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Thread: Replacing sidedrafts with a Carter or Holly

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    Default Replacing sidedrafts with a Carter or Holly

    I have been looking at replacing the existing SU's on my 73 240 with a Four Barrell Aluminum Intake Manifold from ARIZONA Z CAR and using a Carter AFB #9605 or a Holly 390 600 CFM carb. Has anyone done this and can give me some advice.

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    Registered User 240ZX's Avatar
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    Default

    FWIW, stick with the SU's!!!

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    A 4 bbl makes perfect sense sitting atop a V8. On an inline 6 it makes NO sense. First the air has to make an immediate 90 degree turn once it's through the carb, and then it has to feed 6 intake ports evenly. And there's no room for a decent-flowing air filter on top of it either. A very poor choice for performance, IMO.
    Dan Baldwin
    '71 240Z 3.1, 255 rwhp
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  4. #4
    Registered User Victor Laury's Avatar
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    If you search the forums for "holley" or "Arizona Z Car" you'll find the general consence is against this set up in favor of the round top SU's

    This one is an example
    Boy am I bummed out...terrible dyno results
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    Default How about this for a little info

    We have among our datsun kind one person using dual su's on his lil 71 240Z and his 1/4 mile time is faster then mine in a turbo.

    12.8 compared to 13.5 you tell me why you would want a 4 barrel?

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    Registered User seerex's Avatar
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    if you have the flat top su units get a set of 3 or 4 screw units and just rebuild them, much better result than the holley or any 4bbl carb set up, good luck
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    Default Yea!

    What they said!
    The 1973 240Z 165540 Slightly modified. L28, 5sp, cam, headers, MSD 6AL, power windows, power door locks, leather seats, custom this and custom that.

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    I'll take everybody's word that SU's are the best, but I have the parts necessary for the 4bbl swap and I'm just curious about how differently the engine would perform....I don't have a whole bunch of hands-on experience on working with engines and I think it'd be a good learning experience. I'm also curious about triple webers: what does everybody have to say about those?

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    Registered User seerex's Avatar
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    Craig , i have read numerous threads mostly leading to the same ideal, better to sell the parts you have and go with su's 12.9 is hard to beat , the triples are wonderful for a built motor and sound wonderful , but eat alot of gas are not cheap to buy and not easy to get tuned correctly. But again they sound wonderful and you have all the gas you could ever need going into the motor, so its your money
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    Talking what everyone else said except.

    What everyone else said except a couple of things to add.

    Firstly you said you have a 73 right? in the states they are flat tops at this stage correct? If so then you want an earlier set 69-72 carbs. www.ztherapy.com hope that link works good explanation.

    Tripples are even better and webbers seem to have the biggest bragging right. However they work best on a larger camshaft profile and porting, valve work etc..

    THey are not worth while without the internal engine work.

    You can get a Z going 12.8 down the 1/4 with SU's but they will require some work. Boaring out the throats larger needles and seats and you will probably wanna do some porting to the intake manifold also.

    My opinion don't even consider anything that isn't sidedraft on a straight 6.

    PS: 1 other thing F.I is the best especially a multiple throttle body set up. The ZX injection system will probably loose you power over the SU's. But it will be a better DD.

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    Default I just read something..

    ... about the 4 bbl setup that said the carb sits 90 degrees from normal putting the primaries and secondaries side by side. The floats in this orientation, don't respond well to cornering forces.

    Also stated that the end 2 cylinders tend to run lean as the end 2 runners have a hard time getting even fuel distribution.

    I can guaranty ZTherapy's SU's will run like a scolded dog. Too many guys running them on their IT cars & just loving them.........
    Bruce Palmer
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    I am selling my Bob Sharp Racing intake and Holley 390 4 on ebay. Runs nice on my car!!

    Go to ebay and do a search for Bob Sharp Holley 4

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