easiest way to remove the choke horn on a holley

Discussion in 'High Performance Modifications' started by muscl car, Dec 6, 2007.

  1. muscl car

    muscl car Veteran Member Lifetime Gold Member

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    Jul 8, 2001
    san bernardino calif
    i'm thinking of removing the choke horns and both my holley 660's and is there an easy way to do this . i've heard of using a hacksaw and file and also the drill press/lathe method like what we've got in our race shop . besides removing the obvious like the main body what else needs to be removed in order to prevent damage to the main body while removing the choke horn
     
  2. Vintage Musclecar

    Vintage Musclecar Veteran Member

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    Mar 19, 2004
    Union, Ohio
    Honestly, cutting off the airhorns on a Holley isn't worth the trouble unless you have a hood clearance problem and are forced to run a short filter.
     
  3. muscl car

    muscl car Veteran Member Lifetime Gold Member

    18,956
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    Jul 8, 2001
    san bernardino calif
    i'm running very small 6" dia air cleaners with 1-3/4 inch tall base plate and with 4' tall filters the choke horn looks to me like it's obstructing airflow into ea carb
     
  4. Vintage Musclecar

    Vintage Musclecar Veteran Member

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    Mar 19, 2004
    Union, Ohio
    FWIW, I've seen more carbs with air horns lopped off than I can count. I'm still waiting to see a car pick up any significant performance from the modification.

    However, if you're dead-set on doing it, the best way is to completely disassemble the carbs and have a machine shop remove the air horns with an end mill. Make sure they leave the float bowl vent boss intact. While they're at it, might as well get it out of the way and have them mill the metering block surfaces flat as well as the throttle body mounting surface. I don't care if the carbs are brand-spanking new outta-the-box units, none of those surfaces are flat from the factory.

    Eric
     
  5. Dirt Reynolds

    Dirt Reynolds Veteran Member Lifetime Gold Member

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    BC, Canada
    I ran a 3310 Holley (750 vacuum secondary) on my old 413/Vortec combo. The car went from 13.49 @ 101.8 with the stock carb to an eventual best of 12.15 @ 110.5 with the airhorn milled off and jetting changes to the secondary side. That along with a set of 275/60 BFG drag radials made the biggest improvements at the track. Milling off the airhorn made a big difference in my case.
     
  6. 69CHVL

    69CHVL Veteran Member

    The choke horn is bigger than the venturis, so the choke horn shouldnt be an issue. UNLESS - the aircleaner is right up against the choke horn. I picked up 2mph just taking off my aircleaner at the track. I have a 1.75" drop base air cleaner that's the problem, its less than an 1" from the horn.
     
  7. onovakind67

    onovakind67 Veteran Member

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    Jul 8, 2001
    Fairfield, CA
    We picked up about 8 rwhp essentially putting the air horn back on a Holley 2-bbl with a carb hat.
     
  8. Vintage Musclecar

    Vintage Musclecar Veteran Member

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    Mar 19, 2004
    Union, Ohio
    Considering the small air cleaners on there, you might...might see a performance gain by cutting off the towers, but I'd personally experiment with some sort of larger air cleaners before I started cutting up the carbs.

    [​IMG]

    As far as the HP main body conversion, I've never done it using a 660 to start with, and since the 660 uses a funky accellerator pump design (hence the name "center squirter"), I'm not sure how that would play out. Unless you added a secondary metering block at the same time, you wouldn't be able to use the rear accellerator pump system on the HP main body. Plus, the 660 baseplate isn't designed to be used with an accellerator pump linkage on the secondary side, so you'd have to swap baseplates to a standard 750 DP-style at the same time. You would also have to add a secondary float bowl that has provisions for an accellerator pump since the 660 only uses a single 50 c.c. pump on the primary side. Lastly, with the additional (required) metering block on the secondary side, you may wind up having to turn the carbs sideways on the intake to make everything fit again, which them means you'd have to re-design your throttle linkage, etc. etc. etc.

    Nice little snowball effect there just from one potential modification (HP main body), no? LOL!. ;)

    Anyhow...my advice would be to try some larger air cleaners first to see if the car runs better with them, then go from there. It's alot easier than pulling the carbs down and carving them up.

    *EDIT* last time*

    (I used the wrong formula to calculate square inches of filtering area.)
     
    Last edited: Dec 7, 2007
  9. hhott71

    hhott71 Veteran Member Lifetime Gold Member

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    Mar 30, 2001
    Joplin Mo. 64801
    That would be an interesting machining operation,
    I hope that a mill (think Bridgeport) was used instead.

    Either way. The hacksaw, die grinder, cut-off wheel, file etc method is just as effective and very cheap, only costing you time.
     
  10. Dirt Reynolds

    Dirt Reynolds Veteran Member Lifetime Gold Member

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    Jan 17, 2003
    BC, Canada
    All my runs at the track both before I milled off the choke horn and after were done without an aircleaner. It wouldn't fit with the stock, flat steel hood on my '77 with the Victor Jr.
     

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