mounting my Holley to the (further outside) preset holes.

    If you don't here from me again on this, I have bought this adapter and will update once I get it home and see the final fitment. :beer
     

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