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Thread: Which Carb to get?

  1. #1

    Default Which Carb to get?

    I have a .040" bored out 302 (306) engine in my car. Cam specs are:
    Cam lift, I/E .543"/.554"
    Duration, I/E 218°/226°
    Lobe separation @ .050 - 112°
    Heads, chamber size 60 cc
    Intake/exhaust 2.02"/1.60"
    Intake/exhaust runner 190cc/60cc

    It has a MSD ignition, aluminum heads, Cast iron exhaust manifolds with H pipe and dual exhaust (I bought it that way and don't want to spend the money for a new exhaust when this system has 1,000 miles on it), A/C (yes A/C). Timing is at 16°, all in at 2,500 RPM (34°). Has a top loader 4 speed and 3.50 gears with P215/70R15 tires. I recently installed an AEM A/F system on it. The numbers are all in the 12.2 - 13.9 range no matter how much tuning I have done to the 4160 carb. (33 shooters, 66 mains, blue cam on #2 position, standard secondary plate) 9 - 10 MPG during part throttle use. (3,000 RPM = 60 MPH on freeway.)

    I just read David Vizard's book on tuning Holley carbs. I want my engine to get the great fuel economy while still retaining available power. I'm looking for a carb that has the most tuning ability. Thanks.

  2. #2
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    Default

    What is the list number of the carb you have now? What A/F Ratio do you see while cruising? Gary
    Regards, Gary

  3. #3

    Default

    I have a 4160. 80457-12. Idle is at 12.2. Cruise speed at 2000, 2500, 3000 is between 13.2 & 13.9. Part throttle acceleration is between 11 & 12.

  4. #4
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    Your idle is at 12.2, can you not get to run leaner at idle, at least in the 13s?
    Blue pump cam is the most aggressive in the first 40°, especially in Position 2.
    You should be able to run leaner main jets until you get part throttle surge, then come back up 2 sizes, then enrich the PVCRs to compensate.
    If you can't lean out this richness, then you need a different carb.
    You should also look at other reasons for poor fuel economy, like no vacuum advance, 4 speed without overdrive, etc.
    Regards, Gary

  5. #5

    Default

    There is a problem with the current carb. I'm getting a warranty replacement this week. The reason I started this thread was to find options just in case the replacement carb is bad too.

    The problem with the current carb is, the fast idle screw is opening the primary throttle blade exposing the transition slot too much. The A/F numbers I posted are with the fast idle screw set so the transfer slot is in the recommendations made by Holley. No, I cannot lower the A/f ratio using the idle screws. this carb doesn't have the ability to modify the PVCRs. The blue pump cam was installed in an attempt to solve a off idle stumble problem and might not be correct. I'll see how the new carb works when I get it in a few days.

    I would still like to know which carb would be the best choice for this engine/car in terms of being able to tune it correctly. I want a carb with a choke and a vacuum secondary. The Demon seems to be a good carb but so does the HP, the quick fuel and brawler. I'd rather not spend a $1000 on a carb.

    I should also mention, the engine has and A/C bracket they might get in the way of a carb that has two fuel inlets. Thanks for your comments.

  6. #6
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    This would be a good choice, gives you all the tuning options, plus electric choke, vacuum secondary etc:
    https://www.holley.com/products/fuel...arts/HR-580-VS
    Regards, Gary

  7. #7

    Default

    Thanks Gaz64. I thought that would be my best choice. It looks like I won't need a new carb after all. The replacement carb came yesterday. I transferred my stuff (jets, cams, secondary spring kit) to the new carb, installed and tuned it. The engine is running better now than it ever has. A/F at cruise is 14.7 - 15. Throttle response is crisp and driveability is improved. I tried to keep the orange pump cam in it even switching to the #2 position, but this engine in this car really likes the blue cam in the #2 position. Thanks for everyone's input. I appreciate the help. Bill

  8. #8
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    Good to hear Bill. Gary
    Regards, Gary

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