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Technical tri power jet size??? sbc

Discussion in 'The Hokey Ass Message Board' started by bodymanmp, Jul 29, 2017.

  1. bodymanmp
    Joined: Dec 2, 2004
    Posts: 1,462

    bodymanmp
    Member

    running a sbc,offy 3x2 manifold,rochester carbs
    stock crate engine,8.5 compression,hei dist.
    what size should the jets be in the carbs???
     
  2. Reds 29
    Joined: Jan 16, 2006
    Posts: 435

    Reds 29
    Member

    If I remember right I have 52's in the outer carbs and 56 in the middle.
     
  3. Depends on the size of the motor and RPM's.
    ^ very close to what I have used, 55 center and 51 in the ends
     
  4. KoolKat-57
    Joined: Feb 22, 2010
    Posts: 2,876

    KoolKat-57
    Member
    from Dublin, OH

    Gee, small block Chevy......265 to well over 400 cu. in. how about a better description!
    KK
     
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  5. jimmy six
    Joined: Mar 21, 2006
    Posts: 5,154

    jimmy six
    ALLIANCE MEMBER

    It's all about the compression. 8.5 was pretty standard in 57-70's when those were used so stock jetting will be close. My 65 -283 Chevelle had 52's and it had 9-1 comp. Cubic inches doesn't have as much to do with is as most think.
    The biggest thing is you need to get on it pretty often because the outers vibrate and fill higher than the float level and cause rough running. I ran them on a 350 and loved them. They were off a 335 hp 348.
     
  6. bodymanmp
    Joined: Dec 2, 2004
    Posts: 1,462

    bodymanmp
    Member

    brand new crate 350 ci
     
  7. bodymanmp
    Joined: Dec 2, 2004
    Posts: 1,462

    bodymanmp
    Member

    ill try 55's and see what happens!!!
    i can drill them my self
     
  8. jimmy six
    Joined: Mar 21, 2006
    Posts: 5,154

    jimmy six
    ALLIANCE MEMBER

    If you go to big, solder them up and do it again. Remember drill numbers aren't jet sizes...
     
  9. rjones35
    Joined: May 12, 2008
    Posts: 865

    rjones35
    Member

    yep, I just kept drilling until I got good color on the plugs and called it good.
     
  10. Atwater Mike
    Joined: May 31, 2002
    Posts: 9,851

    Atwater Mike
    ALLIANCE MEMBER

    After drilling them, tie a piece of good cotton twine to the vise (or the front bumper if it's not a 'gasser' :D)
    about 2 feet long.
    Pass the free end of the string through the newly drilled bores, and polish them one-at-a-time, running the jet up and down the tightly held string. Works wonders:
    When I was at the Sunnyvale BMW agency, I had a number of BMW Coupe customers, inline 3.3 liter 6 cyl. with dual two-bbl carbs, sometimes came in running roughly even after carb service.
    I'd go into carbs, inspecting everything...always culminating in jet polishing (really) followed by precise linkage adjustment! 'Zooooom!'
     
  11. Countn'Carbs
    Joined: Nov 8, 2006
    Posts: 867

    Countn'Carbs
    ALLIANCE MEMBER
    from CO

    I run 57's in the primary carb and 53's in the two outboard carbs. This is on a 377 sbc.
     
  12. Rattleon
    Joined: Jan 19, 2008
    Posts: 142

    Rattleon
    Member
    from Idaho

    '65 327 10.5:1, elevation is 4500'. 55's in the primary w/51's in the dumpers. Been fighting a slight bog off idle, thinkin' accelerator pump then tryin 56's in the primary carb. Likes a little rpm before mashin' the pedal.
     

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